Sample records for particle surface layer

  1. Layer by Layer, Nano-particle "Only" Surface Modification of Filtration Membranes

    NASA Astrophysics Data System (ADS)

    Escobar-Ferrand, Luis

    Layer by Layer (LbL) deposition using primarily inorganic silica nanoparticles is employed for the modification of polymeric micro and ultrafiltration (MF/UF) membranes to produce thin film composites (TFC) with potential nanofiltration (NF) and reverse osmosis (RO) capabilities.. A variety of porous substrate membranes with different membrane surface characteristics are employed, but exhibiting in common that wicking of water does not readily occur into the pore structure, including polycarbonate track etched (PCTE), polyethersulfone (PES) and sulfonated PES (SPEES) MF/UF membranes. Both spherical (cationic/anionic) and eccentric elongated (anionic) silica nanoparticles are deposited using conditions similar to those reported by Lee et al. Appropriate selection of the pH's for anionic and cationic particle deposition enables the construction of nanoparticle only layers 100--1200 nm in thickness atop the original membrane substrates. The surface layer thickness varies monotonically with the number of bilayers (anionic/cationic deposition cycles) as expected. The deposition process is optimized to eliminate drying induced cracking and to improve mechanical durability via thickness control and post-deposition hydro-thermal treatment. The hydrodynamic permeability of these TFC membranes is measured to evaluate their performance under typical NF operating conditions using dead-end permeation experiments and their performance compared quantitatively with realistic hydrodynamic models, with favorable results. For track etched polycarbonate MF substrates, surface modification causes a permeability reduction of approximately two orders of magnitude with respect to the bare substrates, to values comparable to those for typical commercial NF membranes. Good quantitative agreement with hydrodynamic models with no adjustable parameters was also established for this case, providing indirect confirmation that the LbL deposited surface layers are largely defect (crack) free. Imaging of our TFC membranes after permeation tests confirmed that no significant mechanical damage resulted, indicating integrity and robustness of the LbL deposited surface layers in typical applications. The selectivity of these novel TFC membranes was also tested using standard "rejection" tests normally used to characterize NF and RO membranes for their capabilities in typical applications, such as water softening or desalination. We report the dextran standards molecular weight "cut-off" (MWCO) using mixed dextrans from 1.5 to 500 KDa in dead-end stir cells, and the percentage of rejection of standard bivalent and monovalent salt solutions using steady cross flow permeation experiments. The results confirm rejection of at least 60% of even the smallest dextrans, an estimated dextran MWCO of 20 KDa, and rejection of 10% and 20% for monovalent (NaCl) and bivalent (MgSO4) salts, respectively, for all the TFC membranes studied, while the unmodified membranes showed no rejection capability at all. The work supports that nanoparticle based LbL surface modification of MF/UF membranes can produce filtration quality media for important water purification applications, such as nanofiltration (NF) softening processes, natural organic matter (NOM) elimination and possibly reverse osmosis (RO) desalination.

  2. Ti particle-reinforced surface layers in Al: Effect of particle size on microstructure, hardness and wear

    SciTech Connect

    Mordyuk, B.N., E-mail: mordyuk@imp.kiev.ua [Kurdyumov Institute for Metal Physics, 36 Academician Vernadsky Boulevard, UA-03680, Kyiv (Ukraine); Silberschmidt, V.V. [Wolfson School of Mechanical and Manufacturing Engineering, Loughborough University, LE11 3TU (United Kingdom); Prokopenko, G.I. [Kurdyumov Institute for Metal Physics, 36 Academician Vernadsky Boulevard, UA-03680, Kyiv (Ukraine); Nesterenko, Yu.V. [National Technical University 'Kyiv Polytechnic Institute', 37 Peremohy Avenue, UA-03056, Kyiv (Ukraine); Iefimov, M.O. [Frantzevich Institute for Problems of Materials Science, 3 Krzhyzhanivsky Street, UA-03142, Kyiv (Ukraine)

    2010-11-15

    Two types of Ti particles are used in an ultrasonic impact peening (UIP) process to modify sub-surface layers of cp aluminium atomized, with an average size of approx. 20 {mu}m and milled (0.3-0.5 {mu}m). They are introduced into a zone of severe plastic deformation induced by UIP. The effect of Ti particles of different sizes on microstructure, phase composition, microhardness and wear resistance of sub-surface composite layers in aluminium is studied in this paper. The formed layers of a composite reinforced with smaller particles have a highly misoriented fine-grain microstructure of its matrix with a mean grain size of 200-400 nm, while reinforcement with larger particles results in relatively large Al grains (1-2 {mu}m). XRD, SEM, EDX and TEM studies confirm significantly higher particle/matrix bonding in the former case due to formation of a Ti{sub 3}Al interlayer around Ti particles with rough surface caused by milling. Different microstructures determine hardness and wear resistance of reinforced aluminium layers: while higher magnitudes of microhardness are observed for both composites (when compared with those of annealed and UIP-treated aluminium), the wear resistance is improved only in the case of reinforcement with small particles.

  3. Influence of ionic strength on the surface charge and interaction of layered silicate particles.

    PubMed

    Liu, Jing; Miller, Jan D; Yin, Xihui; Gupta, Vishal; Wang, Xuming

    2014-10-15

    The surface charge densities and surface potentials of selected phyllosilicate surfaces were calculated from AFM surface force measurements and reported as a function of ionic strength at pH 5.6. The results show that the silica faces of clay minerals follow the constant surface charge model because of isomorphous substitution in the silica tetrahedral layer. A decreasing surface charge density sequence was observed as follows: muscovite silica face>kaolinite silica face>talc silica face, which is expected to be due to the extent of isomorphous substitution. In contrast, at pH 5.6, the alumina face and the edge surface of kaolinite follow the constant surface potential model with increasing ionic strength, and the surface charge density increased with increasing ionic strength. The cluster size of suspended kaolinite particles at pH 5.6 was found to increase with increasing ionic strength due to an increase in the surface charge density for the alumina face and the edge surface. However, the cluster size decreased at 100mM KCl as a result of an unexpected decrease in the surface charge of the alumina face. When the ionic strength continued to increase above 100mM KCl, the van der Waals attraction dominated and larger clusters of micron size were stabilized. PMID:25086721

  4. Compliant layer chucking surface

    DOEpatents

    Blaedel, Kenneth L. (Dublin, CA); Spence, Paul A. (Pleasanton, CA); Thompson, Samuel L. (Pleasanton, CA)

    2004-12-28

    A method and apparatus are described wherein a thin layer of complaint material is deposited on the surface of a chuck to mitigate the deformation that an entrapped particle might cause in the part, such as a mask or a wafer, that is clamped to the chuck. The harder particle will embed into the softer layer as the clamping pressure is applied. The material composing the thin layer could be a metal or a polymer for vacuum or electrostatic chucks. It may be deposited in various patterns to affect an interrupted surface, such as that of a "pin" chuck, thereby reducing the probability of entrapping a particle.

  5. Can Aerosol Particles Develop Organic Surface Layers Under UT\\/LS Conditions?

    Microsoft Academic Search

    L. T. Iraci; P. H. Deng

    2007-01-01

    Tropospheric aerosol particles contain oligomers and macromolecular humic-like substances that may be created by reactions in or on the surface of particles. Marine aerosols have been observed to possess surface films of fatty acids which can survive the evaporation of water from the interior of the particle. This phenomenon of surface films is of current interest with regard to their

  6. Removal of residual CuO particles on the post CMP wafer surface of multi-layered copper

    NASA Astrophysics Data System (ADS)

    Yan, Li; Ming, Sun; Xinhuan, Niu; Yuling, Liu; Yangang, He; Hailong, Li; Aochen, Wang; Hongbo, Li

    2014-04-01

    This article introduces the removal technology of CuO particles on the post CMP wafer surface of multi-layered copper. According to the Cu film corrosion curve with different concentrations of H2O2 and the effect curve of time on the growth rate of CuO film, CuO film with the thickness of 220 nm grown on Cu a surface was successfully prepared without the interference of CuCl2-2H2O. Using the static corrosion experiment the type of chelating agent (FA/O II type chelating agent) and the concentration range (10-100 ppm) for CuO removal was determined, and the Cu removal rate was close to zero. The effect of surfactant on the cleaning solution properties was studied, and results indicated that the surfactant has the effect of reducing the surface tension and viscosity of the cleaning solution, and making the cleaning agent more stable. The influence of different concentrations of FA/O I type surfactant and the mixing of FA/O II type chelating agent and FA/O I type surfactant on the CuO removal effect and the film surface state was analyzed. The experimental results indicated that when the concentration of FA/O I type surfactant was 50 ppm, CuO particles were quickly removed, and the surface state was obviously improved. The best removal effect of CuO on the copper wiring film surface was achieved with the cleaning agent ratio of FA/O II type chelating agent 75 ppm and FA/O I type surfactant 50 ppm. Finally, the organic residue on the copper pattern film after cleaning with that cleaning agent was detected, and the results showed that the cleaning used agent did not generate organic residues on the film surface, and effectively removes the organic residue on the wafer.

  7. Diffusion of gaseous products through a particle surface layer in a fluidized bed reactor

    Microsoft Academic Search

    V. N. Daggupati; G. F. Naterer; K. S. Gabriel

    2010-01-01

    This paper examines a solid conversion process during hydrolysis and decomposition of cupric chloride in a thermochemical copper–chlorine (Cu–Cl) cycle of hydrogen production. Reaction rate constants and the time required for complete solid conversion are determined by a shrinking-core model. Diffusion of gaseous reactant occurs through a film surrounding the particle, after which the reactant penetrates and diffuses through a

  8. A Method of Measuring Hydrogen Isotopes in Surface Layers of Planetary Soils by Spectroscopy of Recoil Protons in Alpha Particle Elastic Scattering

    Microsoft Academic Search

    B. N. Korchuganov; G. G. Dol'nikov; M. V. Gerasimov; O. F. Prilutskii; R. Rider; G. Waenke; T. Economou

    2004-01-01

    A theoretical and experimental feasibility study of possible determination of the hydrogen and deuterium concentrations in the surface layers of planetary bodies is presented. The method under study is the recoil proton and deuteron spectrometry of forward scattering in the course of elastic interaction of alpha particles with the nuclei of hydrogen isotopes. The spectra of recoil protons and deuterons

  9. Particle-laden boundary layers and singularities

    NASA Astrophysics Data System (ADS)

    Foster, M. R.

    2007-11-01

    The dusty-gas model for flow in dilute particle suspensions generates a singularity in particle volume fraction in a variety of viscous boundary layer problems. Such a singularity, at say x=xs along the wall, makes it impossible to continue the solution to the equations. Previously, we have found that computation of the Blasius boundary layer, with a modified equation set that permits fluid volume fraction significantly different from 1, still leads to a velocity singularity at a slightly modified location.ootnotetextFoster, Duck & Hewitt, Bull. Amer. Phys. Soc., November, 2006 Contrary to some published work, the Saffman force has not been found to mitigate the singularity for the conventional equation set, and again here, though the Saffman force does become comparable to the Stokes drag near the singularity, it alters the structure only slightly, and does not remove it. If ?o is the particle volume fraction of the fluid in which the boundary layer is embedded, then in certain re-scaled coordinates, the singularity occurs in a region ?ox?o/|?o| about xs, where a reduced set of equations applies. Within this region, there is a downstream-running ray from the origin on which ??1. However, the vertical fluid and particle velocity components are unbounded on that line. On replacing the line with a solid surface of particle material, a narrow boundary layer may be inserted, in which velocity singularities are removed.

  10. Structure and dynamics of a layer of sedimented Brownian particles

    E-print Network

    Adar Sonn Segev; Jerzy B. lawzdziewicz; Eligiusz Wajnryb; Maria L. Ekiel Jezewska; Haim Diamant; Yael Roichman

    2015-04-13

    We investigate experimentally and theoretically thin layers of colloid particles held adjacent to a solid substrate by gravity. Epifluorescence, confocal, and holographic microscopy, combined with Monte Carlo and hydrodynamic simulations, are applied to infer the height distribution function of particles above the surface, and their diffusion coefficient parallel to it. As the particle area fraction is increased, the height distribution becomes bimodal, indicating the formation of a distinct second layer. In our theory we treat the suspension as a series of weakly coupled quasi-two-dimensional layers in equilibrium with respect to particle exchange. We experimentally, numerically, and theoretically study the changing occupancies of the layers as the area fraction is increased. The decrease of the particle diffusion coefficient with concentration is found to be weakened by the layering. We demonstrate that particle polydispersity strongly affects the properties of the sedimented layer, because of particle size segregation due to gravity.

  11. Effect of temperature, atmospheric condition, and particle size on extinction in a plume of volatile aerosol dispersed in the atmospheric surface layer.

    PubMed

    Tsang, T T; Pai, P; Korgaonkar, N V

    1988-02-01

    The objective of this work is to study the effects of ambient temperature, atmospheric condition, and particle size on the extinction coefficient of diesel fuel and fog oil smoke. A first-order closure model is used to describe the turbulent diffusion of the smoke in the atmospheric surface layer. Mean values of wind speed and diffusivity in the vertical direction are obtained by the use of the Monin-Obukhov similarity theory. The 2-D crosswind line source model also includes the aerosol kinetic processes of evaporation, sedimentation, and deposition. Numerical results are obtained from simulations on a supercomputer. PMID:20523645

  12. Effect of temperature, atmospheric condition, and particle size on extinction in a plume of volatile aerosol dispersed in the atmospheric surface layer

    SciTech Connect

    Tsang, T.T.H.; Pai, P.; Korgaonkar, N.V.

    1988-02-01

    The objective of this work is to study the effects of ambient temperature, atmospheric condition, and particle size on the extinction coefficient of diesel fuel and fog oil smoke. A first-order closure model is used to describe the turbulent diffusion of the smoke in the atmospheric surface layer. Mean values of wind speed and diffusivity in the vertical direction are obtained by the use of the Monin-Obukhov similarity theory. The 2-D crosswind line source model also includes the aerosol kinetic processes of evaporation, sedimentation, and deposition. Numerical results are obtained from simulations on a supercomputer.

  13. 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.

  14. Formulation of stability-dependent empirical relations for turbulent intensities from surface layer turbulence measurements for dispersion parameterization in a lagrangian particle dispersion model

    NASA Astrophysics Data System (ADS)

    Hari Prasad, K. B. R. R.; Srinivas, C. V.; Satyanarayana, A. N. V.; Naidu, C. V.; Baskaran, R.; Venkatraman, B.

    2015-03-01

    Season- and stability-dependent turbulence intensity (? u /u *, ? v /u *, ? w /u *) relationships are derived from experimental turbulence measurements following surface layer scaling and local stability at the tropical coastal site Kalpakkam, India for atmospheric dispersion parameterization. Turbulence wind components (u', v', w') measured with fast response UltraSonic Anemometers during an intense observation campaign for wind field modeling called Round Robin Exercise are used to formulate the flux-profile relationships using surface layer similarity theory and Fast Fourier Transform technique. The new relationships (modified Hanna scheme) are incorporated in a Lagrangian Particle Dispersion model FLEXPART-WRF and tested by conducting simulations for a field tracer dispersion experiment at Kalpakkam. Plume dispersion analysis of a ground level hypothetical release indicated that the new turbulent intensity formulations provide slightly higher diffusivity across the plume relative to the original Hanna scheme. The new formulations for ? u , ? v , ? w are found to give better agreement with observed turbulent intensities during both stable and unstable conditions under various seasonal meteorological conditions. The simulated concentrations using the two methods are compared with those obtained from a classical Gaussian model and the observed SF6 concentration. It has been found that the new relationships provide comparatively higher diffusion across the plume relative to the model default Hanna scheme and provide downwind concentration results in better agreement with observations.

  15. Boundary layers in dilute particle suspensions

    NASA Astrophysics Data System (ADS)

    Foster, M. R.; Duck, P. W.; Hewitt, R. E.

    2005-11-01

    Boundary layers in dilute particle suspensions have been found to have a number of interesting features. The development of a singularity at the wall has recently been found to be common to many of these flows, ootnotetextSee Foster, Duck & Hewitt, J. Fluid Mech. 474 (2003) and Duck, Hewitt & Foster, J. Fluid Mech. 514, (2004) and we note here that Falkner-Skan-type boundary layers (layers with `edge' velocity proportional to x^m) and the boundary layer under a linearly decelerating flow ootnotetextHowarth (1934) also break down at the wall in the absence of gravity, but can be singularity-free for heavy particles. In addition, we find that matching of the Falkner-Skan profile to an outer flow is problematic for some values of m, though the case most studied heretofore---the Blasius case (for m=0)---does not feature this difficulty. Finally, a boundary layer that does not develop a singularity takes on a the typical Falkner-Skan self-similarity far downstream, in the absence of gravity. For heavy particles, however, gravity causes a constant drift of particles toward the wall, and a constant-thickness far-downstream layer. The far-downstream behavior in a light-particle suspension is different, with a particle-free zone between the wall and a particle `shock' that grows like x^(1-m).

  16. Particle motion in atmospheric boundary layers of Mars and Earth

    NASA Technical Reports Server (NTRS)

    White, B. R.; Iversen, J. D.; Greeley, R.; Pollack, J. B.

    1975-01-01

    To study the eolian mechanics of saltating particles, both an experimental investigation of the flow field around a model crater in an atmospheric boundary layer wind tunnel and numerical solutions of the two- and three-dimensional equations of motion of a single particle under the influence of a turbulent boundary layer were conducted. Two-dimensional particle motion was calculated for flow near the surfaces of both Earth and Mars. For the case of Earth both a turbulent boundary layer with a viscous sublayer and one without were calculated. For the case of Mars it was only necessary to calculate turbulent boundary layer flow with a laminar sublayer because of the low values of friction Reynolds number; however, it was necessary to include the effects of slip flow on a particle caused by the rarefied Martian atmosphere. In the equations of motion the lift force functions were developed to act on a single particle only in the laminar sublayer or a corresponding small region of high shear near the surface for a fully turbulent boundary layer. The lift force functions were developed from the analytical work by Saffman concerning the lift force acting on a particle in simple shear flow.

  17. Erosion–corrosion behavior of nano-particle-reinforced Ni matrix composite alloying layer by duplex surface treatment in aqueous slurry environment

    Microsoft Academic Search

    Jiang Xu; Chengzhi Zhuo; Dezhong Han; Jie Tao; Linlin Liu; Shuyun Jiang

    2009-01-01

    The present study concerns a duplex surface treatment of AISI 316L stainless steel to enhance the erosion–corrosion resistance. The duplex surface treatment consisted of Ni\\/nano-SiC and Ni\\/nano-SiO2 predeposited by brush plating and a subsequent surface alloying with Ni–Cr–Mo–Cu by double glow process of the substrate. Results showed that under alloying temperature (1000°C) condition, the amorphous nano-SiO2 particles still kept the

  18. Particle Generation by Ultraviolet-Laser Ablation during Surface Decontamination

    Microsoft Academic Search

    Doh-Won Lee; Meng-Dawn Cheng

    2006-01-01

    A novel photonic decontamination method was developed for removal of pollutants from material surfaces. Such a method relies on the ability of a high-energy laser beam to ablate materials from a contaminated surface layer, thus producing airborne particles. In this paper, the authors presented the results obtained using a scanning mobility particle sizer (SMPS) system and an aerosol particle sizer

  19. Kinetic double-layer model of aerosol surface chemistry and gas-particle interactions (K2-SURF): Degradation of polycyclic aromatic hydrocarbons exposed to O3, NO2, H2O, OH and NO3

    NASA Astrophysics Data System (ADS)

    Shiraiwa, M.; Garland, R. M.; Pöschl, U.

    2009-12-01

    We present a kinetic double-layer surface model (K2-SURF) that describes the degradation of polycyclic aromatic hydrocarbons (PAHs) on aerosol particles exposed to ozone, nitrogen dioxide, water vapor, hydroxyl and nitrate radicals. The model is based on multiple experimental studies of PAH degradation and on the PRA framework (Pöschl-Rudich-Ammann, 2007) for aerosol and cloud surface chemistry and gas-particle interactions. For a wide range of substrates, including solid and liquid organic and inorganic substances (soot, silica, sodium chloride, octanol/decanol, organic acids, etc.), the concentration- and time-dependence of the heterogeneous reaction between PAHs and O3 can be efficiently described with a Langmuir-Hinshelwood-type mechanism. Depending on the substrate material, the Langmuir adsorption constants for O3 vary over three orders of magnitude (Kads,O3 ? 10-15-10-13 cm3), and the second-order rate coefficients for the surface layer reaction of O3 with different PAH vary over two orders of magnitude (kSLR,PAH,O3 ? 10-18-10-17 cm2 s-1). The available data indicate that the Langmuir adsorption constants for NO2 are similar to those of O3, while those of H2O are several orders of magnitude smaller (Kads,H2O ? 10-18-10-17 cm3). The desorption lifetimes and adsorption enthalpies inferred from the Langmuir adsorption constants suggest chemisorption of NO2 and O3 and physisorption of H2O. Note, however, that the exact reaction mechanisms, rate limiting steps and possible intermediates still remain to be resolved (e.g., surface diffusion and formation of O atoms or O3- ions at the surface). The K2-SURF model enables the calculation of ozone uptake coefficients, ?O3, and of PAH concentrations in the quasi-static particle surface layer. Competitive adsorption and chemical transformation of the surface (aging) lead to a strong non-linear dependence of ?O3 on time and gas phase composition, with different characteristics under dilute atmospheric and concentrated laboratory conditions. Under typical ambient conditions, ?O3 of PAH-coated aerosol particles are expected to be in the range of 10-6-10-5. At ambient temperatures, NO2 alone does not efficiently degrade PAHs, but it was found to accelerate the degradation of PAHs exposed to O3. The accelerating effect can be attributed to highly reactive NO3 radicals formed in the gas phase or on the surface. Estimated second-order rate coefficients for O3-NO2 and PAH-NO3 surface layer reactions are in the range of 10-17-10-16 cm2 s-1 and 10-15-10-12 cm2 s-1, respectively. The chemical half-life of PAHs is expected to range from a few minutes on the surface of soot to multiple hours on organic and inorganic solid particles and days on liquid particles. On soot, the degradation of particle-bound PAHs in the atmosphere appears to be dominated by a surface layer reaction with adsorbed ozone. On other substrates, it is likely dominated by gas-surface reactions with OH or NO3 radicals (Eley-Rideal-type mechanism). To our knowledge, K2-SURF is the first atmospheric process model describing multiple types of parallel and sequential surface reactions between multiple gaseous and particle-bound chemical species. It illustrates how the general equations of the PRA framework can be simplified and adapted for specific reaction systems, and we suggest that it may serve as a basis for the development of a general master mechanism of aerosol and cloud surface chemistry.

  20. Kinetic double-layer model of aerosol surface chemistry and gas-particle interactions (K2-SURF): Degradation of polycyclic aromatic hydrocarbons exposed to O3, NO2, H2O, OH and NO3

    NASA Astrophysics Data System (ADS)

    Shiraiwa, Manabu; Garland, Rebecca M.; Pöschl, Ulrich

    2010-05-01

    We present a kinetic double-layer surface model (K2-SURF) that describes the degradation of polycyclic aromatic hydrocarbons (PAHs) on aerosol particles exposed to ozone, nitrogen dioxide, water vapor, hydroxyl and nitrate radicals [1]. The model is based on multiple experimental studies of PAH degradation and on the Pöschl-Rudich-Ammann (PRA) framework [2] for aerosol and cloud surface chemistry and gas-particle interactions. For a wide range of substrates, including solid and liquid organic and inorganic substances (soot, silica, sodium chloride, octanol/decanol, organic acids, etc.), the concentration- and time-dependence of the heterogeneous reaction between PAHs and O3 can be efficiently described with a Langmuir-Hinshelwood-type mechanism. Depending on the substrate material, the Langmuir adsorption constants for O3 vary over three orders of magnitude, and the second-order rate coefficients for the surface layer reaction of O3 with different PAH vary over two orders of magnitude. The available data indicate that the Langmuir adsorption constants for NO2 are similar to those of O3, while those of H2O are several orders of magnitude smaller. The desorption lifetimes and adsorption enthalpies suggest chemisorption of NO2 and O3 and physisorption of H2O. Note, however, that the exact reaction mechanisms, rate limiting steps and possible intermediates still remain to be resolved (e.g., surface diffusion and formation of O atoms or O3- ions at the surface). The K2-SURF model enables the calculation of ozone uptake coefficients, ?O3, and of PAH concentrations in the quasi-static particle surface layer. Competitive adsorption and chemical transformation of the surface (aging) lead to a strong non-linear dependence of ?O3 on time and gas phase composition, with different characteristics under dilute atmospheric and concentrated laboratory conditions. Under typical ambient conditions, ?O3 of PAH-coated aerosol particles are expected to be in the range of 10-6 - 10-5. At ambient temperatures, NO2 alone does not efficiently degrade PAHs, but it was found to accelerate the degradation of PAHs exposed to O3. The accelerating effect can be attributed to highly reactive NO3 radicals formed in the gas phase or on the surface. Estimated second-order rate coefficients for O3-NO2 and PAH-NO3 surface layer reactions are in the range of 10-17 - 10-16 cm2 s-1 and 10-15 - 10-12 cm2 s-1, respectively. The chemical half-life of PAHs is expected to range from a few minutes on the surface of soot to multiple hours on organic and inorganic solid particles and days on liquid particles. On soot, the degradation of particle-bound PAHs in the atmosphere appears to be dominated by a surface layer reaction with adsorbed ozone. On other substrates, it is likely dominated by gas-surface reactions with OH or NO3 radicals (Eley-Rideal-type mechanism). To our knowledge, K2-SURF is the first atmospheric process model describing multiple types of parallel and sequential surface reactions between multiple gaseous and particle-bound chemical species. It illustrates how the general equations of the PRA framework can be simplified and adapted for specific reaction systems. References: [1] Shiraiwa et al., Atmos. Chem. and Phys., 9, 9571-9586 (2009). [2] Pöschl et al., Atmos. Chem. and Phys., 7, 5989-6023 (2007).

  1. Energetic particle acceleration in shear layers

    E-print Network

    M. Ostrowski

    1999-11-05

    A plasma velocity shear layer and/or a tangential flow discontinuity provide conditions allowing for energetic particle acceleration. We review such acceleration processes acting both in non-relativistic and in relativistic flows. In heliospheric conditions shear layers can provide particles with energies compatible with the observed values (from several keV up to MeV), while in relativistic extragalactic jets proton energies even in excess of 10^{19} eV can be obtained. Application of the discussed theory to particular astrophysical objects is severely limited by inadequate knowledge of local physical conditions.

  2. Kinetic double-layer model of aerosol surface chemistry and gas-particle interactions (K2-SURF): degradation of polycyclic aromatic hydrocarbons exposed to O3, NO2, H2O, OH and NO3

    NASA Astrophysics Data System (ADS)

    Shiraiwa, M.; Garland, R. M.; Pöschl, U.

    2009-09-01

    We present a kinetic double-layer surface model (K2-SURF) that describes the degradation of polycyclic aromatic hydrocarbons (PAHs) on aerosol particles exposed to ozone, nitrogen dioxide, water vapor, hydroxyl and nitrate radicals. The model is based on multiple experimental studies of PAH degradation and on the PRA framework (Pöschl et al., 2007) for aerosol and cloud surface chemistry and gas-particle interactions. For a wide range of substrates, including solid and liquid organic and inorganic substances (soot, silica, sodium chloride, octanol/decanol, organic acids, etc.), the concentration- and time-dependence of the heterogeneous reaction between PAHs and O3 can be efficiently described with a Langmuir-Hinshelwood-type mechanism. Depending on the substrate material, the Langmuir adsorption constants for O3 vary over three orders of magnitude (Kads,O3?10-15-10-13 cm3), and the second-order rate coefficients for the surface layer reaction of O3 with different PAH vary over two orders of magnitude (kSLR,PAH,O3?10-18-10-17 cm2 s-1). The available data indicate that the Langmuir adsorption constants for NO2 are similar to those of O3, while those of H2O are several orders of magnitude smaller (Kads,H2O?10-18-10-17 cm3). The desorption lifetimes and adsorption enthalpies inferred from the Langmuir adsorption constants suggest chemisorption of NO2 and O3 - possibly in the form of O atoms - and physisorption of H2O. The K2-SURF model enables the calculation of ozone uptake coefficients, ?O3, and of PAH concentrations in the quasi-static particle surface layer. Competitive adsorption and chemical transformation of the surface (aging) lead to a strong non-linear dependence of ?O3 on time and gas phase composition, with different characteristics under dilute atmospheric and concentrated laboratory conditions. Under typical ambient conditions, ?O3 of PAH-coated aerosol particles are expected to be in the range of 10-6-10-5. At ambient temperatures, NO2 alone does not efficiently degrade PAHs, but it was found to accelerate the degradation of PAHs exposed to O3. The accelerating effect can be attributed to highly reactive NO3 radicals formed in the gas phase or on the surface. Estimated second-order rate coefficients for O3-NO2 and PAH-NO3 surface layer reactions are in the range of 10-17-10-16 cm2 s-1 and 10-15-10-12 cm2 s-1, respectively. The chemical half-life of PAH is expected to range from a few minutes on the surface of soot to multiple hours on organic and inorganic solid particles and days on liquid particles. On soot, the degradation of particle-bound PAHs in the atmosphere appears to be dominated by a surface layer reaction with adsorbed ozone. On other substrates, it is likely dominated by gas-surface reactions with OH or NO3 radicals (Eley-Rideal-type mechanism). To our knowledge, K2-SURF is the first atmospheric process model describing multiple types of parallel and sequential surface reactions between multiple gaseous and particle-bound chemical species. It illustrates how the general equations of the PRA framework can be simplified and adapted for specific reaction systems, and we suggest that it may serve as a basis for the development of a general master mechanism of aerosol and cloud surface chemistry.

  3. Optimization of laser modified surface layer homogeneity

    Microsoft Academic Search

    Anna Bien; Wieslaw Szachnowski

    1997-01-01

    The paper deals with an evaluation of homogeneity of laser modified surface layer of martensitic steel grade 21H12NMFA. The authors trying to find an optimum values of control parameters of high power laser machine with beam of which the surface layer of specimens was modified. As the examination of layer homogeneity a nondestructive electromagnetic method has been chosen. For verification

  4. Layer-by-layer polymer coating on discrete particles of cubic lyotropic liquid crystalline dispersions (cubosomes).

    PubMed

    Driever, Chantelle D; Mulet, Xavier; Waddington, Lynne J; Postma, Almar; Thissen, Helmut; Caruso, Frank; Drummond, Calum J

    2013-10-22

    Cubic phase lyotropic liquid crystalline colloidal dispersions (cubosomes) were surface-modified with seven polyelectrolyte layers using a layer-by-layer (LbL) approach. The first layer consisted of a copolymer synthesized from methacrylic acid and oleoyl methacrylate for enhanced incorporation within the bilayer of the cubic nanostructure. Six additional layers of poly(L-lysine) and poly(methacrylic acid) were then sequentially added, followed by a washing procedure to remove polymer aggregates from the soft matter particles. Polymer buildup was monitored via microelectrophoresis, dynamic light scattering, and small-angle X-ray scattering. Polymer-coated cubosomes were observed with cryo-transmission electron microscopy. A potential application of the modified nanostructured particles presented in this study is to reduce the burst-release effect associated with drug-loaded cubosomes. The effectiveness of this approach was demonstrated through loading and release results from a model hydrophilic small molecule (fluorescein). PMID:24033086

  5. Layer-by-layer surface modification of lipid nanocapsules

    Microsoft Academic Search

    Samuli Hirsjärvi; Yan Qiao; Audrey Royere; Jérôme Bibette; Jean-Pierre Benoit

    2010-01-01

    Lipid nanocapsules (LNCs) were modified by adsorbing sequentially dextran sulfate (DS) and chitosan (CS) on their surface by the layer-by-layer (LBL) approach. Tangential flow filtration (TFF) was used in intermediate purifications of the LNC dispersion during the LBL process. The surface modification was based on electrostatic interactions between the coating polyelectrolytes (PEs) and the LNCs. Therefore, a cationic surfactant, lipochitosan

  6. Improvement of Surface Layer Characteristics by Shot Lining

    Microsoft Academic Search

    Yasunori Harada

    2005-01-01

    In the present study, lining of the metal with foils using shot peening was investigated to improve the surface layer characteristics. In the shot peening experiment, the foils set on the metal are pelted with hard particles traveling at a high velocity. The foils are bonded to the metal surface due to plastic deformation induced by the collision of the

  7. Particle detection on flat surfaces

    NASA Astrophysics Data System (ADS)

    van der Donck, Jacques; Snel, Rob; Stortelder, Jetske; Abutan, Alfred; Oostrom, Sjoerd; van Reek, Sander; van der Zwan, Bert; van der Walle, Peter

    2011-04-01

    Since 2006 EUV Lithographic tools have been available for testing purposes giving a boost to the development of fab infrastructure for EUV masks. The absence of a pellicle makes the EUV reticles extremely vulnerable to particles. Therefore, the fab infrastructure for masks must meet very strict particle requirements. It is expected that all new equipment must be qualified on particles before it can be put into operation. This qualification requirement increases the need for a low cost method for particle detection on mask substrates. TNO developed its fourth generation particle scanner, the Rapid Nano. This scanner is capable of detecting nanometer sized particles on flat surfaces. The particle detection is based on dark field imaging techniques and fast image processing. The tool was designed for detection of a single added particle in a handling experiment over a reticle sized substrate. Therefore, the Rapid Nano is very suitable for the validation of particle cleanliness of equipment. During the measurement, the substrate is protected against particle contamination by placing it in a protective environment. This environment shields the substrate from all possible contamination source in the Nano Rapid (stages, elevator, cabling). The imaging takes place through a window in the protective cover. The geometry of the protective environment enables large flexibility in substrate shape and size. Particles can be detected on substrates varying from 152 x 152 mm mask substrates to wafers up to 200 mm. PSL particles of 50 nm were detected with signal noise ratio of 26. Larger particles had higher signal noise ratios. By individually linking particles in two measurements the addition of particles can be detected. These results show that the Rapid Nano is capable of detecting particles of 50 nm and larger of a full reticle substrate.

  8. Surface rheology of saponin adsorption layers.

    PubMed

    Stanimirova, R; Marinova, K; Tcholakova, S; Denkov, N D; Stoyanov, S; Pelan, E

    2011-10-18

    Extracts of the Quillaja saponaria tree contain natural surfactant molecules called saponins that very efficiently stabilize foams and emulsions. Therefore, such extracts are widely used in several technologies. In addition, saponins have demonstrated nontrivial bioactivity and are currently used as essential ingredients in vaccines, food supplements, and other health products. Previous preliminary studies showed that saponins have some peculiar surface properties, such as a very high surface modulus, that may have an important impact on the mechanisms of foam and emulsion stabilization. Here we present a detailed characterization of the main surface properties of highly purified aqueous extracts of Quillaja saponins. Surface tension isotherms showed that the purified Quillaja saponins behave as nonionic surfactants with a relatively high cmc (0.025 wt %). The saponin adsorption isotherm is described well by the Volmer equation, with an area per molecule of close to 1 nm(2). By comparing this area to the molecular dimensions, we deduce that the hydrophobic triterpenoid rings of the saponin molecules lie parallel to the air-water interface, with the hydrophilic glucoside tails protruding into the aqueous phase. Upon small deformation, the saponin adsorption layers exhibit a very high surface dilatational elasticity (280 ± 30 mN/m), a much lower shear elasticity (26 ± 15 mN/m), and a negligible true dilatational surface viscosity. The measured dilatational elasticity is in very good agreement with the theoretical predictions of the Volmer adsorption model (260 mN/m). The measured characteristic adsorption time of the saponin molecules is 4 to 5 orders of magnitude longer than that predicted theoretically for diffusion-controlled adsorption, which means that the saponin adsorption is barrier-controlled around and above the cmc. The perturbed saponin layers relax toward equilibrium in a complex manner, with several relaxation times, the longest of them being around 3 min. Molecular interpretations of the observed trends are proposed when possible. Surprisingly, in the course of our study we found experimentally that the drop shape analysis method (DSA method) shows a systematically lower surface elasticity, in comparison with the other two methods used: Langmuir trough and capillary pressure tensiometry with spherical drops. The possible reasons for the observed discrepancy are discussed, and the final conclusion is that the DSA method has specific problems and may give incorrect results when applied to study the dynamic properties of systems with high surface elasticity, such as adsorption layers of saponins, lipids, fatty acids, solid particles, and some proteins. The last conclusion is particularly important because the DSA method recently became the preferred method for the characterization of fluid interfaces because of its convenience. PMID:21894983

  9. Friction and wear behaviors of nanocrystalline surface layer of chrome–silicon alloy steel

    Microsoft Academic Search

    D. M. Ba; S. N. Ma; F. J. Meng; C. Q. Li

    2007-01-01

    A nanocrystalline surface layer of about 25 ?m thickness was fabricated on a quenched and tempered chrome–silicon alloy steel using Supersonic Fine Particles Bombardment (SFPB). The microstructural features in the treated surface layer were characterized using scanning electron microscopy and transmission electron microscopy observations. The grain size is about 16 nm in the top surface layer. Nanoindentation tests indicate the hardness of

  10. Subnanometer Palladium Particles Synthesized by Atomic Layer Deposition

    SciTech Connect

    Feng, Hao P. [Argonne National Lab. (ANL), Argonne, IL (United States); Libera, Joseph A. [Argonne National Lab. (ANL), Argonne, IL (United States); Stair, Peter C. [Northwestern Univ., Evanston, IL (United States); Miller, Jeffrey T. [Argonne National Lab. (ANL), Argonne, IL (United States); Elam, Jeffrey W. [Argonne National Lab. (ANL), Argonne, IL (United States)

    2011-06-03

    Monodispersed palladium nanoparticle catalysts were synthesized by atomic layer deposition (ALD) using alternating exposures of Pd hexafluoroacetylacetonate (Pd(hfac)?) and formalin on an alumina support. The size of the ALD Pd particles could be tuned by adjusting the preparation conditions. Conventional ALD conditions produced Pd particles with an average size of 1.4 nm. Removal of surface hydroxyls from the alumina support by a chemical treatment using trimethyl aluminum (TMA) before performing Pd ALD led to nanoparticles larger than 2 nm. Ultrasmall (subnanometer) Pd particles were synthesized using low-temperature metal precursor exposures, followed by applying protective ALD alumina overcoats. The ALD Pd particles were characterized by transmission electron microscopy, extended X-ray absorption fine structure, and diffuse reflectance infrared Fourier transform spectroscopy techniques. The Pd loadings were measured by X-ray fluorescence. The catalytic performance of ALD Pd particles of different sizes was compared in the methanol decomposition reaction. The specific activity (normalized by Pd loading) of the ultrasmall Pd particles was higher than those of the larger particles. Considering the metal dispersion factor, the turnover frequency (TOF) of the ultrasmall Pd particles is comparable to that of the medium-sized (1.4 nm, on average) Pd particles synthesized under standard ALD conditions. The large Pd particles (>2 nm) are a factor of 2 less active than the smaller Pd particles.

  11. Structure analysis of layer-by-layer multilayer films of colloidal particles

    NASA Astrophysics Data System (ADS)

    Batys, Piotr; Nosek, Magdalena; Wero?ski, Pawe?

    2015-03-01

    We have mimicked the layer-by-layer self-assembling process of monodisperse colloidal particles at a solid-liquid interface using the extended random sequential adsorption model of hard spheres. We have studied five multilayer structures of similar thickness, each created at a different single-layer surface coverage. For each multilayer, we have determined its particle volume fraction as a function of distance from the interface. Additionally, we have characterized the film structure in terms of 2D and 3D pair-correlation functions. We have found that the coverage of about 0.3 is optimal for producing a uniform, constant-porosity multilayer in a minimum number of adsorption cycles. The single-layer coverage has also a significant effect on the primary maximum of 2D radial distribution function. In the case of multilayer with the coverage lower than 0.30 the 2D pair-correlation functions of even layers exhibit maxima decreasing with the increase in the layer number. We have verified our theoretical predictions experimentally. We have used fluorescence microscopy to determine the 2D pair-correlation functions for the second, third, and fourth layers of multilayer formed of micron-sized spherical latex particles. We have found a good agreement between our theoretical and experimental results, which confirms the validity of the extended RSA model.

  12. Carbides composite surface layers produced by (PTA)

    SciTech Connect

    Tajoure, Meloud, E-mail: Tajoore2000@yahoo.com [MechanicalEng.,HIHM,Gharian (Libya); Tajouri, Ali, E-mail: Tajouri-am@yahoo.com, E-mail: dr.mokhtarphd@yahoo.com; Abuzriba, Mokhtar, E-mail: Tajouri-am@yahoo.com, E-mail: dr.mokhtarphd@yahoo.com [Materials and Metallurgical Eng., UOT, Tripoli (Libya); Akreem, Mosbah, E-mail: makreem@yahoo.com [Industrial Research Centre,Tripoli (Libya)

    2013-12-16

    The plasma transferred arc technique was applied to deposit a composite layer of nickel base with tungsten carbide in powder form on to surface of low alloy steel 18G2A type according to polish standard. Results showed that, plasma transferred arc hard facing process was successfully conducted by using Deloro alloy 22 plus tungsten carbide powders. Maximum hardness of 1489 HV and minimum dilution of 8.4 % were achieved by using an arc current of 60 A. However, when the current was further increased to 120 A and the dilution increases with current increase while the hardness decreases. Microstructure of the nickel base deposit with tungsten carbide features uniform distribution of reinforcement particles with regular grain shape half - dissolved in the matrix.

  13. Particle assembly on surface features (patterned surfaces).

    PubMed

    Adamczyk, Zbigniew; Barbasz, Jakub; Zembala, Maria

    2007-05-01

    Irreversible adsorption (deposition) of spherical particles on surface features of various shapes (collectors) was studied using the random sequential adsorption (RSA) model. The collectors in the form of linear line segments, semicircles, and circles were considered. Numerical simulation of the Monte Carlo type enabled one to determine particle configurations, the jamming coverage, and the end to end length of particle monolayers for various collector length (L) to particle size (d) ratio L = L/d. It was revealed that the jamming coverage for linear collectors Theta'(infinity) increases for L > 2 according to a linear dependence with respect to 1/L. For 2 > L > 1, a parabolic dependence of Theta'(infinity) on 1/L was predicted, characterized by the maximum value of Theta'(infinity) = 1.125 for L = 4/3. These dependencies allowed one to formulate an equation determining the length of nanostructures on surfaces if the averaged number of adsorbed particles is known. It was also predicted that the end to end length of the monolayer on a linear collector /L increased linearly with 1/L for L > 2. For 2 > L > 1 the dependence of /L on L was approximated by a polynomial expression, exhibiting a maximum of /L = 1.17 for L = 1.45. In the case of circular collectors, the jamming coverage was found to be substantially smaller for the same value of 1/L. It was demonstrated that the theoretical results are in agreement with our preliminary experimental data obtained for latex particles adsorbing on polyelectrolyte modified mica and on patterned surfaces obtained by a polymer-on-polymer stamping technique of gold covered silicon (Zheng et al. Langmuir 2002, 18, 4505). PMID:17408296

  14. Cloaking of 2D particle geometries in a surface medium

    NASA Astrophysics Data System (ADS)

    Alexopoulos, A.; Yau, K. S. B.

    2013-06-01

    We theoretically examine the cloaking condition for two-dimensional particles with varying geometry embedded inside a surface medium. General solutions are obtained for multi-layer particle configurations with either all positive or partially negative constitutive parameters respectively. Cloaking of particle geometries that are large relative to the incident wavelength is demonstrated. Theoretical predictions are compared to full-wave numerical simulations for arrays of particles consisting of different geometries.

  15. Onset of new particle formation in boundary layer

    NASA Astrophysics Data System (ADS)

    Manninen, Hanna E.; Lampilahti, Janne; Mirme, Sander; Nieminen, Tuomo; Ehn, Mikael; Pullinen, Iida

    2014-05-01

    At this moment, the mechanisms of atmospheric new particle formation (NPF), and the vapors participating in this process are not truly understood. Especially, in which part of the atmosphere the NPF takes place, is still an open question. To detect directly the very first steps of NPF in the atmosphere, we measured these chemical and physical processes within the Planetary Boundary Layer (PBL). We used airborne Zeppelin and Cessna measurements, and ground based in-situ measurements. Using Zeppelin, we focused on the time of the development of the PBL (altitudes up to 1 km) from sunrise until noon to measure vertical profiles of aerosol particles and chemical compounds. This is also the time when NPF typically occurs at ground level. On summer 2012, Zeppelin was measuring nucleation occurring in the polluted Po Valley area, Northern Italy, especially over the San Pietro Capofiume field site. A year later, Zeppelin had a spring campaign in boreal forest area, close to Hyytiälä field site in Southern Finland. During both campaigns, we aimed on measuring the vertical and the horizontal extension for NPF events using an instrumented Zeppelin. The vertical profile measurements represent the particle and gas concentrations in the lower parts of the atmosphere: the residual layer, the nocturnal boundary layer, and the PBL. At the same time, the ground based measurements records present conditions in the surface layer. The key instruments to measure the onset of NPF were an Atmospheric Pressure interface Time-Of-Flight mass spectrometer (APi-TOF), a Particle Size Magnifier (PSM), and a Neutral cluster and Air Ion Spectrometer (NAIS). These instruments are able to measure particles at the size range ~1-2 nm where atmospheric nucleation and cluster activation takes place. The onset of NPF was usually observed onboard Zeppelin when it was measuring inside the rising mixed layer which is connected to the surface layer by effective vertical mixing. The newly formed, subsequently growing, particles were observed to be homogeneously distributed inside the mixed layer. These measurements are part of the PEGASOS project which aims to quantify the magnitude of regional to global feedbacks between the atmospheric chemistry and physics, and thus quantify the changing climate.

  16. Laser-Based Transient Surface Acceleration of Thermoelastic Layers

    NASA Astrophysics Data System (ADS)

    CETINKAYA, CETIN; WU, CUNLI; LI, CHEN

    2000-03-01

    The removal of particles from elastic substrates has been an important practical problem in the electronics industry especially as the sizes of electronic units shrink. In recent years, there has been an interest in removingsubmicron level particles from surfaces. The use of traditional surface cleaning methods, such as ultrasonically induced fluid flow, vibrational methods, centrifugal techniques, is limited to particles that require surface acceleration lower than 107m/s2. For the effective removal of submicron particles, a higher level surface acceleration is needed since the adhesion forces (mainly van der Waals force for dry surfaces) are related to the particle size and increase approximately linearly as the characteristic radius of small particles that are to be removed decreases. In current work, based on the generalized dynamic theory of thermoelasticity reported, a transfer matrix formulation including the second sound effect is developed for a thermoelastic layer. The transfer matrix for axisymmetric wave propagation in a thermoelastic layer is obtained by adopting a double integral transform approach. The second sound effect is included to eliminate the thermal wave travelling with infinite velocity as predicted by the diffusion heat transfer model, and, consequently, the immediate arrival of waves. Using the current formulation and the periodic systems framework, a transfer function formulation for calculating the accelerations is developed for transient analysis. A double integral transform inversion method is used for transient response calculations. Acceleration levels, sufficient for submicron particle removal, are reported. Various processes such as thermoelastic stresses, surface evaporation, and optical breakdown may be responsible for surface acceleration components and particle removal. In current work, only the surface acceleration due to transient thermoelastic wave propagation is under investigation.

  17. Layer-by-layer surface modification of lipid nanocapsules.

    PubMed

    Hirsjärvi, Samuli; Qiao, Yan; Royere, Audrey; Bibette, Jérôme; Benoit, Jean-Pierre

    2010-10-01

    Lipid nanocapsules (LNCs) were modified by adsorbing sequentially dextran sulfate (DS) and chitosan (CS) on their surface by the layer-by-layer (LBL) approach. Tangential flow filtration (TFF) was used in intermediate purifications of the LNC dispersion during the LBL process. The surface modification was based on electrostatic interactions between the coating polyelectrolytes (PEs) and the LNCs. Therefore, a cationic surfactant, lipochitosan (LC), was synthesised by coupling stearic anhydride on chitosan, and the surface of LNCs was first modified by this LC by the post-insertion technique. The PEs could be successfully adsorbed on the LNC surface as verified by alternating zeta potential and increase in size. To present a therapeutic application, fondaparinux sodium (FP), a heparin-like synthetic pentasaccharide, was introduced on the LNC surface instead of DS. PMID:20656028

  18. Friction microprobe investigation of particle layer effects on sliding friction

    SciTech Connect

    Blau, P.J.

    1993-01-01

    Interfacial particles (third-bodies), resulting from wear or external contamination, can alter and even dominate the frictional behavior of solid-solid sliding in the absence of effective particle removal processes (e.g., lubricant flow). A unique friction microprobe, developed at Oak Ridge National Laboratory, was used to conduct fine- scale friction studies using 1.0 mm diameter stainless steel spheres sliding on several sizes of loose layers of fine aluminum oxide powders on both aluminum and alumina surfaces. Conventional, pin-on-disk experiments were conducted to compare behavior with the friction microprobe results. The behavior of the relatively thick particle layers was found to be independent of the nature of underlying substrate, substantiating previous work by other investigators. The time-dependent behavior of friction, for a spherical macrocontact starting from rest, could generally be represented by a series of five rather distinct phases involving static compression, slider breakaway, transition to steady state, and dynamic layer instability. A friction model for the steady state condition, which incorporates lamellar powder layer behavior, is described.

  19. Determination of physical and dynamic properties of suspended particles in water column with ultrasonic scanning in between the water surface and stable sediment layer.

    NASA Astrophysics Data System (ADS)

    Acar, Dursun; Alpar, Bedri; Ozeren, Sinan; Cagatay, Nam?k; Sari, Erol; Vardar, Denizhan; Eris, Kadir

    2015-04-01

    The behavior of seafloor sediment with its water column should be known against any occurrences of anoxic or oxic conditions. The most important ones of these conditions are possible leakage of natural gas or escape of liquids from sediment. On the basis of combined solid/liquid flow dynamics in sedimentation, such kind of events can change, even in an effective manner, the dynamic movements of molecules and their cumulative mass of particules, i.e. the suspended materials. The deployment of suitable sediment traps or ultrasonic transducers somewhere in the water column are not easy attempts in order to obtain useful information about the state of suspended materials during sedimentation. These are usually bulky instruments; therefore they may behave like an anti-move suppresser on the particles moving in the float direction, in oxic and anoxic manner. These instruments, on the other hand, may cover the effects of diffusive flow or bubble formed gas and fluid escape from the sediment surface into the water column. Ultrasonic scanners, however, are able to make observations in a remote manner, without affecting such artificial events. Our field trials were successfully completed at the historical estuary called Halic of Marmara sea . The physical properties; such as the velocity of particles, their travel directions, their dimensions and the ability to observe anti-compositor crushes of shock waves of the bubbles are only a few of these observations in natural ambience. The most important problem solved about water pressure during 3 atmosphere . The sensor has been tested successfully few times. We used the ''High voltage electric isolator oil filling'' to the inside of the scanner for pressure equalization between outer side and inner body of probe at a depth of (20 meters) beneath the sea surface . The transmitted signals by the planar crystal of the transducer become weaker under the pressure of overlying water column in depths. Our efforts are now focused on the improved performance of transducer at higher than over 3 atm pressure. Keywords: ultrasonic , flow , particle , Sediment , Cumulative mass

  20. Regulation of Surface Potentialat Amphoteric Surfaces during Particle-Particle Interaction

    E-print Network

    Chan, Derek Y C

    Regulation of Surface Potentialat Amphoteric Surfaces during Particle-Particle Interaction BY D and constant potential assumptions and is applicable to oxide colloids and amphoteric biosurfaces in particular

  1. Effect of surface ionization on wetting layers

    NASA Technical Reports Server (NTRS)

    Kayser, R. F.

    1986-01-01

    A surface ionization model due to Langmuir is generalized to liquid mixtures of polar and nonpolar components in contact with ionizable substrates. When a predominantly nonpolar mixture is near a miscibility gap, thick wetting layers of the conjugate polar phase form on the substrate. Such charged layers can be much thicker than similar wetting layers stabilized by dispersion forces. This model may explain the 0.4- to 0.6-micron-thick wetting layers formed in stirred mixtures of nitromethane and carbon disulfide in contact with glass.

  2. Surface layering properties of Intralipid phantoms

    NASA Astrophysics Data System (ADS)

    Bodenschatz, Nico; Krauter, Philipp; Foschum, Florian; Nothelfer, Steffen; Liemert, André; Simon, Emanuel; Kröner, Sabrina; Kienle, Alwin

    2015-02-01

    Intralipid has become an extensively studied and widely used reference and calibration phantom for diffuse optical imaging technologies. In this study we call attention to the layering properties of Intralipid emulsions, which are commonly assumed to have homogeneous optical properties. By measurement of spatial frequency domain reflectance in combination with an analytical solution of the radiative transfer equation for two-layered media, we make quantitative investigations on the formation of a surface layer on different dilutions of Intralipid. Our findings are verified by an independent spatially resolved reflectance setup giving evidence of a time dependent, thin and highly scattering surface layer on top of Intralipid-water emulsions. This layer should be considered when using Intralipid as an optical calibration or reference phantom.

  3. Texturing Implicit Surfaces with Particle Systems Introduction

    E-print Network

    particle trajectory with T . The support surface T should be simple enough so that it is very easy whether a particle trajectory has crossed the support surface. If it has, then we obtain the textureTexturing Implicit Surfaces with Particle Systems Introduction We describe an intuitive yet

  4. Texturing Implicit Surfaces with Particle Systems Introduction

    E-print Network

    on the surface is "read" at the intersection of the corresponding particle trajectory with T. The support surface approximation of the implicit surface. Next, particle trajectories are generated by numeric integration of the motion equation. At each integration step, we test whether a particle trajectory has crossed the support

  5. Where surface physics and fluid dynamics meet: rupture of an amphiphile layer by fluid flow

    E-print Network

    Mahesh Bandi; Walter Goldburg; John Cressman Jr.; Hamid Kellay

    2006-07-19

    We investigate the fluctuating pattern created by a jet of fluid impingent upon an amphiphile-covered surface. This microscopically thin layer is initially covered with 50 $\\mu$m floating particles so that the layer can be visualized. A vertical jet of water located below the surface and directed upward drives a hole in this layer. The hole is particle-free and is surrounded by the particle-laden amphiphile region. The jet ruptures the amphiphile layer creating a particle-free region that is surrounded by the particle-covered surface. The aim of the experiment is to understand the (fluctuating) shape of the ramified interface between the particle-laden and particle-free regions.

  6. Particle-Surface Interaction Model and Method of Determining Particle-Surface Interactions

    NASA Technical Reports Server (NTRS)

    Hughes, David W. (Inventor)

    2012-01-01

    A method and model of predicting particle-surface interactions with a surface, such as the surface of a spacecraft. The method includes the steps of: determining a trajectory path of a plurality of moving particles; predicting whether any of the moving particles will intersect a surface; predicting whether any of the particles will be captured by the surface and/or; predicting a reflected trajectory and velocity of particles reflected from the surface.

  7. Humidity variations in the atmospheric surface layer 

    E-print Network

    Humphrey, Scott Richard

    1985-01-01

    . James , Sc ns (Head of Department) May 1985 ABSTRACT Humidity Uariati'ons in the Atmospheric Surface Layer. (May 1985) Scott Richard Humphrey, B. S. , Texas A8M University Chairman of Advisory Committee: Dr. James R. Scoggins The turbulent... fluctuations of humidity in the atmospheric surface layer are stud1ed using field data consist1ng of h1gh frequency w1nd velocity, temperature, and humidity measurements collected using a 22 m micrometeorolog1cal tower instrumented at three levels...

  8. Extending the Diffuse Layer Model of Surface Acidity Constant Behavior: IV. Diffuse Layer Charge/Potential Relationships

    EPA Science Inventory

    Most current electrostatic surface complexation models describing ionic binding at the particle/water interface rely on the use of Poisson - Boltzmann (PB) theory for relating diffuse layer charge densities to diffuse layer electrostatic potentials. PB theory is known to contain ...

  9. Characterization of the Martian Surface Layer

    Microsoft Academic Search

    F RANCISCOVALERO GERMÁNMARTÍNEZ

    The authors have estimated the diurnal evolution of Monin-Obukhov length, friction velocity, tempera- ture scale, surface heat flux, eddy-transfer coefficients for momentum and heat, and turbulent viscous dissipation rate on the Martian surface layer for a complete sol belonging to the Pathfinder mission. All these magnitudes have been derived from in situ wind and temperature measurements at around 1.3-m height

  10. Subwavelength particle layers for improved light outcoupling of OLEDs

    Microsoft Academic Search

    Helmut Bechtel; Wolfgang Busselt; Joachim Opitz

    2004-01-01

    Subwavelength silica particle layers have been applied between glass and thin film luminescent layers of Alq3 and a polymer MEH-PPV layer, respectively. The layers acted as a randomised two-dimensional diffraction lattice, which increased the fraction of emitted power from thin film organic layers into air. In contrast to perfectly ordered structures strong interference emission patterns did not occur. Still, an

  11. Development of Encoded Particle-Polymer Arrays for the Accelerated Screening of Antifouling Layers

    PubMed Central

    Kithva, Prakash; Bax, Jacinda; Surawski, Peter P.T.; Montero, Michael J.

    2012-01-01

    A multiplexed screening methodology for the rapid development of antifouling polymer surfaces is presented. An array of protein resistant polymer layers with high grafting (>100 mg/m2) were polymerized on optically encoded particles. Multiplexed analysis showed a 97% reduction in nonspecific protein adsorption for all polymer layers created. PMID:21773613

  12. Particle Generation by Ultraviolet-Laser Ablation during Surface Decontamination

    SciTech Connect

    Cheng, Mengdawn [ORNL

    2006-01-01

    A novel photonic decontamination method was developed by removal of pollutants from material surfaces. Such a method relies on the ability of a high-energy laser beam to ablate materials from a contaminated surface layer, thus producing airborne particles. In this paper, the authors presented the results obtained using a scanning mobility particle sizer (SMPS) system and an aerosol particle sizer (APS). Particles generated by laser ablation from the surfaces of cement, chromium-embedded cement, and alumina were experimentally investigated. Broad particle distributions from nanometer to micrometer in size were measured. For stainless steel, virtually no particle >500 nm in aerodynamic size was detected. The generated particle number concentrations of all three of the materials were increased as the 266-nm laser fluence (milijoules per square centimeter) increased. Among the three materals tested, cement was found to be the most favorable for particle removal, alumina next, and stainless steel the least. Chromium (dropped in cement) showed almost no effects on particle production. For all of the materials tested except for stainless steel, bimodal size distributions were observed; a smaller mode peaked at ~50-70 nm was detected by SMPS and a larger mode (peaked at ~0.70-0.85 m) by APS. Based on transmission electron microscopy observations, the authors concluded that particles in the range of 50-70 nm were aggregates of primary particles, and those of size larger than a few hundred nanometers were produced by different mechanisms, for example, massive object ejection from the material surfaces.

  13. Limiting diffusion current at rotating disk electrode with dense particle layer.

    PubMed

    Wero?ski, P; Nosek, M; Batys, P

    2013-09-28

    Exploiting the concept of diffusion permeability of multilayer gel membrane and porous multilayer we have derived a simple analytical equation for the limiting diffusion current at rotating disk electrode (RDE) covered by a thin layer with variable tortuosity and porosity, under the assumption of negligible convection in the porous film. The variation of limiting diffusion current with the porosity and tortuosity of the film can be described in terms of the equivalent thickness of stagnant solution layer, i.e., the average ratio of squared tortuosity to porosity. In case of monolayer of monodisperse spherical particles, the equivalent layer thickness is an algebraic function of the surface coverage. Thus, by means of cyclic voltammetry of RDE with a deposited particle monolayer we can determine the monolayer surface coverage. The effect of particle layer adsorbed on the surface of RDE increases non-linearly with surface coverage. We have tested our theoretical results experimentally by means of cyclic voltammetry measurements of limiting diffusion current at the glassy carbon RDE covered with a monolayer of 3 ?m silica particles. The theoretical and experimental results are in a good agreement at the surface coverage higher than 0.7. This result suggests that convection in a monolayer of 3 ?m monodisperse spherical particles is negligibly small, in the context of the coverage determination, in the range of very dense particle layers. PMID:24089793

  14. Modeled heating and surface erosion comparing motile (gas borne) and stationary (surface coating inert particle additives

    NASA Astrophysics Data System (ADS)

    Buckingham, A. C.; Siekhaus, W. J.

    1982-09-01

    The unsteady, non-similar, chemically reactive, turbulent boundary layer equations are modified for gas plus dispersed solid particle mixtures, for gas phase turbulent combustion reactions and for heterogeneous gas-solid surface erosive reactions. The exterior (ball istic core) edge boundary conditions for the solutions are modified to include dispersed particle influences on core propellant combustion-generated turbulence levels, combustion reactants and products, and reaction-induced, non-isentropic mixture states. The wall surface (in this study it is always steel) is considered either bare or coated with a fixed particle coating which is conceptually nonreactive, insulative, and nonablative. Two families of solutions are compared. These correspond to: (1) consideration of gas-borne, free-slip, almost spontaneously mobile (motile) solid particle additives which influence the turbulent heat transfer at the uncoated steel surface and, in contrast, (2) consideration of particle-free, gas phase turbulent heat transfer to the insulated surface coated by stationary particles.

  15. Characteristics of the Martian atmosphere surface layer

    NASA Technical Reports Server (NTRS)

    Clow, G. D.; Haberle, R. M.

    1990-01-01

    Elements of various terrestrial boundary layer models are extended to Mars in order to estimate sensible heat, latent heat, and momentum fluxes within the Martian atmospheric surface ('constant flux') layer. The atmospheric surface layer consists of an interfacial sublayer immediately adjacent to the ground and an overlying fully turbulent surface sublayer where wind-shear production of turbulence dominates buoyancy production. Within the interfacial sublayer, sensible and latent heat are transported by non-steady molecular diffusion into small-scale eddies which intermittently burst through this zone. Both the thickness of the interfacial sublayer and the characteristics of the turbulent eddies penetrating through it depend on whether airflow is aerodynamically smooth or aerodynamically rough, as determined by the Roughness Reynold's number. Within the overlying surface sublayer, similarity theory can be used to express the mean vertical windspeed, temperature, and water vapor profiles in terms of a single parameter, the Monin-Obukhov stability parameter. To estimate the molecular viscosity and thermal conductivity of a CO2-H2O gas mixture under Martian conditions, parameterizations were developed using data from the TPRC Data Series and the first-order Chapman-Cowling expressions; the required collision integrals were approximated using the Lenard-Jones potential. Parameterizations for specific heat and binary diffusivity were also determined. The Brutsart model for sensible and latent heat transport within the interfacial sublayer for both aerodynamically smooth and rough airflow was experimentally tested under similar conditions, validating its application to Martian conditions. For the surface sublayer, the definition of the Monin-Obukhov length was modified to properly account for the buoyancy forces arising from water vapor gradients in the Martian atmospheric boundary layer. It was found that under most Martian conditions, the interfacial and surface sublayers offer roughly comparable resistance to sensible heat and water vapor transport and are thus both important in determining the associated fluxes.

  16. Electronic structure of bacterial surface protein layers

    SciTech Connect

    Maslyuk, Volodymyr V.; Mertig, Ingrid; Bredow, Thomas; Mertig, Michael; Vyalikh, Denis V.; Molodtsov, Serguei L. [Martin-Luther-Universitaet Halle-Wittenberg, Fachbereich Physik, D-06099 Halle (Germany); Institut fuer Physikalische und Theoretische Chemie, Universitaet Bonn, D-53115 Bonn (Germany); Max-Bergmann-Zentrum fuer Biomaterialien, Technische Universitaet Dresden, D-01062 Dresden (Germany); Institut fuer Festkoerperphysik, Technische Universitaet Dresden, D-01062 Dresden (Germany)

    2008-01-15

    We report an approach for the calculation of the electronic density of states of the dried two-dimensional crystalline surface protein layer (S layer) of the bacterium Bacillus sphaericus NCTC 9602. The proposed model is based on the consideration of individual amino acids in the corresponding conformation of the peptide chain which additively contribute to the electronic structure of the entire protein complex. The derived results agree well with the experimental data obtained by means of photoemission (PE), resonant PE, and near-edge x-ray absorption spectroscopy.

  17. Using particles to sample and control implicit surfaces

    Microsoft Academic Search

    Andrew P. Witkin; Paul S. Heckbert

    2005-01-01

    We present a new particle-based approach to sampling and controlling implicit surfaces. A simple constraint locks a set of particles onto a surface while the particles and the surface move. We use the constraint to make surfaces follow particles, and to make particles follow surfaces. We implement control points for direct manipulation by specifying particle motions, then solving for surface

  18. Using particles to sample and control implicit surfaces

    Microsoft Academic Search

    Andrew P. Witkin; Paul S. Heckbert

    1994-01-01

    We present a new particle-based approach to sampling and controlling implicit surfaces. A simple constraint locks a set of particles onto a surface while the particles and the surface move. We use the constraint to make surfaces follow particles, and to make particles follow surfaces. We implement control points for direct manipulation by specifying particle motions, then solving for surface

  19. Inclined lidar observations of boundary layer aerosol particles above the Kongsfjord, Svalbard

    NASA Astrophysics Data System (ADS)

    Lampert, Astrid; Ström, Johan; Ritter, Christoph; Neuber, Roland; Yoon, Young; Chae, Nam; Shiobara, Masataka

    2012-10-01

    An inclined lidar with vertical resolution of 0.4 m was used for detailed boundary layer studies and to link observations at Zeppelin Mountain (474 m) and Ny-Ålesund, Svalbard. We report on the observation of aerosol layers directly above the Kongsfjord. On 29 April 2007, a layer of enhanced backscatter was observed in the lowest 25 m above the open water surface. The low depolarization ratio indicated spherical particles. In the afternoon, this layer disappeared. The ultrafine particle concentration at Zeppelin and Corbel station (close to the Kongsfjord) was low. On 1 May 2007, a drying process in the boundary layer was observed. In the morning, the atmosphere up to Zeppelin Mountain showed enhanced values of the backscatter coefficient. Around noon, the top of the highly reflecting boundary layer decreased from 350 to 250 m. The top of the boundary layer observed by lidar was confirmed by radiosonde data.

  20. All-nanoparticle layer-by-layer surface modification of micro- and ultrafiltration membranes.

    PubMed

    Escobar-Ferrand, Luis; Li, Diya; Lee, Daeyeon; Durning, Christopher J

    2014-05-20

    Layer-by-layer (LbL) deposition using primarily inorganic silica nanoparticles is employed for surface modification of polymeric micro- and ultrafiltration (MF/UF) membranes to produce novel thin film composite (TFC) membranes intended for nanofiltration (NF) and reverse osmosis (RO) applications. A wide variety of porous substrate membranes with different surface characteristics are successfully employed. This report gives detailed results for polycarbonate track etched (PCTE), polyethersulfone (PES), and sulfonated PES (SPEES) MF/UF substrates. Both spherical (cationic/anionic) and eccentric elongated (anionic) silica nanoparticles are deposited using conditions similar to those in prior works for solid substrates (e.g., Lee et al.). Appropriate selection of the pH for anionic and cationic particle deposition enables construction of nanoparticle-only layers 100-1200 nm in thickness atop the original porous membrane substrates. The surface layer thickness appears to vary linearly with the number of bilayers deposited, i.e., with the number of anionic/cationic deposition cycles. The deposition process is optimized to eliminate drying-induced cracking and improve mechanical durability via thickness control and postdeposition hydrothermal treatment. "Dead-end" permeation tests using dextran standards reveal the hydraulic characteristics and separations capability for the PCTE-based TFC membranes. The results show that nanoparticle-based LbL surface modification of MF and UF rated media can produce TFC membranes with NF capabilities. PMID:24568094

  1. Microthermal Instrument for Measuring Surface Layer Seeing

    NASA Astrophysics Data System (ADS)

    Li, Xue-Bao; Zheng, Yan-Fang; Deng, Lin Hua; Xu, Guang

    2012-02-01

    Microthermal fluctuations are introduced by atmospheric turbulence very near the ground. In order to detect microthermal fluctuations at Fuxian Solar Observatory (FSO), a microthermal instrument has been developed. The microthermal instrument consists of a microthermal sensor, which is based on a Wheatstone bridge circuit and uses fine tungsten filaments as resistance temperature detectors, an associated signal processing unit, and a data collection, & communication subsystem. In this paper, after a brief introduction to surface layer seeing, we discuss the instrumentation behind the microthermal detector we have developed and then present the results obtained. The results of the evaluation indicate that the effect of the turbulent surface boundary layer to astronomical seeing would become sufficiently small when installing a telescope at a height of 16m or higher from the ground at FSO.

  2. Surface modeling with oriented particle systems

    Microsoft Academic Search

    Richard Szeliski; David Tonnesen

    1992-01-01

    Splines and deformable surface models are widely used in computer graphics to describe free-form surfaces. These methods require manual preprocessing to discretize the surface into patches and to specify their connectivity. We present a new model of elastic sur- faces based on interacting particle systems, which, unlike previous techniques, can be used to sptiL join, or extend surfaces without the

  3. Reducing particle adhesion by material surface engineering

    NASA Astrophysics Data System (ADS)

    Crowder, Mark S.; Stover, Robert; Lawitzke, Anna; Devaud, Genevieve; Dove, Adrienne; Wang, Xu

    2010-08-01

    We have developed surface chemical modification processes which when applied to a variety of surfaces renders the surfaces resistant to particulate contamination. Chemically modified surfaces are shown to shed particles at a dramatically higher level as compared to native surfaces. This is demonstrated on a variety of surfaces that include optics, polymers, metals and silicon. The adhesive force between lunar stimulant particles (JSC-1AF) and black Kapton is measured to decrease by 95% when the black Kapton surface is chemically modified. The chemical modification process is demonstrated to not change the surface roughness of a smooth silicon wafer while decreasing particle affinity. The optical properties of chemically modified surfaces are reported. The surface modification process is robust and stable to aggressive cleaning. The particle shedding properties of chemically modified surfaces are retained after simulated extraterrestrial vacuum ultra-violet light exposure and temperature excursions to 140°C. This technology has the potential to provide a robust passive particle mitigation solution for optics, mechanical systems and particle sensitive applications.

  4. Improvement of Surface Layer Characteristics by Shot Lining

    NASA Astrophysics Data System (ADS)

    Harada, Yasunori

    In the present study, lining of the metal with foils using shot peening was investigated to improve the surface layer characteristics. In the shot peening experiment, the foils set on the metal are pelted with hard particles traveling at a high velocity. The foils are bonded to the metal surface due to plastic deformation induced by the collision of the particles. The foils and the metal are heated to heighten the bondability because of the reduction of flow stress. Lining the metal with the hard powder sandwiched between two aluminum foil sheets was also attempted. In this experiment, a centrifugal shot peening machine wite an electrical heater was employed. The metals are commercially aluminium alloys and magnesium alloys, and the foils are commercially aluminum, titanium and nickel. The effects of shot speed and the heating temperature on the bondability were examined. Wear resistance was also evaluated by grinding. The foils were successfully bonded to the metal surface. It was found that the present method is effective in improving of surface layer characteristics.

  5. Chalk-Ex—Fate of CaCO3 particles in the mixed layer: Evolution of patch optical properties

    Microsoft Academic Search

    W. M. Balch; A. J. Plueddeman; B. C. Bowler; D. T. Drapeau

    2009-01-01

    The fate of particles in the mixed layer is of great relevance to the global carbon cycle as well as to the propagation of light in the sea. We conducted four manipulative field experiments called “Chalk-Ex” in which known quantities of uniform, calcium carbonate particles were injected into the surface mixed layer. Since the production term for these patches was

  6. Surface heat transfer due to particle impact

    SciTech Connect

    Sun, J.; Chen, M.M.; Chao, B.T. (Illinois Univ., Urbana, IL (USA). Dept. of Mechanical and Industrial Engineering)

    1989-08-01

    In a fluidized bed of high gas velocities, particle impact on an immersed surface is an important mechanism for heat transfer. The heat exchange between an impacting spherical particle and surface is analyzed by considering (1) the heat conduction through the time varying contact area during the period when the particle is in contact with the surface, and (2) the heat conduction through the surrounding gas during the period when the particle is approaching and rebounding from the surface. For the solid conduction problem, an analytical solution is obtained for small Fourier numbers, and a correction factor is computed numerically to be used for large Fourier numbers. For the gas conduction problem, a solution is obtained by combining three analytical solutions each valid in a certain region of the gas domain. Since heat transfer due to the impact of a stream of falling particles was also measured with a simple experimental set up. 53 refs., 15 figs., 1 tab.

  7. Polymer surface treatment with particle beams

    DOEpatents

    Stinnett, Regan W. (1033 Tramway La. NE., Albuquerque, NM 87122); VanDevender, J. Pace (7604 Lamplighter NE., Albuquerque, NM 87109)

    1999-01-01

    A polymer surface and near surface treatment process produced by irradiation with high energy particle beams. The process is preferably implemented with pulsed ion beams. The process alters the chemical and mechanical properties of the polymer surface in a manner useful for a wide range of commercial applications.

  8. Are atmospheric surface layer flows ergodic?

    NASA Astrophysics Data System (ADS)

    Higgins, Chad W.; Katul, Gabriel G.; Froidevaux, Martin; Simeonov, Valentin; Parlange, Marc B.

    2013-06-01

    The transposition of atmospheric turbulence statistics from the time domain, as conventionally sampled in field experiments, is explained by the so-called ergodic hypothesis. In micrometeorology, this hypothesis assumes that the time average of a measured flow variable represents an ensemble of independent realizations from similar meteorological states and boundary conditions. That is, the averaging duration must be sufficiently long to include a large number of independent realizations of the sampled flow variable so as to represent the ensemble. While the validity of the ergodic hypothesis for turbulence has been confirmed in laboratory experiments, and numerical simulations for idealized conditions, evidence for its validity in the atmospheric surface layer (ASL), especially for nonideal conditions, continues to defy experimental efforts. There is some urgency to make progress on this problem given the proliferation of tall tower scalar concentration networks aimed at constraining climate models yet are impacted by nonideal conditions at the land surface. Recent advancements in water vapor concentration lidar measurements that simultaneously sample spatial and temporal series in the ASL are used to investigate the validity of the ergodic hypothesis for the first time. It is shown that ergodicity is valid in a strict sense above uniform surfaces away from abrupt surface transitions. Surprisingly, ergodicity may be used to infer the ensemble concentration statistics of a composite grass-lake system using only water vapor concentration measurements collected above the sharp transition delineating the lake from the grass surface.

  9. Creation of giant two-dimensional crystal of zinc oxide nanodisk by method of single-particle layer of organo-modified inorganic fine particles.

    PubMed

    Meng, Qi; Honda, Nanami; Uchida, Saki; Hashimoto, Kazuaki; Shibata, Hirobumi; Fujimori, Atsuhiro

    2015-09-01

    In this study, the formation and structure of a single-particle layer of organo-zinc oxide are investigated using surface-pressure-area (?-A) isotherms, out-of-plane X-ray diffraction (XRD) analysis, and atomic force microscopy (AFM). Further, techniques for achieving the solubilization of inorganic fine particles in general solvents have been proposed, and a single-particle layer has been formed using such an inorganic solution as a "spreading solution" for an interfacial film. Surface modification of ZnO is performed using a long-chain carboxylic acid. Accordingly, a regular arrangement of ZnO can be easily achieved in order to overcome the relatively weak van der Walls interactions between inorganic materials. A condensed Langmuir monolayer of these particles is also formed. A multiparticle layered structure is constructed by the Langmuir-Blodgett (LB) technique. Out-of-plane XRD measurement results for a single-particle layer of organo-ZnO clearly show a sharp peak at 42Å. This peak is attributed to the distance between ZnO layers. The AFM image of this single-particle layer of organo-ZnO shows a particle assembly with a uniform height of 60nm. These aggregated particles form large two-dimensional crystals. In other words, a regular periodic structure along the c-axis and a condensed single-particle layer had been fabricated using Langmuir and LB techniques. PMID:25978556

  10. Spontaneous dispersion of particles on liquid surfaces.

    PubMed

    Singh, Pushpendra; Joseph, Daniel D; Gurupatham, Sathish K; Dalal, Bhavin; Nudurupati, Sai

    2009-11-24

    When small particles (e.g., flour, pollen, etc.) come in contact with a liquid surface, they immediately disperse. The dispersion can occur so quickly that it appears explosive, especially for small particles on the surface of mobile liquids like water. This explosive dispersion is the consequence of capillary force pulling particles into the interface causing them to accelerate to a relatively large velocity. The maximum velocity increases with decreasing particle size; for nanometer-sized particles (e.g., viruses and proteins), the velocity on an air-water interface can be as large as approximately 47 m/s. We also show that particles oscillate at a relatively high frequency about their floating equilibrium before coming to stop under viscous drag. The observed dispersion is a result of strong repulsive hydrodynamic forces that arise because of these oscillations. PMID:19906995

  11. Electrorotation of colloidal particles and cells depends on surface charge.

    PubMed Central

    Maier, H

    1997-01-01

    The importance of surface conductivity to the frequency-dependent polarizability and the rotation of particles in circular electric fields (electrorotation) is emphasized by various theoretical and experimental investigations. Although surface conductivity seems to be naturally related to the ionic double layer, there is rare experimental evidence of a direct relationship. To highlight the role of surface charges in electrorotation, an apparatus was developed with a symmetrical three-electrode arrangement for field frequencies between 25 Hz and 80 MHz. The three-dimensional electrostatic field distribution between the electrodes was evaluated numerically. With this device, rotating, gradient, and homogeneous electric fields of defined precision and homogeneity could be applied to slightly conducting suspensions. Surface properties of monodisperse latex particles (O 9.67 microm), carrying weak acid groups, were characterized by suspension conductometric titration. This procedure determined the amount of carboxyl groups and showed that strong acid groups were missing on the surface of these particles. To obtain the electrophoretic mobility, the spheres were separated by free-flow electrophoresis, and the zeta-potential was calculated from these data. Single-particle rotation experiments on fractions of specified electrophoretic mobility were carried out at frequencies between 25 Hz and 20 MHz. By analyzing the pH dependence of the rotation velocity, it could be shown that the rotation rate is determined by surface charges, both at the peak in rotation rate near the Maxwell-Wagner frequency (MWF) and at low frequencies. The inversion of the rotation direction at the MWF peak for vanishing surface charges was demonstrated. An analytical model for the double layer and dissociation on a charged surface was developed that is valid for low and high zeta-potentials. This model could provide convincing evidence of the linear dependence of the MWF rotation velocity on surface charge. Images FIGURE 1 PMID:9284328

  12. Electrorotation of colloidal particles and cells depends on surface charge.

    PubMed

    Maier, H

    1997-09-01

    The importance of surface conductivity to the frequency-dependent polarizability and the rotation of particles in circular electric fields (electrorotation) is emphasized by various theoretical and experimental investigations. Although surface conductivity seems to be naturally related to the ionic double layer, there is rare experimental evidence of a direct relationship. To highlight the role of surface charges in electrorotation, an apparatus was developed with a symmetrical three-electrode arrangement for field frequencies between 25 Hz and 80 MHz. The three-dimensional electrostatic field distribution between the electrodes was evaluated numerically. With this device, rotating, gradient, and homogeneous electric fields of defined precision and homogeneity could be applied to slightly conducting suspensions. Surface properties of monodisperse latex particles (O 9.67 microm), carrying weak acid groups, were characterized by suspension conductometric titration. This procedure determined the amount of carboxyl groups and showed that strong acid groups were missing on the surface of these particles. To obtain the electrophoretic mobility, the spheres were separated by free-flow electrophoresis, and the zeta-potential was calculated from these data. Single-particle rotation experiments on fractions of specified electrophoretic mobility were carried out at frequencies between 25 Hz and 20 MHz. By analyzing the pH dependence of the rotation velocity, it could be shown that the rotation rate is determined by surface charges, both at the peak in rotation rate near the Maxwell-Wagner frequency (MWF) and at low frequencies. The inversion of the rotation direction at the MWF peak for vanishing surface charges was demonstrated. An analytical model for the double layer and dissociation on a charged surface was developed that is valid for low and high zeta-potentials. This model could provide convincing evidence of the linear dependence of the MWF rotation velocity on surface charge. PMID:9284328

  13. Thermal Fatigue Material Degradation of Caster Rolls' Surface Layers

    Microsoft Academic Search

    P. Yasniy; P. Maruschak; Y. Lapusta; V. Hlado; D. Baran

    2008-01-01

    Degradation of surface layers of continuous caster rolls under service conditions is studied. The roll material is steel 25 Kh1M1F. A statistical analysis of size, orientation and distribution of surface cracks is carried out. Microhardness measurements are performed and structural degradation of the material surface layers is evaluated as a function of the distance to the roll surface. It is

  14. Beta particle monitor for surfaces

    DOEpatents

    MacArthur, Duncan W. (Los Alamos, NM)

    1997-01-01

    A beta radiation detector which is capable of reliably detecting beta radiation emitted from a surface. An electrically conductive signal collector is adjustably mounted inside an electrically conductive enclosure which may define a single large opening for placing against a surface. The adjustable mounting of the electrically conductive signal collector can be based on the distance from the surface or on the expected beta energy range. A voltage source is connected to the signal collector through an electrometer or other display means for creating an electric field between the signal collector and the enclosure. Air ions created by the beta radiation are collected and the current produced is indicated on the electrometer or other display means.

  15. Texturing of layered surfaces for optimal viewing.

    PubMed

    Bair, Alethea S; House, Donald H; Ware, Colin

    2006-01-01

    This paper is a contribution to the literature on perceptually optimal visualizations of layered three-dimensional surfaces. Specifically, we develop guidelines for generating texture patterns, which, when tiled on two overlapped surfaces, minimize confusion in depth-discrimination and maximize the ability to localize distinct features. We design a parameterized texture space and explore this texture space using a "human in the loop" experimental approach. Subjects are asked to rate their ability to identify Gaussian bumps on both upper and lower surfaces of noisy terrain fields. Their ratings direct a genetic algorithm, which selectively searches the texture parameter space to find fruitful areas. Data collected from these experiments are analyzed to determine what combinations of parameters work well and to develop texture generation guidelines. Data analysis methods include ANOVA, linear discriminant analysis, decision trees, and parallel coordinates. To confirm the guidelines, we conduct a post-analysis experiment, where subjects rate textures following our guidelines against textures violating the guidelines. Across all subjects, textures following the guidelines consistently produce high rated textures on an absolute scale, and are rated higher than those that did not follow the guidelines. PMID:17080843

  16. Rebound characteristics for ash particles impacting a planar surface

    NASA Astrophysics Data System (ADS)

    Dong, Ming; Li, Sufen; Han, Jian; Xie, Jun

    2013-06-01

    The formation of ash deposition on the heat transfer tubes in a boiler reduces the heat transfer coefficient by about 25%. Because of these fouling layers, the efficiency with which energy can be absorbed from flue gases is reduced. The growth of ash deposition is strongly dependent on the interaction of the incident particle with the surface of heat transfer tubes. In this study the interaction is modeled as the outcome of collision between an incident fly ash particle and planar surface that represents a heat transfer surface. The present paper focuses on the applicability of the experimental results to indicate the rebound characteristics of fly ash particles impacting a planar surface. This is studied by impaction experiments of fly ash particles from the power plant dust, under various particle diameters and with different velocities (ranging from 0.1 to 20 m/s). The experiments are carried out in an atmospheric column, and using a digital camera system, individual impacts are recorded. Furthermore, the measured coefficient of restitution values can be predicted by a dynamic simulation model.

  17. Particle Levitation in a Plasma Sheath Above a Surface

    NASA Astrophysics Data System (ADS)

    Sickafoose, Amanda; Colwell, Josh; Horanyi, Mihaly; Robertson, Scott

    2001-10-01

    Dust grains suspended above the lunar surface have been observed on multiple occasions. Virtually all small, airless bodies in the solar system are coated with a dusty regolith; therefore, charged dust particle levitation and transport may also occur in planetary ring systems, on Mars, Mercury, planetary satellites, asteroids, and comets. The interaction between charged dust particles and a photoelectron layer or plasma sheath above the surface is the most likely explanation for these dust dynamics. We report the results of experiments on the levitation, dynamics, and charging of dust particles in an Ar plasma sheath above a flat plate. Types of particles tested include hollow and solid glass microballoons (<45 microns in diameter), polystyrene DVB beads (5 microns and 10 microns in diameter), and JSC-1, a lunar regolith simulant (<25 microns in diameter). Plasma and sheath characteristics are determined through Langmuir probe and floating potential probe sweeps. An agitator under the surface provides a disturbance to inject dust into the sheath. Dust particles levitating above the surface of the plate are illuminated by an Ar laser and observed by a video camera.

  18. The singularity in particle-laden boundary layers

    NASA Astrophysics Data System (ADS)

    Foster, M. R.; Duck, P. W.; Hewitt, R. E.

    2006-11-01

    The classical ``dusty gas'' equations have been used recently in a number of investigations by the authors to model boundary-layer flows of dilute suspensions of heavy particles. Though none of the difficulties of well-posedness that so often occur in more complicated particle-laden flow models seems to arise for this equation set, what does nearly always appear, and is now well documented in a variety of boundary layers, is a wall singularity that occurs at a finite distance from the leading edge, where the volume fraction is unbounded. The dusty-gas approximation replaces the quantity ``1-?'' everywhere in the particle-laden equations by ``1''. One is forced to seek a more complicated model in order to remove the unphysical singularity, and there are plenty of candidates--including particle pressure, added mass, particle-particle interactions. From the point of view of modifying the theory in the simplest possible way, we restore ``1-?'' where it had been replaced by ``1,'' and do nothing more. Such a procedure removes the singularity in boundary-layer flows, and we present computational and analytical results under such a change See, most recently, Foster, Duck & Hewitt (2006) Proc. Roy. Soc A 462, 1145

  19. Development of titanium oxide layer containing nanocrystalline zirconia particles with tetragonal structure: Structural and biological characteristics.

    PubMed

    Shin, Ki Ryong; Kim, Yeon Sung; Kim, Gye Won; Ko, Young Gun; Shin, Dong Hyuk

    2015-07-01

    This study investigated the microstructural, mechanical and biological properties of oxide layers containing tetragonal zirconia (t-ZrO2) particles on pure titanium produced by plasma electrolytic oxidation (PEO) process. For this purpose, PEO processes were carried out at an AC current density of 200mA/cm(2) for 180s in potassium pyrophosphate (K4P2O7) electrolytes with and without t-ZrO2 powder. Structural investigations using transmission electron microscopy exhibited that the present nanocrystalline oxide layer evidenced the successful incorporation of a myriad of t-ZrO2 particles working as an intermediate medium to reinforce the adhesion strength between the substrate and oxide layer. Regarding biomimetic apatite formation, the t-ZrO2 particles uniformly spread were of considerable importance in triggering the nucleation and growth of biomimetic apatite on the surface of the oxide layer immersed in a simulated body fluid solution. The growth and proliferation rates of the osteoblasts (MC3T3-E1) cultured on the oxide layer with t-ZrO2 particles were higher than that without t-ZrO2 particles due to the higher roughness providing the better sites for the filopodia extension and interlocking. PMID:25956745

  20. Modeled heating and surface erosion comparing motile (gas borne) and stationary (surface coating) inert particle additives

    SciTech Connect

    Buckingham, A.C.; Siekhaus, W.J.

    1982-09-27

    The unsteady, non-similar, chemically reactive, turbulent boundary layer equations are modified for gas plus dispersed solid particle mixtures, for gas phase turbulent combustion reactions and for heterogeneous gas-solid surface erosive reactions. The exterior (ballistic core) edge boundary conditions for the solutions are modified to include dispersed particle influences on core propellant combustion-generated turbulence levels, combustion reactants and products, and reaction-induced, non-isentropic mixture states. The wall surface (in this study it is always steel) is considered either bare or coated with a fixed particle coating which is conceptually non-reactive, insulative, and non-ablative. Two families of solutions are compared. These correspond to: (1) consideration of gas-borne, free-slip, almost spontaneously mobile (motile) solid particle additives which influence the turbulent heat transfer at the uncoated steel surface and, in contrast, (2) consideration of particle-free, gas phase turbulent heat transfer to the insulated surface coated by stationary particles. Significant differences in erosive heat transfer are found in comparing the two families of solutions over a substantial range of interior ballistic flow conditions. The most effective influences on reducing erosive heat transfer appear to favor mobile, gas-borne particle additives.

  1. Attraction between two similar particles in an electrolyte: effects of Stern layer absorption.

    PubMed

    Plouraboué, Franck; Chang, Hua-Chia

    2010-03-01

    When Debye length is comparable or larger than the distance between two identical particles, the overlapping among the particles double-layers can play an important role in their interactions. This paper presents a theoretical analysis of the interaction among two identical particles with overlapped double-layers. We particularly focus on the effect of a Stern electro static condition from linearization of the adsorption isotherm near the isoelectric (neutrality) point in order to capture how polyvalent ion condensation affect sand reverses the surface charge. The stationary potential problem is solved within the framework of an asymptotic lubrication approach for a mean-field Poisson-Boltzmann model. Both spherical and cylindrical particles are analyzed. The results are finally discussed in the context of Debye-Hückel (D-H) limit and beyond it. PMID:20209246

  2. Variability of surface layer hydrography in the tropical Pacific Ocean

    Microsoft Academic Search

    Kentaro Ando; Michael J. McPhaden

    1997-01-01

    The purpose of this study is to examine the variation of ocean surface layer hydrography on interannual timescales in the tropical Pacific Ocean using conductivity-temperature-depth measurements from 1976 to 1994. We demonstrate that associated with interannual variations in atmospheric forcing, there were distinct changes in mixed layer temperature, salinity, depth, and barrier layer thickness between normal, El Niño, and La

  3. PARTICLE MOTION ON MAGNETIC FLUX SURFACES IN \\

    Microsoft Academic Search

    S. A. Colgate; H. P. Furth; C. W. Hartman; R. L. Spoerlein

    1961-01-01

    The stability and particle confinement properties of axial-field-; centered and hard-core linear pinches are studied. A weak, externally produced ; electron beam is passed along the pinch discharge, in order to determine the ; timevarying properties of the magnetic surfaces of various pinch configurations. ; Analysis of the emerging electron beam demonstrates the effects of turbulence on ; diffusion and

  4. Superhydrophobic surfaces via electroless displacement of nanometric Cu layers by Ag +

    NASA Astrophysics Data System (ADS)

    Brenier, R.; Ramos, S. M. M.; Montchanin, M.

    2009-05-01

    This paper explores the possibility of making hydrophobic and superhydrophobic surfaces from electroless displacement of Cu by Ag +, in the case where Cu oxidation is limited owing to Cu layers of nanometric thicknesses. The morphology of the Ag layers is studied by scanning electron microscopy for Cu thicknesses between 10 and 80 nm. The mapping of the elemental content of the layers by electron dispersive X-ray analysis also has been used to clarify the particle growing by diffusion limited aggregation. It is shown that the average size and the shape complexity of the Ag particles increase with the Cu thickness. The addition of dimethyl sulfoxide in the Ag + aqueous solution improves the surface homogeneity, increases the particle density and decreases their sizes. The wetting behaviour of the surfaces, after grafting with octadecanethiol, has been studied from measurements of the contact angles of a drop of water. According to the thickness of the initial Cu layer and the morphology of the Ag layer, contact angles range between 110° and 154°. Superhydrophobic surfaces are obtained from 80 nm thick Cu layers.

  5. Aspects Of The Atmospheric Surface Layers On Mars And Earth

    Microsoft Academic Search

    S. E. Larsen; H. E. Jørgensen; L. Landberg; J. E. Tillman

    2002-01-01

    The structures of mean flow and turbulence in the atmospheric surface boundary layer have been extensively studied on Earth, and to a far less extent on Mars, where only the Viking missions and the Pathfinder mission have delivered in-situ data. Largely the behaviour of surface-layer turbulence and mean flow on Mars is found to obey the same scaling laws as

  6. Super-hydrophobic surfaces of layer-by-layer structured film-coated electrospun nanofibrous membranes

    Microsoft Academic Search

    Tasuku Ogawa; Bin Ding; Yuji Sone; Seimei Shiratori

    2007-01-01

    We have recently fabricated super-hydrophobic membrane surfaces based on the inspiration of self-cleaning silver ragwort leaves. This biomimetic super-hydrophobic surface was composed of fluoroalkylsilane (FAS)-modified layer-by-layer (LBL) structured film-coated electrospun nanofibrous membranes. The rough fibre surface caused by the electrostatic LBL coating of TiO2 nanoparticles and poly(acrylic acid) (PAA) was used to imitate the rough surface of nanosized grooves along

  7. Small particle transport across turbulent nonisothermal boundary layers

    NASA Technical Reports Server (NTRS)

    Rosner, D. E.; Fernandez De La Mora, J.

    1982-01-01

    The interaction between turbulent diffusion, Brownian diffusion, and particle thermophoresis in the limit of vanishing particle inertial effects is quantitatively modeled for applications in gas turbines. The model is initiated with consideration of the particle phase mass conservation equation for a two-dimensional boundary layer, including the thermophoretic flux term directed toward the cold wall. A formalism of a turbulent flow near a flat plate in a heat transfer problem is adopted, and variable property effects are neglected. Attention is given to the limit of very large Schmidt numbers and the particle concentration depletion outside of the Brownian sublayer. It is concluded that, in the parameter range of interest, thermophoresis augments the high Schmidt number mass-transfer coefficient by a factor equal to the product of the outer sink and the thermophoretic suction.

  8. Airborne Measured New Particle Formation Event in the Atmospheric Boundary Layer

    NASA Astrophysics Data System (ADS)

    Platis, Andreas; Altstädter, Barbara; Wehner, Birgit; Wildmann, Norman; Lampert, Astrid; Hermann, Markus; Bange, Jens

    2015-04-01

    A new particle formation (NPF) event measured by unmanned aerial systems is presented. The NPF occurred during the morning transition of the atmospheric boundary-layer near Melpitz, Germany, during springtime. Airborne measurements were able to capture the morning transition continuously from a shallow convective boundary layer below a strong capping inversion layer to a mixed boundary layer with high temporal and spatial resolution of thermodynamics, turbulence and nucleation mode particles number concentrations. Airborne measured vertical profiles from the surface up to 1000 m show the start of a NPF event with enhanced concentrations of nucleation mode particles within the thermal inversion. We show that the inversion layer was responsible for creating favorable thermodynamic conditions for a NPF. Strong gradients of mean potential temperature and mixing ratio, as well as a 10 times higher temperature structure parameter CT2 and 5 times higher humidity structure parameter CQ2 than in the remaining parts of the vertical profile were observed in the inversion. Only high turbulent fluctuations of temperature and humidity plus relatively high dissipation rates create the conditions for supersaturation of precursor gases due to non-linear mixing. Further an anti-correlation of temperature and humidity fluctuations is observed in the layer, where new particle formation is assumed. Our observations support the hypothesis that NPF is likely to be initiated by the thermodynamics and turbulence of the inversion. With the estimation of turbulent mixing and dissipation rates we could prove that the downward transport of particles by convective eddies is the cause of the sudden increase of nucleation mode particles in ground data. Thus, it is very likely that these particles observed at the ground were formed locally at higher altitudes and mixed downwards. These observations have consequences for the interpretation of many earlier published ground-based observations of new NPF. In the morning, stable thermal stratification may trap enhanced concentrations of nucleation mode particles. Once daytime convection initiates, turbulence mixes the boundary layer, and the vertical profile of nucleation mode particles becomes more homogeneous. Without the airborne in-situ measurements, the observations at ground level could lead to a misinterpretation of location and processes causing the increase in nucleation mode particles.

  9. Surface plasma source with anode layer plasma accelerator

    SciTech Connect

    Dudnikov, Vadim [Muons, Inc., Batavia, Illinois 60510 (United States)

    2012-02-15

    Proposed plasma generation system can be used for high current negative ion beam production and for directed deposition by flux of sputtered neutrals and negative ions. The main mechanism of negative ion formation in surface plasma sources is the secondary emission from low work function surface bombarded by a flux of positive ion or neutrals. The emission of negative ions is enhanced significantly by introducing a small amount of cesium or other substance with low ionization potential. In the proposed source are used positive ions generated by Hall drift plasma accelerator (anode layer plasma accelerator or plasma accelerator with insulated channel, with cylindrical or race track configuration of emission slit). The target-emitter is bombarded by the ion beam accelerated in crossed ExB fields. Negative ions are extracted from the target surface with geometrical focusing and are accelerated by negative voltage applied between emitter and plasma, contacting with the plasma accelerator. Hall drift ion source has a special design with a space for passing of the emitted negative ions and sputtered particles through the positive ion source.

  10. Formation of nanocrystalline surface layers in various metallic materials by near surface severe plastic deformation

    Microsoft Academic Search

    Masahide Sato; Nobuhiro Tsuji; Yoritoshi Minamino; Yuichiro Koizumi

    2004-01-01

    The surface of the various kinds of metallic materials sheets were severely deformed by wire-brushing at ambient temperature to achieve nanocrystalline surface layer. The surface layers of the metallic materials developed by the near surface severe plastic deformation (NS-SPD) were characterized by means of TEM. Nearly equiaxed nanocrystals with grain sizes ranging from 30 to 200 nm were observed in

  11. Surface Particle Detectors in Space Weather forecast

    NASA Astrophysics Data System (ADS)

    Chilingarian, Ashot

    Recently several groups report on the development of the alarm system based on the surface particle detector data. Among them are high-latitude neutron monitors network "Spaceship Earth", coordinated by the group from Bartol Research Center; Muon network coordinated by the group from Shinshu University and Athens Neutron Monitor Data Processing Center. In the presented report, based on the information content of data from particle detectors of Aragats Space Environmental Center (ASEC) we made attempt to review possibility of surface particle detectors in Space Weather forecasts. Particle monitors located at ASEC at 1000, 2000 and 3200 m altitudes (40?25 N, 44?15 E; Vertical cut-off rigidity in 2007: 7.1 GV) detect charged and neutral components of the secondary cosmic rays with different energy thresholds and various angles of incidence. ASEC monitors reliably detect the highest energy CR due to unique geographical location and large underground high energy muon detector. Forecasting of the Solar Energetic Proton (SEP) events by surface particle detectors is based on the detection of the Ground Level Enhancements (GLE). Unfortunately not all SEPs contain particles energetic enough to produce GLE, therefore, the efficiency of the warnings will not be very high. Nonetheless, we can expect that the major events, (like 1859, 1956, 1972, 1989) with high probability will generate GLEs and surface detectors can provide forewarnings on upcoming abundant SEP particles. With the exception of the event on 20 January, when due to very good magnetic connection of the flare site with earth, all relativistic particles seem to come simultaneously, the enhancements of GeV solar particles detected by surface particle detectors can alert on upcoming severe radiation storm. The alerts from middle and low latitude monitors are even more important compared to high latitude networks, because of lower probability of false alarms. If an enhancement occurs at monitors with large cutoff rigidity it indicates that spectral knee occurs at large enough energy. Enhancements in the ASEC detectors count rates indicate higher solar ion energies, and, consequently hard spectra of the GLE in progress. The triggers of the Geomagnetic Storms are huge magnetized clouds (Coronal mass ejections - CMEs), emitted by sun and traveling in the Interplanetary Space (IP). This gigantic plasma clouds with "frozen" magnetic field (Interplanetary CMEs, - ICMEs) disturb the Interplanetary Magnetic Field and "modulate "the ambient flux of the Galactic Cosmic rays (GCR). On the way to Earth (15 - 70 hours) the magnetic cloud and shock change GCR intensity and make it anisotropic. The strength of these modulation effects correlate with severity of the geomagnetic storm. Networks of the particle detectors located on Earth surface detect these modulation effects and can predict the upcoming geomagnetic storms hours before the ICME arrival at the magnetometers on ACE and SOHO space stations. We will demonstrate that simultaneously detection of the charged and neutral components of the secondary cosmic rays made by ASEC monitors enlarged possibilities of physical inference on the solar modulation effects and, therefore, enlarges possibilities of timely and reliable forecasts of dangerous consequences of radiation and geomagnetic storms.

  12. Generation and characterization of surface layers on acoustically levitated drops

    Microsoft Academic Search

    Rudolf Tuckermann; Sigurd Bauerecker; Heiko K. Cammenga

    2007-01-01

    Surface layers of natural and technical amphiphiles, e.g., octadecanol, stearic acid and related compounds as well as perfluorinated fatty alcohols (PFA), have been investigated on the surface of acoustically levitated drops. In contrast to Langmuir troughs, traditionally used in the research of surface layers at the air–water interface, acoustic levitation offers the advantages of a minimized and contact-less technique. Although

  13. Characterization and use of crystalline bacterial cell surface layers

    NASA Astrophysics Data System (ADS)

    Sleytr, Uwe B.; Sára, Margit; Pum, Dietmar; Schuster, Bernhard

    2001-10-01

    Crystalline bacterial cell surface layers (S-layers) are one of the most common outermost cell envelope components of prokaryotic organisms (archaea and bacteria). S-layers are monomolecular arrays composed of a single protein or glycoprotein species and represent the simplest biological membranes developed during evolution. S-layers as the most abundant of prokaryotic cellular proteins are appealing model systems for studying the structure, synthesis, genetics, assembly and function of proteinaceous supramolecular structures. The wealth of information existing on the general principle of S-layers have revealed a broad application potential. The most relevant features exploited in applied S-layer research are: (i) pores passing through S-layers show identical size and morphology and are in the range of ultrafiltration membranes; (ii) functional groups on the surface and in the pores are aligned in well-defined positions and orientations and accessible for chemical modifications and binding functional molecules in very precise fashion; (iii) isolated S-layer subunits from a variety of organisms are capable of recrystallizing as closed monolayers onto solid supports (e.g., metals, polymers, silicon wafers) at the air-water interface, on lipid films or onto the surface of liposomes; (iv) functional domains can be incorporated in S-layer proteins by genetic engineering. Thus, S-layer technologies particularly provide new approaches for biotechnology, biomimetics, molecular nanotechnology, nanopatterning of surfaces and formation of ordered arrays of metal clusters or nanoparticles as required for nanoelectronics.

  14. Interactions of hyaluronan layers with similarly charged surfaces: the effect of divalent cations.

    PubMed

    Jiang, Lei; Titmuss, Simon; Klein, Jacob

    2013-10-01

    We used colloidal probe atomic force microscopy to measure the normal forces between the surface of a silica colloidal particle and a sparse layer of hyaluronan (hyaluronic acid, HA, MW ? 10(6) Da) covalently attached to a planar silica surface, both across pure water and following the addition of 1 mM MgCl2. It was found that in the absence of salt the HA layer repelled the colloidal silica surface during both approach and retraction. The addition of the MgCl2, however, changes the net force between the negatively charged HA layer and the opposing negatively charged silica surface from repulsion to adhesion. This interaction reversal is attributed to the bridging effect of the added Mg(2+) ions. Our results provide first direct force data to support earlier simulation and predictions that such divalent cations could bridge between negative charges on opposing surfaces, leading to an overall reversal of force from repulsion to attraction. PMID:24011082

  15. Computer simulations of particle-surface dynamics

    SciTech Connect

    Karo, A.M.; Hiskes, J.R.; DeBoni, T.M.

    1986-10-01

    Our simulations of particle-surface dynamics use the molecular dynamics codes that we have developed over the past several years. The initial state of a molecule and the parameters defining the incoming trajectory can be specifically described or randomly selected. Statistical analyses of the states of the particles and their trajectories following wall collisions are carried out by the code. We have carried out calculations at high center-of-mass energies and low incidence angles and have examined the survival fraction of molecules and the dependence upon the incoming trajectory. We report also on preliminary efforts that are being made to simulate sputtering and recombinant desorption processes, since the recombinant desorption of hydrogen from typical wall materials may be an important source for vibrationally-excited hydrogen in volume sources; for surface sources the presence of occluded hydrogen may affect the concentration of atomic species.

  16. Surface cracking in layers under biaxial, residual compressive stress

    Microsoft Academic Search

    S. Ho; C. Hillman; F. F. Lange; Z. Suo

    1995-01-01

    Thin two-phase, AlâOâ\\/t-Zr(3Y)Oâ layers bounded by much thicker Zr(3Y)Oâ layers were fabricated by co-sintering powders. After cooling, cracks were observed along the center of the two-phase, AlâOâ\\/t-Zr(3Y)Oâ layers. Although the AlâOâ\\/t-Zr(3Y)Oâ layers are under residual, biaxial compression far from the surface, tensile stresses, normal to the center line, exist at and near the surface. These highly localized tensile stresses can

  17. Generation and characterization of surface layers on acoustically levitated drops.

    PubMed

    Tuckermann, Rudolf; Bauerecker, Sigurd; Cammenga, Heiko K

    2007-06-15

    Surface layers of natural and technical amphiphiles, e.g., octadecanol, stearic acid and related compounds as well as perfluorinated fatty alcohols (PFA), have been investigated on the surface of acoustically levitated drops. In contrast to Langmuir troughs, traditionally used in the research of surface layers at the air-water interface, acoustic levitation offers the advantages of a minimized and contact-less technique. Although the film pressure cannot be directly adjusted on acoustically levitated drops, it runs through a wide pressure range due to the shrinking surface of an evaporating drop. During this process, different states of the generated surface layer have been identified, in particular the phase transition from the gaseous or liquid-expanded to the liquid-condensed state of surface layers of octadecanol and other related amphiphiles. Characteristic parameters, such as the relative permeation resistance and the area per molecule in a condensed surface layer, have been quantified and were found comparable to results obtained from surface layers generated on Langmuir troughs. PMID:17376468

  18. Fluorescent particle tracers for surface hydrology

    NASA Astrophysics Data System (ADS)

    Tauro, F.; Grimaldi, S.; Rapiti, E.; Porfiri, M.

    2012-12-01

    Accurate estimates of flow velocity in natural environments are essential for the understanding of runoff and overland flow formation, rill development, erosion, and infiltration and evaporation mechanisms. Tracing technologies are generally considered valuable tools to estimate flow velocity in small watershed streams and shallow water flows. In this framework, a novel tracing methodology based on the deployment and observation of enhanced fluorescence particles for surface flow measurements is proposed. This approach aims at mitigating practical limitations of traditional techniques for monitoring stream and overland flows. Specifically, the insolubility of the particles minimizes tracer adhesion to natural substrates and, therefore, is expected to reduce the requisite quantity of tracing material as compared to liquid dyes. Further, the enhanced visibility of the fluorescent particles allows for non-intrusively detecting the tracer through imaging techniques without deploying bulky probes and samplers in the water. These features along with the use of basic and resilient equipment provide grounding for applying the proposed methodology in ephemeral micro-channels, high-sediment load flows, and heavy floods. The feasibility of the methodology is studied by conducting characterization analysis in laboratory settings and proof-of-concept experiments in natural environments. In addition, image analysis techniques are developed to automatically and noninvasively detect and trace the trajectory of the particles on surface flows. Experiments are performed in a natural mountainous river to assess the performance of the particles in stream flow settings, where high velocity regimes, presence of foam, and light reflections pose serious challenges to bead detection. Particles are used to conduct flow measurements at a stream cross-section and travel time experiments in stream reaches of up to 30 m. Bead diameters of a few millimeters are selected to compensate for high flow rates. Experimental results demonstrate that the fluorescent particles can be used to reliably trace high velocity streams in adverse illumination conditions and in the presence of foam and reflections on the water surface. Furthermore, flow velocities and travel times calculated through an array of commonly used tracers are consistent with results obtained through the proposed methodology and demonstrate a higher reliability of the fluorescent particles versus traditional tracers that are affected by dispersions and turbulence. Additional proof-of-concept experiments are conducted on a semi-natural hillslope plot under high turbidity loads and soil and rain drops interaction. Ad-hoc experiments with particles of varying diameters ranging from 75 to 1180 ?m are performed to assess the visibility and detectability of the particle tracers in these severe environmental conditions and their feasibility in estimating overland flow velocities. Videos of beads' transit are processed through both supervised and unsupervised techniques to obtain average surface velocities of water flowing on the hill. Experimental results have demonstrated the feasibility of using the particles for environmental applications and have led to the identification of optimal diameters, namely, 1000-1180 ?m, for flow measurements in the described hillslope plot.

  19. Layer silicates in a chondritic porous interplanetary dust particle

    NASA Technical Reports Server (NTRS)

    Rietmeijer, F. J. M.; Mackinnon, I. D. R.

    1985-01-01

    Analytical electron microscopy on individual grains from a portion of a chondritic porous interplanetary dust particle (aggregate W7029C1 from the NASA Johnson Space Center Cosmic Dust Collection) shows that layer silicates compose 50 percent of the silicate fraction examined. These layer silicates can be classified into two distinct crystallochemical groups: (1) fine-grained, polycrystalline smectite minerals; and (2) well-ordered, single crystals of kaolinite and Mg-poor talc. The layer silicates in this portion of sample W7029(asterisk)A are dissimilar to those described in other chondritic porous aggregates. The predominant layer silicate assemblage in W7029(asterisk)A indicates that heating of the aggregate during atmospheric entry was brief and probably to a temperature less than 300 C. Comparison with terrestrial phyllosilicate occurrences suggests that some layer silicates in aggregate W7029(asterisk)A may have been formed by alteratiton from preexisting silicate minerals at low temperatures (less than 25 C) after aggregate formation.

  20. On the effect of induced electro-osmosis on a cylindrical particle next to a surface.

    PubMed

    Zhao, Hui; Bau, Haim H

    2007-03-27

    The effect of induced electro-osmosis on a cylindrical particle positioned next to a planar surface (wall) is studied theoretically both under the thin double layer approximation utilizing the Smoluchowski slip velocity approximation and under thick electric double layer conditions by solving the Poisson-Nernst-Planck (PNP) equations. The imposed, undisturbed electric field is parallel to the planar surface. The induced hydrodynamic and electrostatic forces are calculated as functions of the particle's and the medium's dielectric constants and the distance between the particle and the surface. The resultant force acting on the particle is directed normal to and away from the wall. The presence of such a repulsive force may adversely affect the interactions between macromolecules suspended in solution and wall-immobilized molecules and may be significant to near-wall particle imaging velocimetry (PIV) in electrokinetic flows. PMID:17311434

  1. Particle Swarm Transport through Immiscible Fluid Layers in a Fracture

    NASA Astrophysics Data System (ADS)

    Teasdale, N. D.; Boomsma, E.; Pyrak-Nolte, L. J.

    2011-12-01

    Immiscible fluids occur either naturally (e.g. oil & water) or from anthropogenic processes (e.g. liquid CO2 & water) in the subsurface and complicate the transport of natural or engineered micro- or nano-scale particles. In this study, we examined the effect of immiscible fluids on the formation and evolution of particle swarms in a fracture. A particle swarm is a collection of colloidal-size particles in a dilute suspension that exhibits cohesive behavior. Swarms fall under gravity with a velocity that is greater than the settling velocity of a single particle. Thus a particle swarm of colloidal contaminants can potentially travel farther and faster in a fracture than expected for a dispersion or emulsion of colloidal particles. We investigated the formation, evolution, and break-up of colloidal swarms under gravity in a uniform aperture fracture as hydrophobic/hydrophyllic particle swarms move across an oil-water interface. A uniform aperture fracture was fabricated from two transparent acrylic rectangular prisms (100 mm x 50 mm x 100 mm) that are separated by 1, 2.5, 5, 10 or 50 mm. The fracture was placed, vertically, inside a glass tank containing a layer of pure silicone oil (polydimethylsiloxane) on distilled water. Along the length of the fracture, 30 mm was filled with oil and 70 mm with water. Experiments were conducted using silicone oils with viscosities of 5, 10, 100, or 1000 cSt. Particle swarms (5 ?l) were comprised of a 1% concentration (by mass) of 25 micron glass beads (hydrophilic) suspended in a water drop, or a 1% concentration (by mass) of 3 micron polystyrene fluorescent beads (hydrophobic) suspended in a water drop. The swarm behavior was imaged using an optical fluorescent imaging system composed of a CCD camera and by green (525 nm) LED arrays for illumination. Swarms were spherical and remained coherent as they fell through the oil because of the immiscibility of oil and water. However, as a swarm approached the oil-water interface, it decreased in speed and came to rest on the interface while maintaining its spherical shape. After the interface between a swarm and the oil thinned sufficiently, the swarm was rapidly released into the water layer. The time that this took depended on the viscosity of the oil layer, which determines the rate of thinning, and on the size and properties of the particles. The swarm geometry and velocity in the water layer depended on the aperture of the fracture, the viscosity of the oil and the hydrophobicity or hydrophyllicity of the particles in the swarm. Hydrophobic beads result in multiple mini swarms after breaking through the interface rather than a single large swarm like that observed for hydrophilic swarms. After many experiments a pile formed at the bottom of the tank near the center of the fracture, indicating that swarms can lead to locally high concentration of colloidal contaminants. Acknowledgment: The authors wish to acknowledge support of this work by the Geosciences Research Program, Office of Basic Energy Sciences US Department of Energy (DE-FG02-09ER16022) and the Summer Undergraduate Research Fellowship program at Purdue University.

  2. Surface nanostructure formation mechanism of 45 steel induced by supersonic fine particles pombarding

    Microsoft Academic Search

    Dema Ba; Shining Ma; Changqing Li; Fanjun Meng

    2008-01-01

    By means of supersonic fine particles bombarding (SFPB), a nanostructured surface layer up to 15 ?m was fabricated on a 45 steel plate with ferrite and pearlite phases. To reveal the grain refinement mechanism of SFPB-treated 45 steel, microstructure features of various sections in the treated surface were systematically characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission

  3. Hydraulic fracturing pressures in permeable surface layers

    Microsoft Academic Search

    Hagoort

    1978-01-01

    A theoretical analysis is presented of hydraulic fracturing pressures in permeable subsurface layers situated in a tectonically relaxed area. The analysis is based on the theory of linear poro-elasticity. Three different fracturing pressures can be distinguished: (1) fracture initiation pressure: the pressure in the borehole needed to part undamaged rock around the borehole; (2) fracture opening\\/closing pressure: the pressure in

  4. Surface Science Letters Surface electron accumulation in indium nitride layers grown

    E-print Network

    Dietz, Nikolaus

    Surface Science Letters Surface electron accumulation in indium nitride layers grown by high­H ter- mination with no indium overlayer or droplets and indicate that the layer is N-polar. Broad accumulation. These results indi- cate that surface electron accumulation on InN does not require excess indium

  5. Structure of the regular surface layer of Sporosarcina ureae.

    PubMed Central

    Stewart, M; Beveridge, T J

    1980-01-01

    Optical diffraction and computer image processing of electron micrographs were employed to analyze the structure of the regular surface layer of Sporosarcina ureae at high resolution. Negatively stained preparations of regular surface layer fragments showed two types of tetragonal pattern, each having p4 symmetry in projection with a = 12.8 nm. Although the two patterns differed greatly in overall appearance, both had a common pattern of areas of high stain density which we interpret as arising from gaps or holes in the structure. We speculate that these holes may be related to a protective role of the regular surface layer, whereby hostile environmental agents (such as muramidases) larger than about 2 nm would be screened from the underlying layers of the bacterial surface, while the free passage of nutrients and waste products into and out of the cell would still be allowed. Images PMID:7372574

  6. Effect of silica particle surface chemistry on the shear thickening behaviour of concentrated colloidal suspensions

    NASA Astrophysics Data System (ADS)

    Chu, Baojin; Brady, Andrew T.; Mannhalter, Bert D.; Salem, David R.

    2014-08-01

    We have found that heat treating silica particles can have a large effect on the shear thickening properties of suspensions comprised of 550 nm silica particles in ethylene glycol (EG). The shear thickening effect becomes stronger after heat treating the particles at the temperatures studied (120 and 220 °C) especially at the higher temperature, indicating that the interparticle interactions in these suspensions are changed by heat treatment. Having confirmed the existence of hydroxyl groups on the surface of the silica particles using differential scanning calorimetry, x-ray photoelectron spectroscopy showed that heat treatment increases the valence of the Si element on the surface, resulting in a higher density of hydroxyl groups. We believe that a denser solvation layer on the surface of heat-treated particles, formed by adsorbing EG molecules to the particle surface through hydrogen bonds between EG and hydroxyl groups, results in a higher short-range repulsive force, which is responsible for the enhanced shear thickening behaviour.

  7. Estimating Active Layer Thickness from Remotely Sensed Surface Deformation

    Microsoft Academic Search

    L. Liu; K. M. Schaefer; T. Zhang; J. M. Wahr

    2010-01-01

    We estimate active layer thickness (ALT) from remotely sensed surface subsidence during thawing seasons derived from interferometric synthetic aperture radar (InSAR) measurements. Ground ice takes up more volume than ground water, so as the soil thaws in summer and the active layer deepens, the ground subsides. The volume of melted ground water during the summer thaw determines seasonal subsidence. ALT

  8. Buffer Layer Assisted Laser Patterning of Metals on Surfaces

    E-print Network

    Asscher, Micha

    , variable width metallic wires. By employing laser desorption of a physisorbed buffer gas, a grating of goldBuffer Layer Assisted Laser Patterning of Metals on Surfaces Gabriel Kerner and Micha Asscher controlled metallic clusters via buffer layer assisted growth (BLAG).9-11 To create clusters, the metal

  9. Energetic Particle Synthesis of Metastable Layers for Superior Mechanical Properties

    SciTech Connect

    Follstaedt, D.M.; Knapp, J.A.; Myers, S.M.; Dugger, M.T.; Friedmann, T.A.; Sullivan, J.P. [Sandia National Labs., Albuquerque, NM (United States); Monteiro, O.R.; Ager, J.W. III; Brown, I.G.; Christenson, T. [Lawrence Berkeley National Lab., CA (United States)

    1998-01-01

    Energetic particle methods have been used to synthesize two metastable layers with superior mechanical properties: amorphous Ni implanted with overlapping Ti and C, and amorphous diamond-like carbon (DLC) formed by vacuum-arc deposition or pulsed laser deposition. Elastic modulus, yield stress and hardness were reliably determined for both materials by fitting finite-element simulations to the observed layer/substrate responses during nanoindentation. Both materials show exceptional properties, i.e., the yield stress of amorphous Ni(Ti,C) exceeds that of hardened steels and other metallic glasses, and the hardness of DLC (up to 88 GPa) approaches that of crystalline diamond (approx. 100 GPa). Tribological performance of the layers during unlubricated sliding contact appears favorable for treating Ni-based micro-electromechanical systems: stick-slip adhesion to Ni is eliminated, giving a low coefficient of friction (approx. 0.3-0.2) and greatly reduced wear. We discuss how energetic particle synthesis is critical to forming these phases and manipulating their properties for optimum performance.

  10. Inertial particles in a shearless mixing layer: direct numerical simulations

    NASA Astrophysics Data System (ADS)

    Ireland, Peter; Collins, Lance

    2010-11-01

    Entrainment, the drawing in of external fluid by a turbulent flow, is present in nearly all turbulent processes, from exhaust plumes to oceanic thermoclines to cumulus clouds. While the entrainment of fluid and of passive scalars in turbulent flows has been studied extensively, comparatively little research has been undertaken on inertial particle entrainment. We explore entrainment of inertial particles in a shearless mixing layer across a turbulent-non-turbulent interface (TNI) and a turbulent-turbulent interface (TTI) through direct numerical simulation (DNS). Particles are initially placed on one side of the interface and are advanced in time in decaying turbulence. Our results show that the TTI is more efficient in mixing droplets than the TNI. We also find that without the influence of gravity, over the range of Stokes numbers present in cumulus clouds, particle concentration statistics are essentially independent of the dissipation scale Stokes number. The DNS data agrees with results from experiments performed in a wind tunnel with close parametric overlap. We anticipate that a better understanding of the role of gravity and turbulence in inertial particle entrainment will lead to improved cloud evolution predictions and more accurate climate models. Sponsored by the U.S. NSF.

  11. Surface reactions on thin layers of silane coupling agents

    Microsoft Academic Search

    Dirk G. Kurth; Thomas Bein

    1993-01-01

    The reactivity of immobilized functional groups in thin layers of (3-aminopropyl)triethoxysilane (APS), (3-mercaptopropyl)trimethoxysilane, (3-bromopropyl)trimethoxysilane, and (8-bromooctyl)trimethoxysilane on oxidized aluminum substrates was studied with reflection-adsorption infrared spectroscopy (RAIR), optical ellipsometry and contact-angle measurements. Mass changes on the surface associated with the surface-confined reactions were measured with the quartz crystal microbalance (QCM). Single layers of (3-aminopropyl)triethoxysilane on oxidized aluminum react with chlorodimethylsilane

  12. A Lagrangian Stochastic Model for Heavy Particle Dispersion in the Atmospheric Marine Boundary Layer

    NASA Astrophysics Data System (ADS)

    Mueller, James A.; Veron, Fabrice

    2009-02-01

    The dispersion of heavy particles and pollutants is often simulated with Lagrangian stochastic (LS) models. Although these models have been employed successfully over land, the free surface at the air-sea interface complicates the implementation of traditional LS models. We present an adaptation of traditional LS models to the atmospheric marine boundary layer (MBL), where the bottom boundary is represented by a realistic wavy surface that moves and deforms. In addition, the correlation function for the turbulent flow following a particle is extended to the anisotropic, unsteady case. Our new model reproduces behaviour for Lagrangian turbulence in a stratified air flow that departs only slightly from the expected behaviour in isotropic turbulence. When solving for the trajectory of a heavy particle in the air flow, the modelled turbulent forcing on the particle also behaves remarkably well. For example, the spectrum of the turbulence at the particle location follows that of a massless particle for time scales approximately larger than the Stokes’ particle response time. We anticipate that this model will prove especially useful in the context of sea-spray dispersion and its associated momentum, sensible and latent heat, and gas fluxes between spray droplets and the atmosphere.

  13. Particle-hole pair states of layered materials

    NASA Astrophysics Data System (ADS)

    Lokot, Lyubov E.

    2015-04-01

    In the paper a theoretical study of both the quantized energies of excitonic states and their wave functions in gapped graphene and in monolayer of MoS2 is presented. An integral two-dimensional Schrödinger equation of the electron-hole pairing for particles with electron-hole symmetry of reflection is analytically solved. The solutions of Schrödinger equation in momentum space in gapped graphene and in the direct band monolayer of MoS2 by projection the two-dimensional space of momentum on the three-dimensional sphere are found. We analytically solve an integral two-dimensional Schrödinger equation of the electron-hole pairing for particles with electron-hole symmetry of reflection and with strong spin-orbit coupling. In monolayer of MoS2 as well as in single-layer graphene (SLG) the electron-hole pairing leads to the exciton insulator states. Calculating an integral two-dimensional Schrödinger equation of the electron-hole pairing for bilayer graphene, exciton insulator states with a gap 3 meV are predicted. The particle-hole symmetry of Dirac equation of layered materials allows perfect pairing between electron Fermi sphere and hole Fermi sphere in the valence band and conduction band and hence driving the Cooper instability.

  14. Fabrication of Nano-Composite Surface Layers on Aluminium Employing Friction Stir Processing Technique

    SciTech Connect

    Bozorg, S. F. K.; Zarghani, A. S.; Zarei-Hanzaki, A. [School of Metallurgy and Materials Engineering, Faculty of Engineering, University of Tehran, Tehran, P.O. Box: 14395-553 (Iran, Islamic Republic of)

    2010-03-11

    Al/Al{sub 2}O{sub 3} nano-composite surface layer was fabricated via friction stir processing technique. Commercial AA6082 aluminium alloy extruded bar and nanometric Al{sub 2}O{sub 3} powder were subjected to friction stir processing at a substrate travel speed of 80 mm/min and a tool rotation speed of 1000 rpm using a hardened H-13 tool steel. The grain structure and reinforcement particles were investigated by using optical and scanning electron microscopy. Results show that Al{sub 2}O{sub 3} particles can be more uniformly dispread in aluminium substrate by increasing the number of processing passes. Also, hardness enhancement of the nano-composite surface layer was found. This is attributed to uniform dispersion of Al{sub 2}O{sub 3} particles.

  15. Hypervelocity particle penetration in multi-layered thermal blankets

    NASA Technical Reports Server (NTRS)

    Liu, Jean; Niou, C.-S.; Murr, L. E.; Wang, P. W.

    1993-01-01

    Micrometeoroid and related hypervelocity particle impacts into 0.04-sq m samples cut from Scheldahl G411500 thermal blankets (STB) covering trays D05 and D07 in the NASA-LDEF satellite are characterized in detail. These impacts usually produced unique penetration features that generally consist of a delamination zone extending tens of penetration-hole diameters, separating the Teflon layer from the silver/Inconel film and the paint backing layers. When viewed from the space-facing side, the penetration holes are usually surrounded by rings or concentric halos within the delamination zone and radial cracks extending from the ejecta-rim surrounding the hole to the edge of the delamination zone. The phenomena responsible for the formation of these features are examined.

  16. Particle transport and flow modulation in particle-laden mixing layers

    NASA Astrophysics Data System (ADS)

    Tong, Xiao-Ling

    Shear flows provide a means to rapidly mix and disperse discrete solid particles and droplets in natural and industrial processes. Moderate mass loadings of particles in a gas mixing layer may also alter the gas shear flow. While the modeling of single-phase shear flows has undergone several decades of development and validation, the consideration of the corresponding problem in two- phase shear flows has just began. This dissertation represents a systematic effort to use a tool known as direct numerical simulations (DNS) to advance our understanding of particle transport and flow modulation in a gas mixing layer laden with solid particles. In DNS, almost all dynamically important flow scales are directly resolved. Previously, DNS of three-dimensional (3D) particle-laden shear flows have not been possible due to their high computational cost. Therefore, we first set out to develop and validate a computationally efficient and numerically accurate DNS methodology for particle-laden mixing layer. The method relies on a Fourier vorticity-based formulation together with a divergence-free decomposition. While almost all previous numerical studies adopted the trajectory approach for the dispersed phase in the context of DNS, a continuum approach has been developed and shown to reduce the computational time by a factor of 15 for the simulations of 3D particle-laden mixing layers. The validity and interpretation of the continuum approach were illustrated analytically with a stagnation point flow model. Detailed comparisons showed that the continuum approach and the trajectory approach yielded very similar results. Since the particulate field is compressible, numerical diffusion must be applied to remove local singularities. A dynamic-diffusion model has been developed as an optimum numerical diffusion model to ensure spectral resolution of particulate continuum fields. The numerical method was then used to study the interactions of finite-inertia particles with 3D flow structures. During the early stage of 3D mixing layer evolution, we found that 3D intense rib vortices can eject particles and add smaller scale features to the particulate concentration field. They could also cause a larger transverse dispersion of particles. The particles can selectively respond to new flow structures when the structures are at their peak intensity. The gradient transport closure model has been tested and shown to fail to predict the particulate mass flux correctly. Finally, flow modulation in 2D particle-laden mixing layers was studied both numerically and theoretically. At the linear instability stage, we found that the particles of large Stokes number can stabilize the gas flow while the particles with small inertia have destabilizing effect on the gas phase at finite flow Reynolds number. These qualitatively different effects have been shown to be directly related to the direction of interphase energy transfer. Particles of intermediate Stokes number have the strongest stabilizing effect on the gas flow. Nonlinear flow evolution showed vortex rollup and pairing with physical length scale of the order of the instability wavelength and time scale of the inverse of the linear growth rate. This coupling term acts as a forcing to the fluid vorticity equation, which, at intermediate Stokes number, leads to rupture of the vortices. In short, this dissertation study has laid down the groundwork for future studies on the modeling of turbulent two-phase flows.

  17. Compact Layer of Alkali Ions at the Surface of Colloidal Silica

    SciTech Connect

    Tikhonov,A.

    2007-01-01

    The forces of electrical imaging strongly polarize the surface of colloidal silica. I used X-ray scattering to study the adsorbed 2-nm-thick compact layer of alkali ions at the surface of concentrated solutions of 5-nm, 7-nm, and 22-nm particles, stabilized by either NaOH or a mixture of NaOH and CsOH, with the total bulk concentration of alkali ions ranging from 0.1 to 0.7 mol/L. The observed structure of the compact layer is almost independent of the size of the particles and the concentration of alkali base in the sol; it can be described by a two-layer model, that is, a {approx}6--8-{angstrom}-thick layer of directly adsorbed hydrated alkali ions with a surface concentration of {approx}3 x 10{sup 18} m{sup -2}, and a {approx}13-{angstrom}-thick layer with a surface concentration of sodium ions of {approx}8 x 10{sup 18} m{sup -2}. In cesium-enriched sols, Cs{sup +} ions preferentially adsorb in the first layer replacing Na{sup +}; their density in the second layer does not depend on the presence of cesium in the sol. The difference in the adsorption of Cs{sup +} and Na{sup +} ions can be explained by the ion-size-dependent term in the electrostatic Gibbs energy equation derived earlier by others. I also discuss the surface charge density and the value of surface tension at both the air/sol and the hexane/sol interfaces.

  18. Electronic structure of the surfaces of layered copper oxides

    SciTech Connect

    Prosandeyev, S.A.; Tennenboum, I.M. [Department of Physics, Rostov State University, 5 Zorge Street, 344104 Rostov on Don (Russian Federation)] [Department of Physics, Rostov State University, 5 Zorge Street, 344104 Rostov on Don (Russian Federation)

    1995-08-01

    The electronic structure of the surfaces of layered copper oxides has been investigated in the framework of a tight-binding model together with the unrestricted Hartree-Fock method. The main element of the layered copper oxides, namely the CuO{sub 2} layer, was supposed to lie parallel with the surface, as well as to be trimmed at a boundary of crystal. In the former case, the electrons at the surface were considered to be in an additional (surface) potential. A mode of the calculation of this potential has been developed on the basis of a method being similar to Ewald`s transformation. As an example, the surface of La{sub 2}CuO{sub 4} was studied. In the latter case, when the CuO{sub 2} layer is semi-infinite due to its cutting at the surface, the formation of electronic surface bands was carefully investigated. Both the metal and dielectric phases were examined. For the metal phase, we took into account the possible freezing of the spin-density wave at the surface. In all the cases, surface bands were present in the vicinity of the Fermi level. They had inherent, in the one-dimensional systems, peculiarities.

  19. Groupwise surface correspondence using particle filtering

    NASA Astrophysics Data System (ADS)

    Li, Guangxu; Kim, Hyoungseop; Tan, Joo Kooi; Ishikawa, Seiji

    2015-03-01

    To obtain an effective interpretation of organic shape using statistical shape models (SSMs), the correspondence of the landmarks through all the training samples is the most challenging part in model building. In this study, a coarse-tofine groupwise correspondence method for 3-D polygonal surfaces is proposed. We manipulate a reference model in advance. Then all the training samples are mapped to a unified spherical parameter space. According to the positions of landmarks of the reference model, the candidate regions for correspondence are chosen. Finally we refine the perceptually correct correspondences between landmarks using particle filter algorithm, where the likelihood of local surface features are introduced as the criterion. The proposed method was performed on the correspondence of 9 cases of left lung training samples. Experimental results show the proposed method is flexible and under-constrained.

  20. Modeling cross-hatch surface morphology in growing mismatched layers

    NASA Astrophysics Data System (ADS)

    Andrews, A. M.; Speck, J. S.; Romanov, A. E.; Bobeth, M.; Pompe, W.

    2002-02-01

    We propose and investigate a model for the development of cross-hatch surface morphology in growing mismatched layers. The model incorporates two important elements: (i) strain relaxation due to dislocation glide in the layer (film) interior that is also associated with misfit dislocation formation at the film/substrate interface and (ii) lateral surface transport that eliminates surface steps that originated from dislocation glide. A combination of dislocation-assisted strain relaxation and surface step flow leads to the appearance of surface height undulations during layer growth. A Monte Carlo simulation technique was applied to model dislocation nucleation events in the course of strain relaxation. The simulation was used to model the influence of dislocations on film surface height profiles. The surface height displacement was calculated from the analytic elasticity solutions for edge dislocations near a free surface. The results of the modeling predict that the average amplitude of the surface undulations and their apparent wavelength both increase with increasing film relaxation and film thickness. The developed cross-hatch pattern is characterized by an atomically smooth but mesoscopically (lateral dimensions ˜0.1-10 ?m) rough surface morphology. The conclusions of the model are in agreement with atomic force microscopy observations of cross-hatch surface relief in In0.25Ga0.75As/GaAs samples grown well beyond the critical thickness for misfit dislocation formation.

  1. Modification of arc emitted W particles in a model scrape-off layer plasma

    NASA Astrophysics Data System (ADS)

    Laux, M.; Balden, M.; Siemroth, P.

    2014-04-01

    In fusion machines (like e.g. ASDEX Upgrade and JET) equipped with W-coated plasma facing components (PFCs) arc tracks are observed post-mortem and W particles are identified as a component of the dust. Results from laboratory arcing of W-coated PFC-material concerning the size, velocity and direction of macro-particles are combined with model calculations of the heating, cooling and evaporation of W particles flying through a simplified scrape-off layer (SOL) plasma to assess the role of arc-produced particles as a source of W impurities. W atoms or ions eroded from a macro-particle flying across the SOL plasma are not subject to prompt re-deposition onto a PFC. Therefore, macro-particles constitute an essential source of W in the SOL and may even result in an impurity input into the region of confined plasma if the particle succeeds in pathing the SOL and crosses the last closed flux surface. The main result of the modelling is that a W particle from the large-size end of the distribution obtained in laboratory arcing and having a typical velocity (also known from laboratory experiment) is able to pass a SOL of 10 cm thickness filled with a realistic plasma and, finally, inject a certain amount of W-material into the confined plasma region.

  2. Role of surface active layers on localized breakdown of aluminum alloy 7075

    NASA Astrophysics Data System (ADS)

    Zhao, Zhijun

    Potentiodynamic polarization curves for AA7075-T6 in NaCl solution exhibit two breakdowns. The current increases at the first breakdown, reaches a peak and then decreases. At the second, higher breakdown potential, the current increases again. The second breakdown is dominated by sustained localized corrosion and the first one is believed to be associated with transient dissolution that precedes the onset of stable localized corrosion. This study is aimed at understanding the details of the transient dissolution phenomenon. The first breakdown mechanism of AA7xxx was studied by an in-situ observation system in which a combination of a magnified image of the surface with the instantaneous polarization curve allowed determination of the corrosion process as a function of potential. As-polished (to 1 mum) AA7075-T6 clearly exhibited dissolution of a thin surface layer corresponding to a sharp increase of current just above the first breakdown. No surface layer dissolution was observed for samples that were either ion milled or chemically etched to remove the effects of polishing. This susceptible surface layer was apparently the result of the mechanical polishing process. The surface microstructure of an as-polished sample was analyzed by TEM and several distinct features were found: (1) a unique thin layer with thickness of 100 nm on average; (2) many fewer fine hardening particles in the thin layer compared to bulk matrix, which means that the fine particles were destroyed and eliminated by polishing; (3) high aspect ratio nano-grains elongate along the final polishing direction; EDS analysis in STEM mode revealed a higher concentration of Zn at the nano-grain boundaries. The attack of the surface layer might initiate at the active nanograin boundary followed by nano-grain dissolution. Samples in other tempers were also examined. No surface layer dissolution and no first breakdown peak were observed for the solutionized + quenched alloy because no comparable Zn enriched bands were present and the composition of the surface layer was not substantially different than the bulk matrix. The solutionized samples did not contain hardening particles so there was no effect of the shearing on the surface composition. The overaged samples also exhibited no layer attack and only one breakdown potential. The particles in the overaged samples were larger and farther apart so that the shear associated with polishing was unable to destroy them fully. Zn-rich bands were observed at the nano-brain boundaries for the overaged temper, but the localized attack propagated into the bulk matrix rather than laterally as layer attack. Underaged samples showed thin layer dissolution and current peaks associated with a first breakdown phenomenon. However, the magnitude of the current peaks changed with the extent of aging as a result of differences in the hardness, and thus layer thickness and dissolution rate of the thin layer. A study of filiform corrosion (FFC) was performed on T6 and T7 temper samples either as-polished or chemically etched. FFC kinetics were higher on as-polished samples than on chemically etched samples, which confirmed higher activity of the altered surface layer induced by polishing. FFC on T6 sample of all the conditions was worse than T7 tempered samples.

  3. DNS of a Turbulent Boundary Layer with Surface Roughness

    Microsoft Academic Search

    Yi Chen; James Cardillo; Guillermo Araya; Luciano Castillo; Kenneth Jansen

    2010-01-01

    A Direct numerical simulation (DNS) of a high Reynolds number, zero pressure gradient, turbulent boundary layer (Retheta= 2400) subjected to sandpaper surface roughness is performed. The surface roughness is modeled with a roughness parameter k^+ ˜ 25 to match the experiments at similar Reynolds number and roughness distribution. The employed computational method involves a synergy of the multi-scale dynamic approach

  4. Entrainment of fine particles from surfaces by impinging shock waves

    Microsoft Academic Search

    G. T. Smedley; D. J. Phares; R. C. Flagan

    1999-01-01

    When a shock wave impinges on a surface, it reflects and propagates across the surface at supersonic velocity. The gas is impulsively accelerated by the passing shock wave. The resulting high-speed flow imparts sufficiently strong forces to particles on the surface to overcome strong adhesive forces and entrain the surface-bound particles into the gas. This paper describes an experimental study

  5. Acoustic tomography in the atmospheric surface layer

    Microsoft Academic Search

    A. Ziemann; K. Arnold; A. Raabe

    1998-01-01

    Acoustic tomography is presented as a technique for remote monitoring of meteorological quantities. This method and a special algorithm of analysis can directly produce area-averaged values of meteorological parameters. As a result consistent data will be obtained for validation of numerical atmospheric micro-scale models. Such a measuring system can complement conventional point measurements over different surfaces. The procedure of acoustic

  6. Acoustic tomography in the atmospheric surface layer

    Microsoft Academic Search

    A. Ziemann; K. Arnold; A. Raabe

    1999-01-01

    Acoustic tomography is presented as a technique for remote monitoring of meteorological quantities. This method and a special algorithm of analysis can directly produce area-averaged values of meteorological parameters. As a result consistent data will be obtained for validation of numerical atmospheric micro-scale models. Such a measuring system can complement conventional point measurements over different surfaces. The procedure of acoustic

  7. Surface properties of thin gold layers sputtered on polymers.

    PubMed

    Kolská, Z; Reznícková, A; Kvítek, O; Svorcík, V

    2012-08-01

    Thin gold layers were sputtered on the foils of polypropylene-PP, polyethyleneterephthalate-PET, polystyrene-PS, polyethylene-PE and polytetrafluoroethylene-PTFE modified by Ar+ plasma. Surface properties of pristine, plasma treated and gold coated polymers were characterized by two-points method (sheet electrical resistance), electrokinetical analysis (zeta-potential, surface chemistry), goniometry (contact angle), electron paramagnetic resonance (concentration of radicals), atomic force microscopy (AFM, surface morphology and roughness) and scratch test (mechanical properties). Zeta potential and contact angle, as assumed, differ dramatically for plasma treated polymers and for the polymers deposited by Au layers. AFM images indicate that after gold deposition on polymers the surface roughness and the surface morphology change depending on pristine polymer surfaces (roughness and morphology) and sputtering time. Electrical measurements resulted in fact that with increasing layer thickness, the sheet resistance of the gold layer decreases for all polymers with increasing sputtering time. Lower adhesive destruction is observed on the gold layer deposited on plasma treated PE in comparison with pristine. PMID:22962802

  8. Deposition of colloid particles on protein layers: fibrinogen on mica.

    PubMed

    Adamczyk, Z; Nattich, M; Wasilewska, M; Sadowska, M

    2011-04-15

    Colloid particle deposition was applied to characterize fibrinogen (Fb) monolayers on mica, which were produced by controlled adsorption under diffusion transport. By adjusting the time of adsorption and the bulk Fb concentration, monolayers of desired surface concentration were obtained. The surface concentration of Fb was determined directly by AFM enumeration of single molecules adsorbed over the substrate surface. It was proven that Fb adsorbed irreversibly on mica both at pH 3.5 and at pH 7.4 with the rate governed by bulk transport. The electrokinetic properties of Fb monolayers produced in this way were studied using the streaming potential method. The dependence of the apparent zeta potential of Fb monolayers was determined as a function of the coverage. It was shown that for pH 3.5 the initial negative zeta potential of the mica substrate was converted to positive for Fb coverage exceeding 0.16. On the other hand, for pH 7.4, the zeta potential of a Fb-covered mica remained negative for the entire coverage range. The charge distribution in Fb monolayers was additionally studied using the colloid deposition method, in which negatively and positively charged polystyrene latex particles (ca. 800 nm in diameter) were used. An anomalous deposition of negative latex particles on substrates exhibiting a negative zeta potential was observed. Results of these experiments were quantitatively interpreted in terms of the fluctuation theory assuming that adsorption sites consisted of two and three Fb molecules, for pH 3.5 and 7.4, respectively. These results suggested that for pH 7.4, the distribution of charge on Fb molecules was heterogeneous, characterized by the presence of positive patches, whereas the average zeta potential was negative, equal to -19 mV. The utility of the colloid deposition method for studying Fb monolayers was further demonstrated in deposition experiments involving positive latex particles. It was shown that for a rather broad range of fibrinogen coverage, both the positive and the negative latex particles can adsorb on surfaces covered by Fb, which behaved, therefore, as superadsorbing surfaces. It was also concluded that the colloid deposition method can be used to determine the Fb bulk concentration for the range inaccessible for other methods. PMID:21316698

  9. Study of the oxidized surface layer of titanium after annealing

    Microsoft Academic Search

    V. V. Peshkov; V. N. Milyutin

    1984-01-01

    mined. Electron microscope study of the surface topography was carried out in an AMR-1000 SEM by a secondary electron scheme and with an accelerating voltage of 20 kV. The structure of the oxidized surface layer was evaluated at magnification of i0,000 times or more, and the titanium surface was shadowed with gold followed by earthing of the whole specimen. Phase

  10. Lactobacillus surface layer proteins: structure, function and applications.

    PubMed

    Hynönen, Ulla; Palva, Airi

    2013-06-01

    Bacterial surface (S) layers are the outermost proteinaceous cell envelope structures found on members of nearly all taxonomic groups of bacteria and Archaea. They are composed of numerous identical subunits forming a symmetric, porous, lattice-like layer that completely covers the cell surface. The subunits are held together and attached to cell wall carbohydrates by non-covalent interactions, and they spontaneously reassemble in vitro by an entropy-driven process. Due to the low amino acid sequence similarity among S-layer proteins in general, verification of the presence of an S-layer on the bacterial cell surface usually requires electron microscopy. In lactobacilli, S-layer proteins have been detected on many but not all species. Lactobacillus S-layer proteins differ from those of other bacteria in their smaller size and high predicted pI. The positive charge in Lactobacillus S-layer proteins is concentrated in the more conserved cell wall binding domain, which can be either N- or C-terminal depending on the species. The more variable domain is responsible for the self-assembly of the monomers to a periodic structure. The biological functions of Lactobacillus S-layer proteins are poorly understood, but in some species S-layer proteins mediate bacterial adherence to host cells or extracellular matrix proteins or have protective or enzymatic functions. Lactobacillus S-layer proteins show potential for use as antigen carriers in live oral vaccine design because of their adhesive and immunomodulatory properties and the general non-pathogenicity of the species. PMID:23677442

  11. SPLITTING OF THE Al SURFACE PLASMON DISPERSION CURVES BY Ag SURFACE LAYERS

    E-print Network

    Paris-Sud XI, Université de

    645 SPLITTING OF THE Al SURFACE PLASMON DISPERSION CURVES BY Ag SURFACE LAYERS T. LOPEZ-RIOS, F], the existence of coupled surface plasmon modes in metallic slabs is well established. Such coupled modes have of the metallic film is large enough, the modes are nearly decoupled and tend towards the two surface plasmon

  12. Atomic and molecular layer deposition for surface modification

    SciTech Connect

    Vähä-Nissi, Mika, E-mail: mika.vaha-nissi@vtt.fi [VTT Technical Research Centre of Finland, PO Box 1000, FI?02044 VTT (Finland); Sievänen, Jenni; Salo, Erkki; Heikkilä, Pirjo; Kenttä, Eija [VTT Technical Research Centre of Finland, PO Box 1000, FI?02044 VTT (Finland); Johansson, Leena-Sisko, E-mail: leena-sisko.johansson@aalto.fi [Aalto University, School of Chemical Technology, Department of Forest Products Technology, PO Box 16100, FI?00076 AALTO (Finland); Koskinen, Jorma T.; Harlin, Ali [VTT Technical Research Centre of Finland, PO Box 1000, FI?02044 VTT (Finland)

    2014-06-01

    Atomic and molecular layer deposition (ALD and MLD, respectively) techniques are based on repeated cycles of gas–solid surface reactions. A partial monolayer of atoms or molecules is deposited to the surface during a single deposition cycle, enabling tailored film composition in principle down to molecular resolution on ideal surfaces. Typically ALD/MLD has been used for applications where uniform and pinhole free thin film is a necessity even on 3D surfaces. However, thin – even non-uniform – atomic and molecular deposited layers can also be used to tailor the surface characteristics of different non-ideal substrates. For example, print quality of inkjet printing on polymer films and penetration of water into porous nonwovens can be adjusted with low-temperature deposited metal oxide. In addition, adhesion of extrusion coated biopolymer to inorganic oxides can be improved with a hybrid layer based on lactic acid. - Graphical abstract: Print quality of a polylactide film surface modified with atomic layer deposition prior to inkjet printing (360 dpi) with an aqueous ink. Number of printed dots illustrated as a function of 0, 5, 15 and 25 deposition cycles of trimethylaluminum and water. - Highlights: • ALD/MLD can be used to adjust surface characteristics of films and fiber materials. • Hydrophobicity after few deposition cycles of Al{sub 2}O{sub 3} due to e.g. complex formation. • Same effect on cellulosic fabrics observed with low temperature deposited TiO{sub 2}. • Different film growth and oxidation potential with different precursors. • Hybrid layer on inorganic layer can be used to improve adhesion of polymer melt.

  13. Effect of surface chemistry and metallic layer thickness on the clustering of metallodielectric Janus spheres.

    PubMed

    Shemi, Onajite; Solomon, Michael J

    2014-12-30

    The noncovalent binding of the gold hemispheres of polystyrene/gold colloidal Janus spheres in aqueous solution was found to depend more significantly on the deposition thickness of the particle's gold layer than the chemistry of a covalently affixed self-assembled monolayer on the gold. By means of two-channel confocal laser scanning microscopy, salt-induced clustering was observed and quantified for Janus particles with gold hemispheres functionalized with a thiol self-assembled monolayer that varied in hydrophobicity and chain length. The thickness of the gold layer on the Janus particles was also varied from 10 to 40 nm. The measured cluster distributions were strongly salt dependent, with clustering absent at 1 mM salt but present at salt concentrations in the range of 2-3 mM. For Janus spheres with a 40 nm thick gold hemisphere, the effects of both thiol monolayer hydrophobicity and chain length were modest. Varying the gold layer thickness from 10 to 40 nm, however, had a significant effect on the cluster distribution; the most abundant cluster size shifted from one to seven particles as the gold layer thickness increased from 10 to 40 nm. Thus, the gold layer thickness had an effect stronger than that of either self-assembled monolayer hydrophobicity or chain length on the self-assembly of metallodielectric Janus particles into clusters. The dominant effect of the metallic layer thickness suggests that van der Waals forces between metallic surfaces are more important than hydrophobic interactions in determining the pair potential interactions of metallodielectric Janus particles. PMID:25469598

  14. Effect of diffusion saturation with oxygen on the surface-layer structure and mechanical properties of niobium alloys

    Microsoft Academic Search

    L. I. Emel'yanova; A. I. Chernitsyn

    1978-01-01

    Conclusions 1.The interaction of niobium alloy 5VMTs, with oxygen within the temperature range 600–900°C changes ambiguously with increasing temperature and takes place with the preferential formation of excess-phase particles in the surface layers at 600 and 900°C, while deep and intensive saturation without the formation of oxides occurs at 800°C.2.Saturation of the surface layer to a depth comprising 2–6% of

  15. Laser controlled melting of HSLA steel surface with presence of B4C particles

    NASA Astrophysics Data System (ADS)

    Yilbas, B. S.; Patel, F.; Karatas, C.

    2013-10-01

    Laser gas assisted melting of high strength low alloy steel surface is carried out. The alloy surface is pre-prepared to contain 5% B4C particles in a 40 ?m thick carbon film prior to laser treatment process. Metallurgical and morphological changes in the laser treated layer are examined by using scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction. The residual stress developed and the microhardness of the resulting surface is measured. It is found that B4C particles remain in solid phase in the surface region due to their high melting temperature. The dense layer consisting of fine grains are formed at the surface and the feathery like structure is observed below the surface vicinity, which consists of martensite and nitride precipitations. The use of nitrogen at high pressure causes the formation of nitride compounds at the surface, which contributes to the volume shrinkage in the dense layer. Surface microhardness increases considerably because of attainment of high cooling rates, formation of nitride compounds, and presence of B4C particles at the surface.

  16. Synthesis and characterization of macromolecular layers grafted to polymer surfaces

    NASA Astrophysics Data System (ADS)

    Burtovyy, Oleksandr

    The composition and behavior of surfaces and interfaces play a pivotal role in dictating the overall efficiency of the majority of polymeric materials and devices. Surface properties of the materials can be altered using surface modification techniques. It is necessary to highlight that successful methods of surface modification should affect only the upper layer of the polymer material without changing bulk properties. The processes must introduce new functionalities to the surface, optimize surface roughness, lubrication, hydrophobicity, hydrophilicity, adhesion, conductivity, and/or biocompatibility. Research presented in this dissertation is dedicated to the synthesis, characterization, and application of thin macromolecular layers anchored to polymer substrates. Specifically, attachment of functional polymers via a "grafting to" approach has been extensively studied using PET and nylon model substrates. First, poly(glycidyl methacrylate) was used to introduce permanent functionalities to the model substrates by anchoring it to model films. Then, three different functional polymers were grafted on top of the previous layer. As one part of this study, the temperature and time dependence of grafting functional layers were studied. The surface coverage by hydrophobic polymer was determined from experimental data and predicted by a model. In general, the model has a high degree of predictive capability. Next, surface modification of polymeric fibers and membranes is presented as an important application of the polymer thin layers targeted in the study. Specifically, the procedures developed for surface modification of model substrates was employed for modification of PET, nylon, and cotton fabrics as well as PET track-etched membranes. Since epoxy groups are highly reactive in various chemical reactions, the approach becomes virtually universal, allowing both various surfaces and end-functionalized macromolecules to be used in the grafted layer synthesis. PET membranes modified with a reactive anchoring layer can be successfully used to build membrane assemblies by incorporating silica, aluminum, or titanium oxide microparticles as spacers. It is expected that the proposed approaches for the surface modification of the membranes and for the generation of multilayered membrane assemblies can be employed straightforwardly to provide an efficient platform for fabrication of breathable protective materials. Characterization of modified membranes with a cantilever-based method, which can be used for prediction of properties and behavior of thin grafted films, is reported. This technique can be used as a method for fast screening of modified membranes. The method is very robust and capable of detecting very small quantities of substance adsorbed; kinetics of the process can be tracked, as well. This approach can be further developed as a handheld sensor for early warning of the presence of chemical vapors and nerve agents.

  17. Surface Collisions Involving Particles and Moisture (SCIP'M)

    NASA Technical Reports Server (NTRS)

    Davis, Robert H.

    2005-01-01

    Experiments were performed on the collision of a solid sphere with a nearly horizontal flat surface covered with a thin layer of viscous liquid. High-speed collisions were obtained by dropping the ball onto the surface from various heights, using gravitational acceleration. Low-speed collisions were obtained using pendulums with long strings or by launching the balls at low velocities in the reduced-gravity environment of parabolic flight. The sphere bounces only when the impact velocity exceeds a critical value. The coefficient of restitution (ratio of rebound velocity to impact velocity) increases with increasing impact velocity above the critical value, indicating the increasing relative importance of elastic deformation to viscous dissipation. The critical impact velocity increases, and the coefficient of restitution decreases, with increasing viscosity or thickness of the liquid layer and with decreasing density or size of the sphere. The ratio of the wet and dry coefficients is expressed as a function of the Stokes number (ratio of particle inertia and viscous forces), showing good agreement between theory and experiment. Similar experiments were performed with the flat surface inclined at various angles to the approaching sphere. A modified Stokes number, which is a measure of the ratio of inertia of the sphere in the normal direction to the viscous forces exerted by the fluid layer, was used for the analysis of oblique collisions. Even for these oblique collisions, it was found that no rebound of the ball was observed below a certain critical Stokes number. The coefficient of normal restitution, defined as a ratio of normal rebound velocity to normal approach velocity, was found to increase beyond the critical Stokes number and even out as it approaches the value for dry restitution at high Stokes numbers. It was also found that, for smooth spheres like steel, the normal restitution at the same modified Stokes number is independent of the angle of impact. The tangential coefficient of restitution, defined as the ratio of tangential rebound velocity to tangential approach velocity, is found to be nearly unity, except for very low approach velocities. Thus, as a first approximation, the theories that predict the coefficient of restitution for head-on wet collisions can be extended to predict the coefficient of normal restitution for oblique wet collisions. Additional experiments were performed with soft surfaces in which a porous cloth or sponge layer was placed over the hard, flat surface. In these experiments, the coefficient of restitution was found to decrease with increasing impact velocity, due to inelastic losses in the soft material. A model combining inelastic deformation and flow through porous media was developed to describe these findings.

  18. Alternative barrier layers for surface covers in dry climates

    SciTech Connect

    Stormont, J.C.

    1994-09-01

    Surface covers are one of the most widespread remediation and waste management options in all climates. Barrier layers to limit percolation through cover systems are principal features of engineered, multi-component cover designs. Conventional barrier layer components developed for humid climates have limitations in dry climates. One alternative barrier layer is a capillary barrier, which consists of a fine-over-coarse soil arrangement. The capacity of capillary barrier to laterally divert downward moving water is the key to their success. Another alternative is a dry barrier, in which atmospheric air is circulated through a coarse layer within the cover to remove water vapor. Incorporating a coarse layer which stores water for subsequent removal by air flow reduces the requirements for the air flow velocity and increases the applicability of the dry barrier.

  19. 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.

  20. An experimental investigation of turbulent boundary layers along curved surfaces

    NASA Technical Reports Server (NTRS)

    So, R. M. C.; Mellor, G. L.

    1972-01-01

    A curved wall tunnel was designed, and an equilibrium turbulent boundary layer was set up on the straight section preceding the curved test section. Turbulent boundary layer flows with uniform and adverse pressure distributions along convex and concave walls were investigated. Hot-wire measurements along the convex surface indicated that turbulent mixing between fluid layers was very much reduced. However, the law of the wall held and the skin friction, thus determined, correlated well with other measurements. Hot-wire measurements along the concave test wall revealed a system of longitudinal vortices inside the boundary layer and confirmed that concave curvature enhances mixing. A self-consistent set of turbulent boundary layer equations for flows along curved surfaces was derived together with a modified eddy viscosity. Solution of these equations together with the modified eddy viscosity gave results that correlated well with the present data on flows along the convex surface with arbitrary pressure distribution. However, it could only be used to predict the mean characteristics of the flow along concave walls because of the existence of the system of longitudinal vortices inside the boundary layer.

  1. Particles in Surface Waters: Coagulation and Transport

    E-print Network

    Culkin, Gerald W.; Lawler, Desmond F.

    -averaged, unsteady particle transport were developed to approximate the size-dependent particle transport processes, which included advection, dispersion, and settling. Coupled exchange of discrete particles between the water column and sediment bed was modeled using...

  2. Re-suspension Process In Turbulent Particle-fluid Mixture Boundary Layers

    NASA Astrophysics Data System (ADS)

    Zwinger, T.; Kluwick, A.

    Many theoretical applications of geophysical flows, such as sediment transport (e.g. Jenkins &Hanes, 1998) and aeolian transport of particles (e.g. Hopwood et al., 1995) utilize concepts for describing the near wall velocity profiles of particle suspensions originally arising from classical single phase theories. This approach is supported by experiments indicating the existence of a logarithmic fluid velocity profile similar to single phase flows also in case of high Reynolds number wall bounded particle sus- pension flows with low particle volume fractions (Nishimura &Hunt, 2000). Since the concept of a logarithmic near wall profile follows from classic asymptotic the- ory of high Reynolds number wall bounded flows the question arises to what extent this theory can be modified to account for particles being suspended in the ambient fluid. To this end, the asymptotic theory developed by Mellor (1972) is applied to the Favré-averaged equations for the carrier fluid as well as the dispersed phase derived on the basis of a volume averaged dispersed two-phase theory (Gray &Lee, 1977). Numerical solutions for profiles of main stream velocities and particle volume frac- tion in the fully turbulent region of the boundary layer for different turbulent Schmidt numbers are computed applying a Finite Difference box scheme. In particular, atten- tion is focused on the turbulent re-suspension process of particles from dense granular flow adjacent to the bounding surface into the suspension. From these results boundary conditions in form of wall functions for velocities as well as the volume fraction of the particles can be derived and the validity of analogy laws between turbulent mass and momentum transfer at the bounding surface can be proved from an asymptotic point of view. The application of these concepts in the field of snow avalanche simulation (Zwinger, 2000) is discussed.

  3. Particle morphological and roughness controls on mineral surface charge development

    NASA Astrophysics Data System (ADS)

    Boily, Jean-François; Kozin, Philipp A.

    2014-09-01

    Effects of mineral particle morphology and roughness on potential determining ion (p.d.i.; H+, OH-) loadings achieved at synthetic lepidocrocite (?-FeOOH) surfaces were predominantly investigated by potentiometry and thermodynamic modeling. Nanosized rod- (RL) and lath-shaped (LL) particles exhibiting different proportions of the same predominant crystallographic faces acquired largely comparable pH, ionic strength and counterion (NaCl, NaClO4) dependencies on p.d.i. loadings. These results supported previous claims that faces ideally containing proton silent sites only, are likely populated by additional proton active sites. This concept was supported further by results of roughened LL-like particles (LLR) also showing highly congruent pH-, ionic strength- and composition-dependent p.d.i. loadings with those of LL and RL. These loadings thereby correspond to maximal levels allowed by net attractive and repulsive forces at each solution composition, irrespective of particle morphology. Contrasting equilibration times required to achieve these loadings revealed considerably slower exchange of p.d.i. and electrolyte ions near the point of zero charge in the rough LLR than in the more idealized LL and RL particles. Thermodynamic modeling was used to test various concepts accounting for these results. The model made use of a novel framework capable of isolating electrostatic contributions from different faces, and of accounting for ion-specific double-layer properties within a single crystallographic face. These efforts made use of capacitance values for each electrolyte ions within the framework of a recently developed Variable Capacitance Model. Attempts at modeling all three particle types were used to suggest that the (0 1 0) face contains ?0.9 site nm-2 of proton active sites, a value notably constrained by recently published Na+, Cl-, and ClO4- loadings derived by cryogenic X-ray photoelectron spectroscopy. The model presented in this work thus provides a means to predict p.d.i. loadings on multifaceted mineral particle surfaces, and can therefore be used to constrain further our understanding of mineral/water interface reactivity.

  4. Surface modification of gold nanorods using layer-by-layer technique for cellular uptake

    Microsoft Academic Search

    Hironobu Takahashi; Takuro Niidome; Takahito Kawano; Sunao Yamada; Yasuro Niidome

    2008-01-01

    Gold nanorods (NRs), rod-shaped gold nanoparticles, were modified with bovine serum albumin (BSA) and polyethylenimine (PEI)\\u000a using layer-by-layer technique. From absorption spectroscopy and zeta potential measurements, it was obvious that NRs were\\u000a wrapped with these polymers without aggregation of NRs. Following BSA modification, the surface-modified NRs (BSA-NRs) were\\u000a well-dispersed without aggregation in biochemical conditions, verified from absorption spectroscopy. Further modification

  5. An Aerosol Model of the Marine and Coastal Atmospheric Surface Layer

    Microsoft Academic Search

    G. A. Kaloshin; I. A. Grishin

    2011-01-01

    We present a microphysical model for the surface layer marine and coastal atmospheric aerosols that is based on long-term observations of size distributions for 0.01–100 µm particles. The fundamental feature of the model is a parameterization of amplitudes and widths for aerosol modes of the aerosol size distribution function (ASDF) as functions of fetch and wind speed. The shape of

  6. Alumina atomic layer deposition nanocoatings on primary diamond particles using a fluidized bed reactor

    E-print Network

    George, Steven M.

    Alumina atomic layer deposition nanocoatings on primary diamond particles using a fluidized bed]. Atomic layer deposition (ALD) is a nanocoating process that is an ideal method for such an application

  7. Measurements of Kinetic Energy Loss for Particles Impacting Surfaces

    Microsoft Academic Search

    Stephen Wall; Walter John; Hwa-Chi Wang; Simon L. Goren

    1990-01-01

    Incoming and rebounding particle velocities were measured to within several particle diameters of the impaction surface using laser Doppler velocimetry. Impacts occurred normal to the surface and ranged from 1 m\\/s, near the threshold for particle bounce, to 100 m\\/s, well into the plastic damage regime. Monodisperse ammonium fluorescein spheres, 2.6–6.9 ?m in diameter, impacted target surfaces including polished molybdenum

  8. Particle impact tests. [simulation of micrometeoroid damage to orbiter surface

    NASA Technical Reports Server (NTRS)

    Komatsu, G. K.

    1978-01-01

    Particle impact tests were performed on three types of orbiter surface with a micrometeoroid facility. The test equipment electrostatically accelerated micron sized particles to high velocities simulating micrometeoroid impacts. Test particles were titanium diboride with typical velocities in the range 1 to 2.3 km x sec/1 and equivalent particle diameters in the range 4 to 16 microns. Impact angles to the material surface were 90, 60 and 30 degrees. The particle impact sites were located on the sample surfaces and craters were photographed with a magnification of 400X.

  9. Determination of colloidal particle surface charge from dielectrophoresis

    NASA Astrophysics Data System (ADS)

    Chavez, Marko; Nuansri, Rittirong; Mazza, Jacob; Ou-Yang, H. Daniel

    2015-03-01

    Electrophoresis (EP) is used to determine colloidal particle surface charge. However, when the Debye length is comparable to or larger than the particle size, electrophoresis cannot be reliably used to determine the surface charge due to counter ion retardation flow. Alexander et al. developed a theory relating colloidal osmotic pressure and particle surface charge. We use dielectrophoresis (DEP) to obtain a potential landscape based on the number density distribution of the particles in a non-uniform AC electric field. We determine the osmotic pressure from the DEP force and density profiles using Einstein's osmotic equilibrium equation. Surface charge obtained by DEP (thermodynamics) will be compared to that obtained by EP (electrokinetics).

  10. Surface Energy Balance and The Mixed Layer at Lake Tanganyika

    NASA Astrophysics Data System (ADS)

    Verburg, P.; Hecky, R.

    2002-12-01

    Lake Tanganyika is a very large (670 by 50 km) and deep rift lake (max depth 1.5 km) in East Africa between 3.5 and 9 degree south of the equator. Mixing of the upper layers in this meromictic lake is most intense in the trade wind season (May - September). Apart from increased wind speeds, lower air temperatures and evaporative cooling of the surface layer combine to enhance mixing. Previous work indicated that correlation of evaporation and heat loss from the lake leaves room for a significant portion in the variability of heat content to be explained by other factors. The components of the energy balance which contribute to mixing were compared among seasons and between the north and south ends of the lake, over diel and annual cycles. Sensible heat and latent heat fluxes were estimated with bulk aerodynamic formulas and the heat storage change in the surface water layer was determined. Solar radiation was measured and longwave and all-wave net radiation calculated. Evaporation provided a major contribution to mixing but varied per site and over seasons. Mixing intensity was related to oxygen and nutrient cycles. Apart from evaporative cooling, sensible heat transfer and the emission of long wave radiation were important mechanisms in cooling the surface layer at night. Sensible heat transfer and outgoing longwave radiation were relatively more important at the north end of the lake, compared with the south end, in explaining nocturnal heat loss from the surface.

  11. Shape-selective sieving layers on an oxide catalyst surface

    E-print Network

    Mohseni, Hooman

    Shape-selective sieving layers on an oxide catalyst surface Christian P. Canlas1 , Junling Lu2 such as zeolites, metal­organic frameworks and mesostructured oxides are of immense practical utility for gas of molecules or can modify the product selectivity (regioselectivity or enantioselectivity) of catalyst sites

  12. Reflection from Layered Surfaces due to Subsurface Scattering Pat Hanrahan

    E-print Network

    Ramamoorthi, Ravi

    Reflection from Layered Surfaces due to Subsurface Scattering Pat Hanrahan Department of Computer Research Center for Computer Science Abstract The reflection of light from most materials consists of two ma- jor terms: the specular and the diffuse. Specular reflection may be modeled from first principles

  13. Thermal stability of nanocrystalline layers fabricated by surface nanocrystallization

    Microsoft Academic Search

    Yong-jin Mai; Xiao-hua Jie; Li-li Liu; Neng Yu; Xiang-xin Zheng

    2010-01-01

    A nanocrystalline layer with ultrafine grains (about 30–40nm) on the surface of 7050 aluminum alloy was fabricated by a new technique called High Pressure Shot Peening (HPSP) which is the combination of common Shot Peening equipment with a pressurizing vessel. Relationship between hot flow and temperature was observed by Differential Scanning Calorimetry (DSC) and the activation energy, calculated by Kisssinger

  14. NMR of thin layers using a meanderline surface coil

    DOEpatents

    Cowgill, Donald F. (San Ramon, CA)

    2001-01-01

    A miniature meanderline sensor coil which extends the capabilities of nuclear magnetic resonance (NMR) to provide analysis of thin planar samples and surface layer geometries. The sensor coil allows standard NMR techniques to be used to examine thin planar (or curved) layers, extending NMRs utility to many problems of modern interest. This technique can be used to examine contact layers, non-destructively depth profile into films, or image multiple layers in a 3-dimensional sense. It lends itself to high resolution NMR techniques of magic angle spinning and thus can be used to examine the bonding and electronic structure in layered materials or to observe the chemistry associated with aging coatings. Coupling this sensor coil technology with an arrangement of small magnets will produce a penetrator probe for remote in-situ chemical analysis of groundwater or contaminant sediments. Alternatively, the sensor coil can be further miniaturized to provide sub-micron depth resolution within thin films or to orthoscopically examine living tissue. This thin-layer NMR technique using a stationary meanderline coil in a series-resonant circuit has been demonstrated and it has been determined that the flat meanderline geometry has about he same detection sensitivity as a solenoidal coil, but is specifically tailored to examine planar material layers, while avoiding signals from the bulk.

  15. Many-body microhydrodynamics of colloidal particles with active boundary layers

    NASA Astrophysics Data System (ADS)

    Singh, Rajesh; Ghose, Somdeb; Adhikari, R.

    2015-06-01

    Colloidal particles with active boundary layers—regions surrounding the particles where non-equilibrium processes produce large velocity gradients—are common in many physical, chemical and biological contexts. The velocity or stress at the edge of the boundary layer determines the exterior fluid flow and, hence, the many-body interparticle hydrodynamic interaction. Here, we present a method to compute the many-body hydrodynamic interaction between N spherical active particles induced by their exterior microhydrodynamic flow. First, we use a boundary integral representation of the Stokes equation to eliminate bulk fluid degrees of freedom. Then, we expand the boundary velocities and tractions of the integral representation in an infinite-dimensional basis of tensorial spherical harmonics and, on enforcing boundary conditions in a weak sense on the surface of each particle, obtain a system of linear algebraic equations for the unknown expansion coefficients. The truncation of the infinite series, fixed by the degree of accuracy required, yields a finite linear system that can be solved accurately and efficiently by iterative methods. The solution linearly relates the unknown rigid body motion to the known values of the expansion coefficients, motivating the introduction of propulsion matrices. These matrices completely characterize hydrodynamic interactions in active suspensions just as mobility matrices completely characterize hydrodynamic interactions in passive suspensions. The reduction in the dimensionality of the problem, from a three-dimensional partial differential equation to a two-dimensional integral equation, allows for dynamic simulations of hundreds of thousands of active particles on multi-core computational architectures. In our simulation of 104 active colloidal particle in a harmonic trap, we find that the necessary and sufficient ingredients to obtain steady-state convective currents, the so-called ‘self-assembled pump’, are (a) one-body self-propulsion and (b) two-body rotation from the vorticity of the Stokeslet induced in the trap.

  16. Application of Atmospheric Plasma-Sprayed Ferrite Layers for Particle Accelerators

    E-print Network

    Caspers, F; Federmann, S; Taborelli, M; Schulz, C; Bobzin, K; Wu, J

    2013-01-01

    A common problem in all kinds of cavity-like structures in particle accelerators is the occurrence of RF-resonances. Typically, ferrite plates attached to the walls of such structures as diagnostic devices, kickers or collimators, are used to dampen those undesired modes. However, the heat transfer rate from these plates to the walls is rather limited. Brazing ferrite plates to the walls is not possible in most cases due to the different thermal expansion coefficients. To overcome those limitations, atmospheric plasma spraying techniques have been investigated. Ferrite layers with a thickness from 50 ?m to about 300 ?m can be deposited on metallic surfaces like stainless steel exhibiting good thermal contact and still reasonable absorption properties. In this paper the technological aspects of plasma deposition are discussed and results of specifically developed RF loss measurement procedures for such thin magnetically lossy layers on metal are presented.

  17. Hygroscopic behavior and liquid-layer composition of aerosol particles generated from natural and artificial seawater

    Microsoft Academic Search

    Matthew E. Wise; Evelyn J. Freney; Corey A. Tyree; Jonathan O. Allen; Scot T. Martin; Lynn M. Russell; Peter R. Buseck

    2009-01-01

    Sea-salt aerosol (SSA) particles affect the Earth's radiative balance and moderate heterogeneous chemistry in the marine boundary layer. Using conventional and environmental transmission electron microscopes (ETEM), we investigated the hygroscopic growth and liquid-layer compositions of particles generated from three types of aqueous salt solutions: sodium chloride, laboratory-synthesized seawater (S-SSA particles), and natural seawater (N-SSA particles). Three levels of morphological change

  18. Entrainment of fine particles from surfaces by impinging shock waves

    Microsoft Academic Search

    G. T. Smedley; D. J. Phares; R. C. Flagan

    1999-01-01

    When a shock wave impinges on a surface, it reflects and propagates across the surface at supersonic velocity. The gas is\\u000a impulsively accelerated by the passing shock wave. The resulting high-speed flow imparts sufficiently strong forces to particles\\u000a on the surface to overcome strong adhesive forces and entrain the surface-bound particles into the gas. This paper describes\\u000a an experimental study

  19. Electrocompression of the Au(111) Surface Layer during Au Electrodeposition

    NASA Astrophysics Data System (ADS)

    Ayyad, A. H.; Stettner, J.; Magnussen, O. M.

    2005-02-01

    In situ grazing-incidence x-ray diffraction studies of reconstructed Au(111) electrodes in aqueous electrolyte solutions are presented, which reveal a significantly increased compression of the Au surface layer during Au electrodeposition as compared to Au(111) surfaces under ultrahigh vacuum conditions or in the Au-free electrolyte. The compression increases towards more negative potentials, reaching 5.3% at the most negative potentials studied. It may be explained within a simple thermodynamic model by a release of potential-induced surface stress.

  20. Magnetic properties of FINEMET with excimer laser treated surface layers

    NASA Astrophysics Data System (ADS)

    Kollár, P.; Ramin, D.; Zele?; Áková, A.; Riehemann, W.; Ku?; Mi?; Ski, M.

    1999-08-01

    The positive influence of laser treating on the decrease of power losses of many soft magnetic materials (as well as nanocrystalline FINEMET) is well known. The surface defects cause refinement of the domain structure producing small domains with movable domain walls. Such a refinement is one of the ways of reducing dynamic loss at higher frequencies which is dominant in the total power loss. We found that surface defects in the form of relatively shallow grooves produced by the excimer laser treatment are not sufficient to influence the bulk coercivity, but they do influence the surface-layer coercivity and domain structure.

  1. Particle-induced indentation of the alveolar epithelium caused by surface tension forces

    PubMed Central

    Kojic, M.; Tsuda, A.

    2010-01-01

    Physical contact between an inhaled particle and alveolar epithelium at the moment of particle deposition must have substantial effects on subsequent cellular functions of neighboring cells, such as alveolar type-I, type-II pneumocytes, alveolar macrophage, as well as afferent sensory nerve cells, extending their dendrites toward the alveolar septal surface. The forces driving this physical insult are born at the surface of the alveolar air-liquid layer. The role of alveolar surfactant submerging a hydrophilic particle has been suggested by Gehr and Schürch's group (e.g., Respir Physiol 80: 17–32, 1990). In this paper, we extended their studies by developing a further comprehensive and mechanistic analysis. The analysis reveals that the mechanics operating in the particle-tissue interaction phenomena can be explained on the basis of a balance between surface tension force and tissue resistance force; the former tend to move a particle toward alveolar epithelial cell surface, the latter to resist the cell deformation. As a result, the submerged particle deforms the tissue and makes a noticeable indentation, which creates unphysiological stress and strain fields in tissue around the particle. This particle-induced microdeformation could likely trigger adverse mechanotransduction and mechanosensing pathways, as well as potentially enhancing particle uptake by the cells. PMID:20634359

  2. NEUTRON DIFFRACTION MEASUREMENT OF RESIDUAL STRESSES IN FRICTION STIR PROCESSED NANOCOMPOSITE SURFACE LAYER

    SciTech Connect

    Xu, Hanbing [ORNL; Hubbard, Camden R [ORNL; An, Ke [ORNL; Wang, Xun-Li [ORNL; Feng, Zhili [ORNL; Qu, Jun [ORNL

    2009-01-01

    Friction stir processing (FSP) was successfully used to stir and mix nano-sized Al2O3 particles into a Al6061-T6 aluminum plate to form a nanocomposite layer up to 3 mm thick. This nanocomposite surface has demonstrated significantly improved surface hardness, yield strength, and wear-resistance without sacrificing the substrate ductility and conductivity. Neutron diffraction analysis was conducted to determine the residual stress distribution in the nanocomposite surface layer. For comparison, the residual stress of the aluminum surface that was processed similarly but had no particle involved was also measured. Results showed that the macro-level residual stresses in the FSP zone without particles are low due to the annealing effect induced by the long heating time and large heat input. The macro-level residual stresses in the FSP-processed Al-Al2O3 nanocomposite zone are tensile up to 100 MPa in all three directions. The details of the results will be further discussed in the paper.

  3. Particle resuspension and associated coherent structures in a turbulent boundary layer

    NASA Astrophysics Data System (ADS)

    Braaten, David Alan

    Fundamental properties of particle resuspension from a surface solely by turbulent fluid forces was examined experimentally by observing intermittent particle resuspension and associated turbulent flow properties. Experiments were conducted in an environmental wind tunnel, where sparse beds of monodisperse Lycopodium spores (Club Moss) were placed flush with the floor of the wind tunnel, and exposed to a steady, well developed turbulent boundary layer flow. Particle bed concentration was monitored in situ throughout each experimental trial using an optical system designed to detect forward scattering from a HeNe laser beam. Simultaneous measurements of streamwise and vertical velocity were made immediately downstream of the illuminated particles using hot film anemometry. Experimental trials were conducted at three free-stream velocities (6.0, 7.5, and 9.0 m s(-1)) for a duration of 35 minutes. A Monte-Carlo particle resuspension model was developed to simulate the resuspension process associated with coherent structures of varying magnitude. Simulations were compared with experimental results to identify a probability distribution of coherent structure magnitude.

  4. A surface science investigation of the formation of passivating layers on copper surfaces 

    E-print Network

    Hamelin, Elizabeth I.

    1996-01-01

    A SURFACE SCIENCE INVESTIGATION OF THE FORMATION OF PASSIVATING LAYERS ON COPPER SURFACES A Thesis by ELIZABETH I. ~IN Submitted to the Office of Graduate Studies of Texas A@M University in partial fulfillment of the requirements... for the degree of MASTER OF SCIENCE December 1996 Major Subject: Chemistry A SURFACE SCIENCE INVESTIGATION OF THE FORMATION OF PASSIVATING I. AYERS ON COPPER SURFACES A Thesis by ELIZABETH I. ~IN Submitted to Texas A&M University in partial fulfillment...

  5. Alpha particle backscattering measurements used for chemical analysis of surfaces

    NASA Technical Reports Server (NTRS)

    Patterson, J. H.

    1967-01-01

    Alpha particle backscattering performs a chemical analysis of surfaces. The apparatus uses a curium source and a semiconductor detector to determine the energy spectrum of the particles. This in turn determines the chemical composition of the surface after calibration to known samples.

  6. Comparing surface particle coverage predictions with image analysis measurements

    Microsoft Academic Search

    Chien W. Chang

    2006-01-01

    This paper describes a numerical model developed recently using MATLAB® for performing surface particle coverage calculations. The model uses a multi-bin particle size distribution model with incorporation of Barengoltz's areal density integration method and Raab's particle shape factor, a similar approach employed previously by Ma, Fong and Lee at Lockheed Martin Space Systems Company (Sunnyvale). The developed model is a

  7. Surface functionalized hydrophobic porous particles toward water treatment application.

    PubMed

    Abbaspourrad, Alireza; Carroll, Nick J; Kim, Shin-Hyun; Weitz, David A

    2013-06-18

    A microfluidic-based approach for the fabrication of organic contaminants absorbing core-shell particles is demonstrated. The hydrophobic porous core absorbs oil while the hydrophilic surface enables the particles to be well-dispersed in aqueous solutions. These particles can uptake oil from aqueous solution saturated with oil or via direct contact with oil blobs as depicted in the figure. PMID:23649837

  8. The measurement of boundary layers on a compressor blade in cascade. II - Suction surface boundary layers

    NASA Technical Reports Server (NTRS)

    Deutsch, Steven; Zierke, William C.

    1987-01-01

    A one-component laser Doppler velocimeter (LDV) has been used to measure the two-dimensional, periodic flow field about a double circular arc, compressor blade in cascade. Eleven boundary layer profiles were taken on both the pressure and suction surfaces of the blade, and two were taken in the near wake. In this part of the study, the LDV system is described and the suction surface flow field is documented. The suction surface profiles appear to separate both at the leading edge and again somewhat beyond midchord; the leading edge separation apparently reattaches by 2.6 percent chord.

  9. Dead layer on silicon p-i-n diode charged-particle detectors

    SciTech Connect

    Wall, B. L.; Amsbaugh, John F.; Beglarian, A.; Bergmann, T.; Bichsel, H. C.; Bodine, L. I.; Boyd, N. M.; Burritt, Tom H.; Chaoui, Z.; Corona, T. J.; Doe, Peter J.; Enomoto, S.; Harms, F.; Harper, Gregory; Howe, M. A.; Martin, E. L.; Parno, D. S.; Peterson, David; Petzold, Linda; Renschler, R.; Robertson, R. G. H.; Schwarz, J.; Steidl, M.; Van Wechel, T. D.; VanDevender, Brent A.; Wustling, S.; Wierman, K. J.; Wilkerson, J. F.

    2014-04-21

    Abstract Semiconductor detectors in general have a dead layer at their surfaces that is either a result of natural or induced passivation, or is formed during the process of making a contact. Charged particles passing through this region produce ionization that is incompletely collected and recorded, which leads to departures from the ideal in both energy deposition and resolution. The silicon p-i-n diode used in the KATRIN neutrinomass experiment has such a dead layer. We have constructed a detailed Monte Carlo model for the passage of electrons from vacuum into a silicon detector, and compared the measured energy spectra to the predicted ones for a range of energies from 12 to 20 keV. The comparison provides experimental evidence that a substantial fraction of the ionization produced in the "dead" layer evidently escapes by discussion, with 46% being collected in the depletion zone and the balance being neutralized at the contact or by bulk recombination. The most elementary model of a thinner dead layer from which no charge is collected is strongly disfavored.

  10. Dead layer on silicon p-i-n diode charged-particle detectors

    E-print Network

    B. L. Wall; J. F. Amsbaugh; A. Beglarian; T. Bergmann; H. C. Bichsel; L. I. Bodine; N. M. Boyd; T. H. Burritt; Z. Chaoui; T. J. Corona; P. J. Doe; S. Enomoto; F. Harms; G. C. Harper; M. A. Howe; E. L. Martin; D. S. Parno; D. A. Peterson; L. Petzold; P. Renschler; R. G. H. Robertson; J. Schwarz; M. Steidl; T. D. Van Wechel; B. A. VanDevender; S. Wüstling; K. J. Wierman; J. F. Wilkerson

    2013-10-07

    Semiconductor detectors in general have a dead layer at their surfaces that is either a result of natural or induced passivation, or is formed during the process of making a contact. Charged particles passing through this region produce ionization that is incompletely collected and recorded, which leads to departures from the ideal in both energy deposition and resolution. The silicon \\textit{p-i-n} diode used in the KATRIN neutrino-mass experiment has such a dead layer. We have constructed a detailed Monte Carlo model for the passage of electrons from vacuum into a silicon detector, and compared the measured energy spectra to the predicted ones for a range of energies from 12 to 20 keV. The comparison provides experimental evidence that a substantial fraction of the ionization produced in the "dead" layer evidently escapes by diffusion, with 46% being collected in the depletion zone and the balance being neutralized at the contact or by bulk recombination. The most elementary model of a thinner dead layer from which no charge is collected is strongly disfavored.

  11. Medical applications of diamond particles and surfaces.

    SciTech Connect

    Narayan, R. J.; Boehm, R. D.; Sumant, A. V. (Center for Nanoscale Materials); (Univ. of California)

    2011-04-01

    Diamond has been considered for use in several medical applications due to its unique mechanical, chemical, optical, and biological properties. In this paper, methods for preparing synthetic diamond surfaces and particles are described. In addition, recent developments involving the use of diamond in prostheses, sensing, imaging, and drug delivery applications are reviewed. These developments suggest that diamond-containing structures will provide significant improvements in the diagnosis and treatment of medical conditions over the coming years. Diamond is an allotrope of carbon that is being considered for use in several medical applications. Ramachandran determined that the crystal structure of diamond consists of two close packed interpenetrating face centered cubic lattices; one lattice is shifted with respect to the other along the elemental cube space diagonal by one-quarter of its length. If one approximates carbon atoms as equal diameter rigid spheres, the filling of this construction is 34%. Due to the carbon-carbon distance (1.54 {angstrom}), diamond crystal exhibits the highest atomic density (1.76 x 10{sup 23} cm{sup -3}) of any solid. The very high bond energy between two carbon atoms (83 kcal/mol) and the directionality of tetrahedral bonds are the main reasons for the high strength of diamond. Diamond demonstrates the highest Vickers hardness value of any material (10,000 kg/mm{sup 2}). The tribological properties of diamond are also impressive; the coefficient of friction of polished diamond is 0.07 in argon and 0.05 in humid air. Diamond is resistant to corrosion except in an oxygen atmosphere at temperatures over 800 C. In addition, type IIa diamond exhibits the highest thermal conductivity of all materials (20 W cm{sup -1} K{sup -1} at room temperature).

  12. Growth of the interaction layer around fuel particles in dispersion fuel

    Microsoft Academic Search

    D. Olander

    2009-01-01

    Corrosion of uranium particles in dispersion fuel by the aluminum matrix produces interaction layers (an intermetallic-compound corrosion product) around the shrinking fuel spheres. The rate of this process was modeled as series resistances due to Al diffusion through the interaction layer and reaction of aluminum with uranium in the fuel particle to produce UAlx. The overall kinetics are governed by

  13. Particles in Surface Waters: Coagulation and Transport.

    NASA Astrophysics Data System (ADS)

    Culkin, Gerald William

    Conventional water quality assessment and simulation of particles in natural waters focus on bulk concentrations of the suspended solid phase. These analyses rely directly or indirectly on a linear, 'average particle' approach to describe processes that are nonlinear and highly size -dependent. Size-dependent transport and transformation mechanisms were simulated in this research to identify conditions in which coagulation is important. Explicit finite difference schemes for two-dimensional, laterally-averaged, unsteady particle transport were developed to approximate the size -dependent particle transport processes, which included advection, dispersion, and settling. Coupled exchange of discrete particles between the water column and sediment bed was modeled using size-dependent particle sedimentation and resuspension. Simultaneous particle-particle flocculation was integrated over time in parallel with transport. Model simulations of systems with idealized morphometry and forcing provided greater insight to competing processes that drive particle behavior in natural systems. Application of the model to a real system gave plausible results and suggested explanations for observed conditions.

  14. Multi-orbital Fermi surfaces in metallic layered nickelate

    NASA Astrophysics Data System (ADS)

    Uchida, Masaki; Ishizaka, K.; Sakano, M.; Arita, R.; Shin, S.; Tokura, Y.; Hansmann, P.; Toschi, A.; Held, K.; Yang, X.; Miyawaki, J.; Takata, Y.; Oura, M.; Chainani, A.; Kaneko, Y.; Andersen, O.

    2013-03-01

    The three-dimensional Fermi surface structure of hole-doped metallic layered nickelate Eu2-xSrxNiO4 (x = 1 . 1), an important counterpart to the isostructural superconducting cuprate La2-xSrxCuO4, is investigated by energy-dependent soft-x-ray angle-resolved photoemission spectroscopy. In addition to a large cylindrical hole Fermi surface analogous to the cuprates, we observe a Gamma-centered 3z2 -r2 -derived small electron pocket. This finding demonstrates that in the layered nickelate the 3z2 -r2 band resides close to the x2 -y2 one in energy. The resultant multi-band feature with varying orbital character as revealed may strongly work against the emergence of the high-temperature superconductivity.

  15. On the Effects of Surface Roughness on Boundary Layer Transition

    NASA Technical Reports Server (NTRS)

    Choudhari, Meelan M.; Li, Fei; Chang, Chau-Lyan; Edwards, Jack

    2009-01-01

    Surface roughness can influence laminar-turbulent transition in many different ways. This paper outlines selected analyses performed at the NASA Langley Research Center, ranging in speed from subsonic to hypersonic Mach numbers and highlighting the beneficial as well as adverse roles of the surface roughness in technological applications. The first theme pertains to boundary-layer tripping on the forebody of a hypersonic airbreathing configuration via a spanwise periodic array of trip elements, with the goal of understanding the physical mechanisms underlying roughness-induced transition in a high-speed boundary layer. The effect of an isolated, finite amplitude roughness element on a supersonic boundary layer is considered next. The other set of flow configurations examined herein corresponds to roughness based laminar flow control in subsonic and supersonic swept wing boundary layers. A common theme to all of the above configurations is the need to apply higher fidelity, physics based techniques to develop reliable predictions of roughness effects on laminar-turbulent transition.

  16. Surface layer temperature inversion in the Bay of Bengal

    NASA Astrophysics Data System (ADS)

    Thadathil, Pankajakshan; Gopalakrishna, V. V.; Muraleedharan, P. M.; Reddy, G. V.; Araligidad, Nilesh; Shenoy, Shrikant

    2002-10-01

    Surface layer temperature inversion occurring in the Bay of Bengal has been addressed. Hydrographic data archived in the Indian Oceanographic Data Center are used to understand various aspects of the temperature inversion of surface layer in the Bay of Bengal, such as occurrence time, characteristics, stability, inter-annual variability and generating mechanisms. Spatially organized temperature inversion occurs in the coastal waters of the western and northeastern Bay during winter (November-February). Although the inversion in the northeastern Bay is sustained until February (with remnants seen even in March), in the western Bay it becomes less organized in January and almost disappears by February. Inversion is confined to the fresh water induced seasonal halocline of the surface layer. Inversions of large temperature difference (of the order of 1.6-2.4°C) and thin layer thickness (10-20 m) are located adjacent to major fresh water inputs from the Ganges, Brahmaputra, Irrawaddy, Krishna and Godavari rivers. The inversion is stable with a mean stability of 3600×10 -8 m -1. Inter-annual variability of the inversion is significantly high and it is caused by the inter-annual variability of fresh water flux and surface cooling in the northern Bay. Fresh water flux leads the occurrence process in association with surface heat flux and advection. The leading role of fresh water flux is understood from the observation that the two occurrence regions of inversion (the western and northeastern Bay) have proximity to the two low salinity (with values about 28-29‰) zones. In the western Bay, the East India Coastal Current brings less saline and cold water from the head of the Bay to the south-west Bay, where it advects over warm, saline water, promoting temperature inversion in this region in association with the surface heat loss. For inversion occurring in the northeastern Bay (where the surface water gains heat from atmosphere), surface advection of the less saline cold water from the head of the Bay and Irrawaddy basin is found to be the major causative factor.

  17. Heat rejection to the surface layer of a solar pond

    SciTech Connect

    Jaluria, Y.; Cha, C.K.

    1985-02-01

    An analytical and numerical study of the thermal and fluid flow effects of heat rejection to the surface layer of a salt-gradient solar pond, by means of a recirculating thermal discharge, is carried out. The use of solar ponds for power generation involves heat rejection, for which the surface zone may be employed. However, it is very important to determine the effect of the discharge of hot fluid on the temperature field in the surface zone and on the stability of the nonconvective zone, which lies between the surface and storage zones. Of particular interest is the dependence of this flow on the inflow conditions, on heat loss at the surface and on the inflow-outflow configuration. The downward penetration of the flow is strongly governed by the buoyancy effects, and the study considers both the transient and the steady-state circumstances. The effect of the surface energy loss and of the conductive heat gained from below the surface zone is also studied. The flow is found to be strongly dependent on the inflow and outflow conditions and on the surface heat loss. The disturbance to the nonconvective zone is also studied. The basic physical processes are considered in detail, and the relevance of the results obtained in the design of the corresponding recirculating flow is outlined.

  18. Heat rejection to the surface layer of a solar pond

    SciTech Connect

    Jaluria, Y.; Cha, C.K.

    1983-07-01

    An analytical and numerical study of the thermal and fluid flow effects of heat rejection to the surface layer of a salt-gradient solar pond, using a recirculating thermal discharge, is carried out. The use of solar ponds for power generation involves heat rejection, for which the surface zone may be employed. However, it is very important to determine the effect of the discharge of hot fluid on the temperature field in the surface zone and on the stability of the nonconvective zone, which lies between the surface and storage zones. Of particular interest is the dependence of this flow on the inflow conditions, on heat loss at the surface and on the inflow-outflow configuration. The downward penetration of the flow is governed strongly by the buoyancy effects and the study considers both the transient and the steady-state circumstances. The effect of the surface energy loss and of the conductive heat gained from below the surface zone is also studied. The flow is found to be strongly dependent on the inflow and outflow conditions and on the surface heat loss. The disturbance to the nonconvective zone is also studied. The basic physical processes involved are considered in detail and the relevance of the results obtained in the design of the corresponding recirculating flow is outlined.

  19. Surface-cooling effects on compressible boundary-layer instability

    NASA Technical Reports Server (NTRS)

    Seddougui, Sharon O.; Bowles, R. I.; Smith, F. T.

    1990-01-01

    The influence of surface cooling on compressible boundary layer instability is discussed theoretically for both viscous and inviscid modes, at high Reynolds numbers. The cooling enhances the surface heat transfer and shear stress, creating a high heat transfer sublayer. This has the effect of distorting and accentuating the viscous Tollmien-Schlichting modes to such an extent that their spatial growth rates become comparable with, and can even exceed, the growth rates of inviscid modes, including those found previously. This is for moderate cooling, and it applies at any Mach number. In addition, the moderate cooling destabilizes otherwise stable viscous or inviscid modes, in particular triggering outward-traveling waves at the edge of the boundary layer in the supersonic regime. Severe cooling is also discussed as it brings compressible dynamics directly into play within the viscous sublayer. All the new cooled modes found involve the heat transfer sublayer quite actively, and they are often multi-structured in form and may be distinct from those observed in previous computational and experimental investigations. The corresponding nonlinear processes are also pointed out with regard to transition in the cooled compressible boundary layer. Finally, comparisons with Lysenko and Maslov's (1984) experiments on surface cooling are presented.

  20. Particle image velocimetry measurements of a shock wave\\/turbulent boundary layer interaction

    Microsoft Academic Search

    R. A. Humble; F. Scarano; B. W. van Oudheusden

    2007-01-01

    Particle image velocimetry is used to investigate the interaction between an incident shock wave and a turbulent boundary\\u000a layer at Mach 2.1. A particle response assessment establishes the fidelity of the tracer particles. The undisturbed boundary\\u000a layer is characterized in detail. The mean velocity field of the interaction shows the incident and reflected shock wave pattern,\\u000a as well as the

  1. Impact of small changes in particle surface chemistry for unentangled polymer nanocomposites.

    PubMed

    Ranka, Moulik; Varkey, Nihal; Ramakrishnan, Subramanian; Zukoski, Charles F

    2015-02-28

    We report microstructural and rheological consequences of altering silica particle surface chemistry when the particles are suspended in unentangled polyethylene glycol with a molecular weight of 400. The particle surfaces are altered by reacting them with isobutyltrimethyoxysilane. Levels of silanization are chosen so that the particles remain dispersed in the polymer at all volume fractions studied. Our studies indicate that at the levels studied, silanization does not alter the hydrodynamic thickness of the absorbed polymer layer thickness. Rheological properties are not sensitive to levels of silanization up to particle volume fractions where the average particle separation h ? 6Rg (4.8 nm). At these volume fractions, composite microstructure undergoes changes associated with jamming of soft particles (decorrelations in the first peak of the particle structure factor and the onset of a non-diffusive mechanism that dominates particle density fluctuations at short times.) In the region of volume fractions where h/Rg < 6, the zero-shear rate viscosity of the composites is extremely sensitive to level of silanization with a decrease in the zero-shear rate viscosity by four orders of magnitude observed for the highest levels of silanization studied in comparison to the bare particles. PMID:25600762

  2. Detecting surface roughness effects on the atmospheric boundary layer via AIRSAR data: A field experiment in Death Valley, California

    NASA Technical Reports Server (NTRS)

    Blumberg, Dan G.; Greeley, Ronald

    1992-01-01

    The part of the troposphere influenced by the surface of the earth is termed the atmospheric boundary layer. Flow within this layer is influenced by the roughness of the surface; rougher surfaces induce more turbulence than smoother surfaces and, hence, higher atmospheric transfer rates across the surface. Roughness elements also shield erodible particles, thus decreasing the transport of windblown particles. Therefore, the aerodynamic roughness length (z(sub 0)) is an important parameter in aeolian and atmospheric boundary layer processes as it describes the aerodynamic properties of the underlying surface. z(sub 0) is assumed to be independent of wind velocity or height, and dependent only on the surface topography. It is determined using in situ measurements of the wind speed distribution as a function of height. For dry, unvegetated soils the intensity of the radar backscatter (sigma(sup 0)) is affected primarily by surface roughness at a scale comparable with the radar wavelength. Thus, both wind and radar respond to surface roughness variations on a scale of a few meters or less. Greeley showed the existence of a correlation between z(sub 0) and sigma(sup 0). This correlation was based on measurements over lava flows, alluvial fans, and playas in the southwest deserts of the United States. It is shown that the two parameters behave similarly also when there are small changes over a relatively homogeneous surface.

  3. Tape method of forming a thin layer of doped lanthanum chromite particles and of bonding such on an electrode

    DOEpatents

    Richards, V.L.; Singhal, S.C.; Pal, U.B.

    1992-07-21

    A combustible polymer film, useful for application of an interconnection on an electrode is made by: (1) providing doped LaCro[sub 3] particles; (2) dispersing doped LaCrO[sub 3] particles in a solvent, to provide a dispersion; (3) screening the dispersion to provide particles in the range of from 30 micrometers to 80 micrometers; (4) admixing a fugitive polymer with the particles; (5) casting the dispersion to provide a film; (6) drying the film; and (7) stripping the film. The film can then be applied to a porous, preheated electrode top surface, and then a dense skeletal LaCrO[sub 3] structure is electrochemically vapor deposited between and around the doped LaCrO[sub 3] particles. Additional solid oxide electrolyte and fuel electrode layers can then be added to provide a fuel cell. 4 figs.

  4. DNS of Oscillatory Boundary Layer Over a Closely Packed Layer of Sediment Particles

    NASA Astrophysics Data System (ADS)

    Ghodke, Chaitanya D.; Skitka, Joseph; Apte, Sourabh V.

    2013-11-01

    Fully resolved direct numerical simulations are performed using fictitious domain approach (Apte et al., JCP 2009) to investigate oscillatory turbulent flow over a rough wall corresponding to the experimental work of Keiller & Sleath (JFM 1976) and representative of a sediment layer in coastal environments. Four particle Reynolds numbers in the range, Re = 660 - 2780 are studied for a fixed sphere size and results are compared against available experimental data. Flow is characterized in terms of coherent vortex structures, Reynolds stress variation, turbulent cross-correlations and PDF distributions. Reynolds stress is negative during the first half of the cycle as ejection and sweep events prevail and is positive during the second half where outward/inward interactions of motion are dominant. The net lift coefficient remains positive over the cycle with a period which is half of that of the forcing function and is well correlated with phase averaged velocity square (U2). The pressure contribution towards the net lift force is found to be more dominant over the viscous contribution. Also the PDF distributions of velocity fluctuations show non-Gaussian behavior. These detailed findings are useful in improving the criterion for predicting sediment incipient motion. Fully resolved direct numerical simulations are performed using fictitious domain approach (Apte et al., JCP 2009) to investigate oscillatory turbulent flow over a rough wall corresponding to the experimental work of Keiller & Sleath (JFM 1976) and representative of a sediment layer in coastal environments. Four particle Reynolds numbers in the range, Re = 660 - 2780 are studied for a fixed sphere size and results are compared against available experimental data. Flow is characterized in terms of coherent vortex structures, Reynolds stress variation, turbulent cross-correlations and PDF distributions. Reynolds stress is negative during the first half of the cycle as ejection and sweep events prevail and is positive during the second half where outward/inward interactions of motion are dominant. The net lift coefficient remains positive over the cycle with a period which is half of that of the forcing function and is well correlated with phase averaged velocity square (U2). The pressure contribution towards the net lift force is found to be more dominant over the viscous contribution. Also the PDF distributions of velocity fluctuations show non-Gaussian behavior. These detailed findings are useful in improving the criterion for predicting sediment incipient motion. NSF project #1133363, Sediment-Bed-Turbulence Coupling in Oscillatory Flows.

  5. A novel surface cleaning method for chemical removal of fouling lead layer from chromium surfaces

    NASA Astrophysics Data System (ADS)

    Gholivand, Kh.; Khosravi, M.; Hosseini, S. G.; Fathollahi, M.

    2010-10-01

    Most products especially metallic surfaces require cleaning treatment to remove surface contaminations that remain after processing or usage. Lead fouling is a general problem which arises from lead fouling on the chromium surfaces of bores and other interior parts of systems which have interaction with metallic lead in high temperatures and pressures. In this study, a novel chemical solution was introduced as a cleaner reagent for removing metallic lead pollution, as a fouling metal, from chromium surfaces. The cleaner aqueous solution contains hydrogen peroxide (H 2O 2) as oxidizing agent of lead layer on the chromium surface and acetic acid (CH 3COOH) as chelating agent of lead ions. The effect of some experimental parameters such as acetic acid concentration, hydrogen peroxide concentration and temperature of the cleaner solution during the operation on the efficiency of lead cleaning procedure was investigated. The results of scanning electron microscopy (SEM) showed that using this procedure, the lead pollution layer could be completely removed from real chromium surfaces without corrosion of the original surface. Finally, the optimum conditions for the complete and fast removing of lead pollution layer from chromium surfaces were proposed. The experimental results showed that at the optimum condition (acetic acid concentration 28% (V/V), hydrogen peroxide 8% (V/V) and temperature 35 °C), only 15-min time is needed for complete removal of 3 g fouling lead from a chromium surface.

  6. Low-order representations of irregular surface roughness and their impact on a turbulent boundary layer

    NASA Astrophysics Data System (ADS)

    Mejia-Alvarez, R.; Christensen, K. T.

    2010-01-01

    The present effort explores the relative impact of various topographical scales present within irregular surface roughness on a turbulent boundary layer under both developing- and developed-flow conditions. Low-order representations of highly irregular surface roughness replicated from a turbine-blade damaged by deposition of foreign materials were generated using singular value decomposition to decompose the complex topography into a set of topographical basis functions of decreasing importance to the original ("full") surface character. The low-order surface models were then formed by truncating the full set of basis functions at the first 5 and 16 modes (containing approximately 71% and 95% of the full surface content, respectively) so that only the most dominant and large-scale topographical features were included in the models, while the finer-scale surface details are excluded. Physical replications of the full surface and the two low-order models were created using rapid prototyping methods to generate short and long streamwise fetches of roughness, and particle-image velocimetry was used to acquire ensembles of instantaneous velocity fields in the streamwise-wall-normal plane for developing- and developed-flow conditions at moderate Reynolds number. Comparison of both single- and multipoint statistics (mean velocity and Reynolds normal and shear stresses) as well as quadrant analysis of the instantaneous events contributing to the mean Reynolds shear stress indicates that a 16-mode model of the full surface faithfully reproduces the characteristics of flow over the full surface for both developing- and developed-flow conditions. For the latter scenario, both the 5- and 16-mode models reproduce the outer-layer characteristics for flow over the full surface in accordance with Townsend's wall similarity hypothesis. However, neither low-order surface representation fully reproduces important details of the Reynolds-shear-stress-producing events within the roughness sublayer, particularly the contributions of the most intense ejection and sweep events.

  7. Calibration of charge state conversion surfaces for neutral particle detectors

    SciTech Connect

    Wahlstroem, P.; Scheer, J. A.; Wurz, P. [Physikalisches Institut, University of Bern, Sidlerstrasse 5, 3012 Bern (Switzerland); Hertzberg, E.; Fuselier, S. A. [Lockheed Martin Advanced Technology Center, 3251 Hanover St., Palo Alto, California 94304 (United States)

    2008-08-01

    Molecular oxygen and hydrogen ions were scattered off hydrogen terminated diamondlike carbon (DLC) charge state conversion surfaces at incident grazing angles. The energy range of the scattered particles was 390-1000 eV, and the surface roughness of the DLC surface was of the order of 1 A rms. For all surfaces almost equal angular scattering and negative ion fractions were found within the uncertainties of the measurement. This result supports the fact that charge state conversion with DLC surfaces is a reliable technology for neutral particle sensing instruments. Furthermore, these instruments can work in the laboratory as well as in the harsh environment on board a satellite.The surfaces measured here are used in the IBEX-lo sensor, a neutral particle sensing instrument on the NASA IBEX mission, which is scheduled for launch into orbit around Earth in July 2008.

  8. Financial Brownian particle in the layered order-book fluid and fluctuation-dissipation relations.

    PubMed

    Yura, Yoshihiro; Takayasu, Hideki; Sornette, Didier; Takayasu, Misako

    2014-03-01

    We introduce a novel description of the dynamics of the order book of financial markets as that of an effective colloidal Brownian particle embedded in fluid particles. The analysis of comprehensive market data enables us to identify all motions of the fluid particles. Correlations between the motions of the Brownian particle and its surrounding fluid particles reflect specific layering interactions; in the inner layer the correlation is strong and with short memory, while in the outer layer it is weaker and with long memory. By interpreting and estimating the contribution from the outer layer as a drag resistance, we demonstrate the validity of the fluctuation-dissipation relation in this nonmaterial Brownian motion process. PMID:24655287

  9. Financial Brownian particle in the layered order book fluid and Fluctuation-Dissipation relations

    E-print Network

    Yura, Yoshihiro; Sornette, Didier; Takayasu, Misako

    2014-01-01

    We introduce a novel description of the dynamics of the order book of financial markets as that of an effective colloidal Brownian particle embedded in fluid particles. The analysis of a comprehensive market data enables us to identify all motions of the fluid particles. Correlations between the motions of the Brownian particle and its surrounding fluid particles reflect specific layering interactions; in the inner-layer, the correlation is strong and with short memory while, in the outer-layer, it is weaker and with long memory. By interpreting and estimating the contribution from the outer-layer as a drag resistance, we demonstrate the validity of the fluctuation-dissipation relation (FDR) in this non-material Brownian motion process.

  10. 45S5 Bioactive glass surface charge variations and the formation of a surface calcium phosphate layer in a

    E-print Network

    Lu, Helen H.

    45S5 Bioactive glass surface charge variations and the formation of a surface calcium phosphate: bioactivity; surface charge; fibronectin; protein adsorption; calcium phosphate layer INTRODUCTION By forming a surface calcium phosphate layer in vivo, bioactive materials, such as 45S5 bioactive glass (BG), are able

  11. Assembled monolayers of hydrophilic particles on water surfaces.

    PubMed

    Moon, Geon Dae; Lee, Tae Il; Kim, Bongsoo; Chae, GeeSung; Kim, Jinook; Kim, SungHee; Myoung, Jae-Min; Jeong, Unyong

    2011-11-22

    A facile and quick approach to prepare self-assembled monolayers of water-dispersible particles on the water surface is presented. Particle suspensions in alcohols were dropped on a water reservoir to form long-range ordered monolayers of various particles, including spherical solid particles, soft hydrogel particles, metal nanoparticles, quantum dots, nanowires, single-wall carbon nanotubes (SWCNTs), nanoplates, and nanosheets. A systematic study was conducted on the variables affecting the monolayer assembly: the solubility parameter of spreading solvents, particle concentration, zeta potential of the particles in the suspension, surface tension of the water phase, hardness of the particles, and addition of a salt in the suspension. This method requires no hydrophobic surface treatment of the particles, which is useful to exploit these monolayer films without changing the native properties of the particles. The study highlights a quick 2D colloidal assembly without cracks in the wafer scale as well as transparent conductive thin films made of SWCNTs and graphenes. PMID:21962177

  12. Tribological Properties of Aluminum Alloy treated by Fine Particle Peening/DLC Hybrid Surface Modification

    NASA Astrophysics Data System (ADS)

    Amano, Y.; Nanbu, H.; Kameyama, Y.; Komotori, J.

    2010-06-01

    In order to improve the adhesiveness of the DLC coating, Fine Particle Peening (FPP) treatment was employed as pre-treatment of the DLC coating process. FPP treatment was performed using SiC shot particles, and then AA6061-T6 aluminum alloy was DLC-coated. A SiC-rich layer was formed around the surface of the aluminum alloy by the FPP treatment because small chips of shot particles were embedded into the substrate surface. Reciprocating sliding tests were conducted to measure the friction coefficients. While the DLC coated specimen without FPP treatment showed a sudden increase in friction coefficient at the early stage of the wear cycles, the FPP/DLC hybrid treated specimen maintained a low friction coefficient value during the test period. Further investigation revealed that the tribological properties of the substrate after the DLC coating were improved with an increase in the amount of Si at the surface.

  13. Effects of nanoparticle layering on nanofluid and base fluid pool boiling heat transfer from a horizontal surface under atmospheric pressure

    NASA Astrophysics Data System (ADS)

    White, Steven B.; Shih, Albert J.; Pipe, Kevin P.

    2010-06-01

    Previous heat transfer studies of nanofluids have shown that suspended nanoparticles can affect thermal properties within a fluid and furthermore can affect surface roughness by depositing on a heater surface. Pool boiling studies of nanofluids have demonstrated either enhanced or diminished heat transfer, yet have been unable to distinguish the contributions of increased surface roughness and suppression of bubble transport by suspended particles because they have used base fluids on a clean boiling surface as a comparison. We resolve this uncertainty by studying the boiling performance of a surface exposed to a series of boiling tests that alternate between water and a water-based nanofluid with suspended 40 nm ZnO nanoparticles. We find that the performance for the water tests increases significantly, showing a 62% enhancement after four cycles. This increase correlates well with a surface roughness model for boiling that uses atomic force microscopy-measured surface data to quantify the layering of nanoparticles in intervening nanofluid boiling tests. We find that the performance of the ZnO nanofluid initially shows a 24% enhancement versus water on a clean (unroughened) surface, but then steadily declines in later tests as nanoparticle layering occurs, showing a measured trend that is opposite that of water. We ascribe this decrease to the suppression of bubble formation and motion by the suspended particles. The results demonstrate that the effect of increased surface roughness due to nanoparticle layering can be twofold, greatly enhancing boiling for the base fluid and slightly decreasing performance for the nanofluid.

  14. A novel particle assembly template using plasma surface modification and self-assembly monolayer for nano\\/micro patterns

    Microsoft Academic Search

    Wang-Shen Su; Weileun Fang; Ming-Shih Tsai

    2005-01-01

    A novel self-assembly method of particles on the specific hydrophilic pattern regions to fabricate nano\\/micro patterns has been investigated in this study. The surface hydrophilicity modification is employed to tune the contact angle of droplet. Control of surface energy was investigated in this study for finely tuning the shape and layer number of particles assembly. The micro\\/nano patterns formed by

  15. Particle adhesion to surfaces under vacuum

    NASA Technical Reports Server (NTRS)

    Barengoltz, Jack B.

    1988-01-01

    The release of glass beads and standard dust from aluminum and glass substrates under centrifugation (simulating atmospheric pressure, low vacuum, and high vacuum conditions) was measured, with application to the estimation of contaminant particle release during spacecraft launch. For particles in the 10-100 micron range, dust was found to adhere more strongly than glass beads in all the cases considered. For most of the cases, dust and glass beads adhered more strongly to glass than to aluminum at all pressures. The adhesion force for dust on glass at 10 torr was shown to be as small as the value for dust on aluminum.

  16. Atmospheric surface and boundary layers of the Amazon Basin

    NASA Technical Reports Server (NTRS)

    Garstang, Michael

    1987-01-01

    Three phases of work were performed: design of and preparation for the Amazon Boundary Layer Experiment (ABLE 2-A); execution of the ABLE 2-A field program; and analysis of the ABLE 2-A data. Three areas of experiment design were dealt with: surface based meteorological measurements; aircraft missions; and project meteorological support. The primary goal was to obtain a good description of the structure of the atmosphere immediately above the rain forest canopy (top of canopy to a few thousand meters), to describe this region during the growing daytime phase of the boundary layer; and to examine the nighttime stratified state. A secondary objective was to examine the role that deep convective storms play in the vertical transport of heat, water vapor, and other trace gases. While significant progress was made, much of the analysis remains to be done.

  17. Simultaneous detection of separation and transition in surface shear layers

    NASA Astrophysics Data System (ADS)

    Mangalam, Siva M.; Stack, J. P.; Sewall, W. G.

    1989-04-01

    Flush-mounted hot-film gages have proved effective in detecting boundary-layer transition and in measuring skin friction but with limited success in detecting laminar separation and reattachment. The development of multielement micro hot-film sensors, and the recent discovery of the phase reversal phenomena associated with low-frequency dynamic shear stress signals across regions of laminar separation and turbulent reattachment, have made it possible to simultaneously and unambiguously detect these surface shear layer characteristics. Experiments were conducted on different airfoils at speeds ranging from low subsonic to transonic speeds to establish the technique for incompressible and compressible flow applications. The multielement dynamic shear stress sensor technique was successfully used to detect laminar separation, turbulent reattachment, as well as, shock induced laminar and turbulent separation.

  18. Quantitative layer analysis of single crystal surfaces by LEIS

    NASA Astrophysics Data System (ADS)

    Beikler, Robert; Taglauer, Edmund

    2002-06-01

    The quantitative interpretation of energy and angle resolved low-energy ion scattering intensity distributions is achieved by comparing the experimental results with those from numerical simulations using the MARLOWE code with extensions for layer selective analysis. The example used is the CuAu(1 0 0) alloy crystal surface. For adequate analysis the potential parameter (i.e. the screening length) has to be calibrated. This is done by using elemental single crystal standards. Anisotropic thermal vibrations are taken into account in correspondence with published Debye temperature values. Neutralization effects are found to be of minor importance for Na + and He + scattering from CuAu. A quantitative analysis of the first and second layer composition of CuAu(1 0 0) as a function of temperature could thus be obtained, the results being in good agreement with theoretical predictions.

  19. Shape-selective sieving layers on an oxide catalyst surface

    NASA Astrophysics Data System (ADS)

    Canlas, Christian P.; Lu, Junling; Ray, Natalie A.; Grosso-Giordano, Nicolas A.; Lee, Sungsik; Elam, Jeffrey W.; Winans, Randall E.; van Duyne, Richard P.; Stair, Peter C.; Notestein, Justin M.

    2012-12-01

    New porous materials such as zeolites, metal-organic frameworks and mesostructured oxides are of immense practical utility for gas storage, separations and heterogeneous catalysis. Their extended pore structures enable selective uptake of molecules or can modify the product selectivity (regioselectivity or enantioselectivity) of catalyst sites contained within. However, diffusion within pores can be problematic for biomass and fine chemicals, and not all catalyst classes can be readily synthesized with pores of the correct dimensions. Here, we present a novel approach that adds reactant selectivity to existing, non-porous oxide catalysts by first grafting the catalyst particles with single-molecule sacrificial templates, then partially overcoating the catalyst with a second oxide through atomic layer deposition. This technique is used to create sieving layers of Al2O3 (thickness, 0.4-0.7 nm) with ‘nanocavities’ (<2 nm in diameter) on a TiO2 photocatalyst. The additional layers result in selectivity (up to 9:1) towards less hindered reactants in otherwise unselective, competitive photocatalytic oxidations and transfer hydrogenations.

  20. Patterning surfaces with colloidal particles using optical tweezers

    NASA Astrophysics Data System (ADS)

    Hoogenboom, J. P.; Vossen, D. L. J.; Faivre-Moskalenko, C.; Dogterom, M.; van Blaaderen, A.

    2002-06-01

    A method for positioning colloidal particles on surfaces in any designed pattern is described. Optical tweezers are used to bring particles from a reservoir to the substrate where opposite surface charges are used to immobilize particles on the surface. Both chemical surface modification and polyelectrolyte coating of either substrate or colloids make the method generally applicable. We show that using this technique large, two-dimensional patterns can be created that can be dried without distortions by critical point drying. As an example we show the positioning of 79 nm radius metallodielectric particles and we show how two-dimensional patterns can be used to direct three-dimensional epitaxial crystal growth. The method is inexpensive, relatively fast, and can be fully automated.

  1. Resonance line shapes and catastrophes in particle-surface scattering

    NASA Astrophysics Data System (ADS)

    Margalef-Roig, J.; Miret-Artés, S.

    2001-03-01

    In this work we present a general study of resonance line shapes within the catastrophe theory framework and valid for any type of scattering: particle-particle, particle-surface, or liquid and light-particle. The standard profiles analyzed, and issued from the multichannel scattering theory, correspond to isolated Fano-type, double, critical, and dipole resonances. They have been topologically classified according to the well-known elementary catastrophes: fold, cusp, and its dual and swallowtail, respectively. The onset of each structural change, or topological transition, at some external, critical parameter value, like the surface temperature, is discussed in terms of the probabilities of entering and leaving the resonance as well as of the direct scattering. Finally, atom-surface scattering is studied in more detail showing that the critical temperature is very close to the Debye surface temperature.

  2. Assessment of fluorescent particles for surface flow analysis.

    PubMed

    Tauro, Flavia; Mocio, Gabriele; Rapiti, Emiliano; Grimaldi, Salvatore; Porfiri, Maurizio

    2012-01-01

    In this paper, a systematic performance assessment of the measurement system for surface flow analysis developed by our group in (Tauro et al., Sensors, 2010) is presented. The system is based on the detection of buoyant fluorescent microspheres through a low-cost apparatus, which incorporates light sources to elicit fluorescence response and a digital camera to identify the particles' transit. Experiments are conducted using green fluorescent particles and further tests are executed to evaluate the system performance for red and orange particles varying in emission wavelength, degree of biocompatibility, and cost. The influence of the following parameters on surface flow sensing using fluorescent beads is investigated: (i) distance of the light sources from the water surface, (ii) presence of an ad-hoc filter tuned at the particle emission wavelength, (iii) camera resolution and frame rate, (iv) flow regime, and (v) ambient light. Experimental results are used to inform implementation guidelines for surface flow analysis in natural environments. PMID:23202234

  3. Assessment of Fluorescent Particles for Surface Flow Analysis

    PubMed Central

    Tauro, Flavia; Mocio, Gabriele; Rapiti, Emiliano; Grimaldi, Salvatore; Porfiri, Maurizio

    2012-01-01

    In this paper, a systematic performance assessment of the measurement system for surface flow analysis developed by our group in (Tauro et al., Sensors, 2010) is presented. The system is based on the detection of buoyant fluorescent microspheres through a low-cost apparatus, which incorporates light sources to elicit fluorescence response and a digital camera to identify the particles' transit. Experiments are conducted using green fluorescent particles and further tests are executed to evaluate the system performance for red and orange particles varying in emission wavelength, degree of biocompatibility, and cost. The influence of the following parameters on surface flow sensing using fluorescent beads is investigated: (i) distance of the light sources from the water surface, (ii) presence of an ad-hoc filter tuned at the particle emission wavelength, (iii) camera resolution and frame rate, (iv) flow regime, and (v) ambient light. Experimental results are used to inform implementation guidelines for surface flow analysis in natural environments. PMID:23202234

  4. Surface modification of polypropylene based particle foams

    NASA Astrophysics Data System (ADS)

    Schreier, P.; Trassl, C.; Altstädt, V.

    2014-05-01

    This paper deals with the modification of the surface properties of expanded polypropylene (EPP). EPP is a semi-hard to soft elastic thermoplastic foam. The characteristic surface of EPP shows process-related steam nozzle imprints and gussets. Therefore EPP does not satisfy the quality requirements for visible automotive applications. In order to meet these demands, plastic surfaces are usually enhanced with functional or decorative coatings, e.g. textiles, plastic films or paint. The coating of plastics with low surface energies such as PP often leads to adhesion problems by reason of the missing polar and functional groups. This paper gives an evaluation of activation and pre-treatment methods of EPP, with the aim to identify the most suitable pre-treatment method. For this purpose five typical surface treatment methods - flame treatment, corona, fluorination, atmospheric and low-pressure plasma - were performed on EPP samples. As a comparison criterion the maximum increase in the adhesion force between a polyurethane-based coating and the modified EPP substrate was selected. Moreover the influence of the selected pre-treatment method on the increase in the total surface energy and its polar component was investigated by the drop shape analysis method. The results showed that the contact angle measurement is a suitable method to determine the polar and disperse fractions of the surface tension of EPP. Furthermore, all performed methods increased the adhesion of EPP.

  5. Analysing the Properties of Surface Layers Generated by Sheet Metal Forming Operations

    NASA Astrophysics Data System (ADS)

    Šugárová, Jana; Šugár, Peter; Zemko, Peter

    2010-01-01

    The paper brings results of the surface layers properties analysis of a thin wall hollow sheet metal parts, produced by metal spinning and deep drawing. The influence of mandrel (workpiece) frequency of rotation on the spun parts surface layer strainhardening is studied and compared with the quality of the formed part surface layer produced by deep drawing technology.

  6. Fabrication of nonaging superhydrophobic surfaces by packing flowerlike hematite particles

    Microsoft Academic Search

    Anmin Cao; Liangliang Cao; Di Gao

    2007-01-01

    The authors demonstrate the fabrication of nonaging superhydrophobic surfaces by packing flowerlike micrometer-sized hematite (alpha-Fe2O3) particles. Although hematite is intrinsically hydrophilic, the nanometer-sized protrusions on the particles form textures with overhanging structures that prevent water from entering into the textures and induce a macroscopic superhydrophobic phenomenon. These superhydrophobic surfaces do not age even in extremely oxidative environments-they retain the superhydrophobicity

  7. Synthesis and surface chemistry of nano silver particles

    Microsoft Academic Search

    Revathi Janardhanan; Murugan Karuppaiah; Neha Hebalkar; Tata Narsinga Rao

    2009-01-01

    In this report, we present a simple wet chemical route to synthesize nano-sized silver particles, and their surface properties are discussed in detail. Silver nano particles of the size 40–80nm are formed in the process of oxidation of glucose to gluconic acid by amine in the presence of silver nitrate, and the gluconic acid caps the nano silver particle. The

  8. Plasma-enhanced deposition of antifouling layers on silicone rubber surfaces

    NASA Astrophysics Data System (ADS)

    Jiang, Hongquan

    In food processing and medical environments, biofilms serve as potential sources of contamination, and lead to food spoilage, transmission of diseases or infections. Because of its ubiquitous and recalcitrant nature, Listeria monocytogenes biofilm is especially hard to control. Generating antimicrobial surfaces provide a method to control the bacterial attachment. The difficulty of silver deposition on polymeric surfaces has been overcome by using a unique two-step plasma-mediated method. First silicone rubber surfaces were plasma-functionalized to generate aldehyde groups. Then thin silver layers were deposited onto the functionalized surfaces according to Tollen's reaction. X-ray photoelectron spectroscopy (XPS), atomic force spectroscopy (AFM) and scanning electron microscopy (SEM) showed that silver particles were deposited. By exposing the silver coated surfaces to L. monocytogenes, it was demonstrated that they were bactericidal to L. monocytogenes. No viable bacteria were detected after 12 to 18 h on silver-coated silicone rubber surfaces. Another antifouling approach is to generate polyethylene glycol (PEG) thin layer instead of silver on polymer surfaces. Covalent bond of PEG structures of various molecular weights to cold-plasma-functionalized polymer surfaces, such as silicone rubber, opens up a novel way for the generation of PEG brush-like or PEG branch-like anti-fouling layers. In this study, plasma-generated surface free radicals can react efficiently with dichlorosilane right after plasma treatment. With the generation of halo-silane groups, this enables PEG molecules to be grafted onto the modified surfaces. XPS data clearly demonstrated the presence of PEG molecules on plasma-functionalized silicone rubber surfaces. AFM images showed the changed surface morphologies as a result of covalent attachment to the surface of PEG molecules. Biofilm experiment results suggest that the PEG brush-like films have the potential ability to be the next generation antifouling deposition. However, the coverage on FSR needs to be improved. Different PEG structures (brush, branched, oxirane-group terminated and PEG terminated structures) were developed in this study to understand the bacterial attachment behavior and the antifouling mechanism of PEG-like structures. Results from biofilm experiments demonstrated the absence of antifouling behavior. The presence of PEG structure on substrate surfaces cannot guarantee antifouling ability.

  9. CORRELATIVE SURFACE ANALYSIS STUDIES OF ENVIRONMENTAL PARTICLES

    EPA Science Inventory

    Various surface analysis techniques (scanning electron microscopy/energy dispersive X-ray microanalysis (SEM/EDX), electron spectroscopy for chemical analysis (ESCA), and secondary ion mass spectrometry (SIMS) were evaluated in a correlative regimen for the chemical characterizat...

  10. The characteristic averaging time for the surface-layer fluxes

    NASA Astrophysics Data System (ADS)

    Calaf, M.; Iungo, V.; Oldroyd, H. J.; Giometto, M. G.; Parlange, M. B.

    2014-12-01

    The choice of the representative averaging time to compute surface-layer fluxes remains a source of discrepancy between studies. While the Ogive function (Oncley et al. 1996) has become the standard approach to determine the 'physically sound' averaging time, uncertainty remains on how to precisely select the minimum-necessary averaging time. Alternatives based on a multiresolution analysis exist and they can further provide a characteristic time-scale separating turbulence from mesoscale motions (Vickers and Mahrt, 2003, 2005). Yet little is learned from the inherent turbulent time scales and their corresponding contribution to the overall surface-layer fluxes. Here a new approach based on a Proper Orthogonal Decomposition (POD) will be presented, where the extracted characteristic averaging times are energy optimal. Consequently one can now select from these POD-provided characteristic times, the most relevant time scales depending on the desired application and based on the overall energy contribution to the surface-layer fluxes. One of the main advantages of the POD-technique compared to traditional Fourier analysis or wavelet decompositions is that the shape of the eigenfunctions is directly dictated by the input data and that the resultant eigenfunctions are energy ordered in the most optimal sense. Thus, one can really determine a-priori the most 'physically relevant' averaging time without source of ambiguity. Examples of the proposed approach in varied complex scenarios will be presented, spanning multiple atmospheric stratifications and topography driven flows. Further, results exploring the potential of the POD technique to determine the proper averaging times for tilt corrections will also be presented.

  11. Homogenous Surface Nucleation of Solid Polar Stratospheric Cloud Particles

    NASA Technical Reports Server (NTRS)

    Tabazadeh, A.; Hamill, P.; Salcedo, D.; Gore, Warren J. (Technical Monitor)

    2002-01-01

    A general surface nucleation rate theory is presented for the homogeneous freezing of crystalline germs on the surfaces of aqueous particles. While nucleation rates in a standard classical homogeneous freezing rate theory scale with volume, the rates in a surface-based theory scale with surface area. The theory is used to convert volume-based information on laboratory freezing rates (in units of cu cm, seconds) of nitric acid trihydrate (NAT) and nitric acid dihydrate (NAD) aerosols into surface-based values (in units of sq cm, seconds). We show that a surface-based model is capable of reproducing measured nucleation rates of NAT and NAD aerosols from concentrated aqueous HNO3 solutions in the temperature range of 165 to 205 K. Laboratory measured nucleation rates are used to derive free energies for NAT and NAD germ formation in the stratosphere. NAD germ free energies range from about 23 to 26 kcal mole, allowing for fast and efficient homogeneous NAD particle production in the stratosphere. However, NAT germ formation energies are large (greater than 26 kcal mole) enough to prevent efficient NAT particle production in the stratosphere. We show that the atmospheric NAD particle production rates based on the surface rate theory are roughly 2 orders of magnitude larger than those obtained from a standard volume-based rate theory. Atmospheric volume and surface production of NAD particles will nearly cease in the stratosphere when denitrification in the air exceeds 40 and 78%, respectively. We show that a surface-based (volume-based) homogeneous freezing rate theory gives particle production rates, which are (not) consistent with both laboratory and atmospheric data on the nucleation of solid polar stratospheric cloud particles.

  12. Particle concentrations and number size distributions in the planetary boundary layer derived from airship based measurements

    NASA Astrophysics Data System (ADS)

    Tillmann, Ralf; Zhao, Defeng; Ehn, Mikael; Hofzumahaus, Andreas; Holland, Frank; Rohrer, Franz; Kiendler-Scharr, Astrid; Wahner, Andreas

    2014-05-01

    Atmospheric particles play a key role for regional and global climate due to their direct and indirect radiative forcing effects. The concentration and size of the particles are important variables to these effects. Within the continental planetary boundary layer (PBL) the particle number size distribution is influenced by meteorological parameters, local sinks and sources resulting in variable spatial distributions. However, measurements of particle number size distributions over a broad vertical range of the PBL are rare. The airship ZEPPELIN NT is an ideal platform to measure atmospheric aerosols on a regional scale within an altitude range up to 1000 m. For campaigns in the Netherlands, Northern Italy and South Finland in 2012 and 2013 the airship was deployed with a wide range of instruments, including measurements of different trace gases, short lived radicals, solar radiation, aerosols and meteorological parameters. Flights were carried out at different times of the day to investigate the influence of the diurnal evolution of the PBL on atmospheric trace gases and aerosols. During night and early morning hours the concentration and size distribution of atmospheric particles were found to be strongly influenced by the layered structure of the PBL, i.e. the nocturnal boundary layer and the residual layer. Within the residual layer particle concentrations stay relatively constant as this layer is decoupled from ground sources. The particles persist in the accumulation mode as expected for an aged aerosol. In the nocturnal boundary layer particle concentrations and size are more dynamic with higher concentrations than in the residual layer. A few hours after sunrise, the layered structure of the PBL intermixes. During daytime the PBL is well mixed and a negative concentration gradient with increasing height is observed. Several height profiles at different times of the day and at different locations in Europe were measured. The aerosol measurements will be discussed together with meteorological parameters and trace gas measurements. Acknowledgement: PEGASOS project funded by the European Commission and the Framework Program 7 (FP7-ENV-2010-265148).

  13. A multi-layer soil moisture data assimilation using support vector machines and ensemble particle filter

    NASA Astrophysics Data System (ADS)

    Yu, Zhongbo; Liu, Di; Lü, Haishen; Fu, Xiaolei; Xiang, Long; Zhu, Yonghua

    2012-12-01

    SummaryHybrid data assimilation (DA) is greatly used in recent hydrology and water resources research. In this study, one newly introduced technique, the ensemble particle filter (EnPF), formed by coupling ensemble Kalman filter (EnKF) with particle filter (PF), is applied for a multi-layer soil moisture prediction in the Meilin watershed based on the support vector machines (SVMs). The data used in this paper includes six-layer soil moisture: 0-5 cm, 30 cm, 50 cm, 100 cm, 200 cm and 300 cm and five meteorological parameters: soil temperature at 5 cm and 20 cm, air temperature, relative humidity and solar radiation in the study area. In order to investigate this EnPF approach, another two filters, EnKF and PF are applied as another two data assimilation methods to conduct a comparison. In addition, the SVM model simulated data without updating with data assimilation technique is discussed as well to evaluate the data assimilation technique. Two experimental cases are explored here, one with 200 initial training ensemble members in the SVM training phase while the other with 1000 initial training ensemble members. Three main findings are obtained in this study: (1) the SVMs machine is a statistically sound and robust model for soil moisture prediction in both the surface and root zone layers, and the larger the initial training data ensemble, the more effective the operator derived; (2) data assimilation technique does improve the performance of SVM modeling; (3) EnPF outweighs the performance of other two filters as well as the SVM model; Moreover, the ability of EnPF and PF is not positively related to the resampling ensemble size, when the resampling size exceeds a certain amount, the performance of EnPF and PF would be degraded. Because the EnPF still performs well than EnKF, it can be used as a powerful data assimilation tool in the soil moisture prediction.

  14. Gust structure in the neutral surface boundary layer

    SciTech Connect

    Doran, J.C.; Powell, D.C.

    1982-01-01

    Measured characteristics of gust amplitudes and times in the neutral surface boundary layer are presented. The probability of gust amplitudes exceeding a prescribed level is shown to decrease exponentially with amplitude, provided the amplitude is scaled with the root-mean-square turbulent speed. The 25 and 75 percentile conditional probabilities of gust duration obey power laws in the scaled amplitudes if the durations are normalized by N/sub 0/, the frequency of occurance of all gusts. These relationships are nearly independent of mean wind speed and measurement height. The effects of digital filtering of the data also are discussed.

  15. Atomic and molecular layer activation of dielectric surfaces

    NASA Astrophysics Data System (ADS)

    Senkevich, John Joseph

    Strong interaction between the material deposit and substrate is critical to stable deposits and interfaces. The work presented here focuses on the surface activation of dielectric surfaces and oxidized metal surfaces to promote the chemisorption of palladium (II) hexafluoroacetylacetonate (PdII (hfac)2). The goal is to develop reliable, robust metallization protocols, which enable strong interactions between the metal and substrate. SiO2, air exposed Ta, Trikon, and SiLK were activated with sulfur or phosphorus. Two types of activations were developed; one based on self-assembled chemistry, and the other a plasma-assisted process. Activation of the surface using self-assembly techniques was carried out using mercaptan-terminated silane and tetrasulfide silane. The resulting films were characterized by variable angle spectroscopic ellipsometry, contact angle goniometry, and X-ray photoelectron spectroscopy. Tetrasulfide silane sources films exhibit self-limiting behavior, even in the presence of water vapor; whereas mercaptan-terminated silane sourced films tend to be thicker. The surface activations using atomic layers of sulfur and phosphorus were carried out in a rf plasma chamber using hydrogen sulfide and phosphine sources, respectively. The activations were studied as functions of rf power, system pressure, and substrate material. Results show that higher rf powers and lower system pressures promote greater surface coverages by sulfur with a reduced oxidation state. The activated dielectrics show evidence of PdII(hfac)2 chemisorption, in contrast to non-activated surfaces. The binding energy shift of the Pd3d 5/2 XPS peak towards elemental Pd provides evidence for the dissociative chemisorption of PdII(hfac)2. The extent of dissociation depends on the substrate temperature and the activation method used. The conclusions of the work presented here have implications for metallization using highly polarizable transition metals. Specifically, it can be applied to the atomic layer and chemical vapor deposition of Pd. Another potential benefit is the activation of dielectric and oxidized metal surfaces for other deposition techniques; for example, to promote the chemisorption of copper ions from solution during electrochemical deposition of Cu.

  16. Elemental analyses of hypervelocity micro-particle impact sites on interplanetary dust experiment sensor surfaces

    NASA Technical Reports Server (NTRS)

    Simon, Charles G.; Hunter, J. L.; Griffis, D. P.; Misra, V.; Ricks, D. R.; Wortman, Jim J.

    1992-01-01

    The Interplanetary Dust Experiment (IDE) had over 450 electrically active ultra-high purity metal-oxide-silicon impact detectors located on the six primary sides of the Long Duration Exposure Facility (LDEF). Hypervelocity micro-particles that struck the active sensors with enough energy to breakdown the 0.4 to 1.0 micron thick SiO2 insulator layer separating the silicon base (the negative electrode), and the 1000 A thick surface layer of aluminum (the positive electrode) caused electrical discharges that were recorded for the first year of orbit. These discharge features, which include 50 micron diameter areas where the aluminum top layer has been vaporized, facilitate the location of the impacts. The high purity Al-SiO2-Si substrates allow detection of trace (ppm) amounts of hypervelocity impactor residues. After sputtering through a layer of surface contamination, secondary ion mass spectrometry (SIMS) is used to create two-dimensional elemental ion intensity maps of micro-particle impact sites on the IDE sensors. The element intensities in the central craters of the impacts are corrected for relative ion yields and instrumental conditions and then normalized to silicon. The results are used to classify the particles' origins as 'manmade', 'natural' or 'indeterminate'. The last classification results from the presence of too little impactor residue (a frequent occurrence on leading edge impacts), analytical interference from high background contamination, the lack of information on silicon residue, the limited usefulness of data on aluminum in the central craters, or a combination of these circumstances. Several analytical 'blank' discharges were induced on flight sensors by pressing down on the sensor surface with a pure silicon shard. Analyses of these blank discharges showed that the discharge energy blasts away the layer of surface contamination. Only Si and Al were detected inside the discharge zones, including the central craters, of these features. A total of 35 impacts on leading edge sensors and 22 impacts on trailing edge sensors were analyzed.

  17. Dust Devils on Mars: Effects of Surface Roughness on Particle Threshold

    NASA Technical Reports Server (NTRS)

    Neakrase, Lynn D.; Greeley, Ronald; Iversen, James D.; Balme, Matthew L.; Foley, Daniel J.; Eddlemon, Eric E.

    2005-01-01

    Dust devils have been proposed as effective mechanisms for lofting large quantities of dust into the martian atmosphere. Previous work showed that vortices lift dust more easily than simple boundary layer winds. The aim of this study is to determine experimentally the effects of non-erodable roughness elements on vortex particle threshold through laboratory simulations of natural surfaces. Additional information is included in the original extended abstract.

  18. MICROANALYSIS OF INDIVIDUAL LAYERED PARTICLES BY SECONDARY ION MASS SPECTROMETRY

    EPA Science Inventory

    Secondary ion mass spectrometry is evaluated for application to the determination of the composition and structure of individual particles. Analyses of many elemental constituents at the ppm level can be obtained in individual particles as small as micrometers in diameter. Molecu...

  19. Microstructures of tribologically modified surface layers in two-phase alloys

    NASA Astrophysics Data System (ADS)

    Figueroa, C. G.; Ortega, I.; Jacobo, V. H.; Ortiz, A.; Bravo, A. E.; Schouwenaars, R.

    2014-08-01

    When ductile alloys are subject to sliding wear, small increments of plastic strain accumulate into severe plastic deformation and mechanical alloying of the surface layer. The authors constructed a simple coaxial tribometer, which was used to study this phenomenon in wrought Al-Sn and cast Cu-Mg-Sn alloys. The first class of materials is ductile and consists of two immiscible phases. Tribological modification is observed in the form of a transition zone from virgin material to severely deformed grains. At the surface, mechanical mixing of both phases competes with diffusional unmixing. Vortex flow patterns are typically observed. The experimental Cu-Mg-Sn alloys are ductile for Mg-contents up to 2 wt% and consist of a- dendrites with a eutectic consisting of a brittle Cu2Mg-matrix with ?-particles. In these, the observations are similar to the Al-Sn Alloys. Alloys with 5 wt% Mg are brittle due to the contiguity of the eutectic compound. Nonetheless, under sliding contact, this compound behaves in a ductile manner, showing mechanical mixing of a and Cu2Mg in the top layers and a remarkable transition from a eutectic to cellular microstructure just below, due to severe shear deformation. AFM-observations allow identifying the mechanically homogenized surface layers as a nanocrystalline material with a cell structure associated to the sliding direction.

  20. Transport of spherical colloids in layered phases of binary mixtures with rod-like particles.

    PubMed

    Piedrahita, Mauricio; Cuetos, Alejandro; Martínez-Haya, Bruno

    2015-04-22

    The transport properties of colloids in anisotropic media constitute a general problem of fundamental interest in experimental sciences, with a broad range of technological applications. This work investigates the transport of soft spherical colloids in binary mixtures with rod-like particles by means of Monte Carlo and Brownian Dynamics simulations. Layered phases are considered, that range from smectic phases to lamellar phases, depending on the molar fraction of the spherical particles. The investigation serves to characterize the distinct features of transport within layers versus those of transport across neighboring layers, both of which are neatly differentiated. The insertion of particles into layers and the diffusion across them occur at a smaller rate than the intralayer diffusion modulated by the formation of transitory cages in its initial stages. Collective events, in which two or more colloids diffuse across layers in a concerted way, are described as a non-negligible process in these fluids. PMID:25797280

  1. Particle dispersion within zonal jets in two-layer beta-plane turbulence 

    E-print Network

    Roman, Jennifer Claire

    1996-01-01

    Passive tracer dispersion is studied in a two-layer, quasigeostrophic, betaplane model in which persistent, steady, zonal jets are observed. Particle trajectories and statistics are examined for barriers to or mechanisms for mixing. Simulations...

  2. The role of adsorbed water on the friction of a layer of submicron particles

    USGS Publications Warehouse

    Sammis, Charles G.; Lockner, David A.; Reches, Ze’ev

    2011-01-01

    Anomalously low values of friction observed in layers of submicron particles deformed in simple shear at high slip velocities are explained as the consequence of a one nanometer thick layer of water adsorbed on the particles. The observed transition from normal friction with an apparent coefficient near ? = 0.6 at low slip speeds to a coefficient near ? = 0.3 at higher slip speeds is attributed to competition between the time required to extrude the water layer from between neighboring particles in a force chain and the average lifetime of the chain. At low slip speeds the time required for extrusion is less than the average lifetime of a chain so the particles make contact and lock. As slip speed increases, the average lifetime of a chain decreases until it is less than the extrusion time and the particles in a force chain never come into direct contact. If the adsorbed water layer enables the otherwise rough particles to rotate, the coefficient of friction will drop to ? = 0.3, appropriate for rotating spheres. At the highest slip speeds particle temperatures rise above 100°C, the water layer vaporizes, the particles contact and lock, and the coefficient of friction rises to ? = 0.6. The observed onset of weakening at slip speeds near 0.001 m/s is consistent with the measured viscosity of a 1 nm thick layer of adsorbed water, with a minimum particle radius of approximately 20 nm, and with reasonable assumptions about the distribution of force chains guided by experimental observation. The reduction of friction and the range of velocities over which it occurs decrease with increasing normal stress, as predicted by the model. Moreover, the analysis predicts that this high-speed weakening mechanism should operate only for particles with radii smaller than approximately 1 ?m. For larger particles the slip speed required for weakening is so large that frictional heating will evaporate the adsorbed water and weakening will not occur.

  3. Velocity statistics in the atmospheric surface layer over a desert

    NASA Astrophysics Data System (ADS)

    Charuchittipan, Doojdao

    During "Dugway 2005," all atmospheric surface layer experiment performed over a Utah desert, sonic anemometers at heights up to 26 in above ground collected 20 Hz time series of the components (u, v, w) of wind velocity, and temperature (T). In this thesis Dugway statistics (1-hr intervals) are analyzed according to the tenets of Monin-Obukhov (MO) Similarity Theory, i.e. statistics have been normalized using as "natural scales" the friction velocity u*, the Obukhov length L, and a related temperature scale T* . Streamwise velocity spectra are computed, and the turbulent kinetic energy (TKE) dissipation rate (epsilon) and boundary layer depth (delta) deduced from them; epsilon is well approximated by the rate of production of TKE. Runs with extremely unstable stratification permit a cursory evaluation of McNaughton's alternative scaling theory, whose application requires as input the dissipation rate (epsilon0) of the "outer layer." For those cases Dugway statistics do order with z/zs, though not as tidily as they do under MO scaling.

  4. THEORETICAL MODEL OF SOILING OF SURFACES BY AIRBORNE PARTICLES

    EPA Science Inventory

    A model is developed which can be used to predict the change in reflectance from a surface as a function of time. Reflectance change is a measure of soiling caused by the deposition of particles on a surface. The major inputs to the model are the parameters to a bimodal distribut...

  5. Parametric Effects on Particle Deposition in Abrasive Waterjet Surface Treatments

    Microsoft Academic Search

    D. Arola; C. L. Hall

    2004-01-01

    The abrasive waterjet (AWJ) has primarily been used for net-shape sectioning of engineering materials. In this study an AWJ was adopted for the surface treatment of commercially pure titanium (cpTi) and the contribution of treatment parameters to material removal and the deposition of particles within the substrate were examined. The surface texture and material removal rate were analyzed using conventional

  6. MODELING PARTICLE DEPOSITION ON COMPRESSOR AND TURBINE BLADE SURFACES

    Microsoft Academic Search

    Hesham El-Batsh

    1. ABSTRACT Particle deposition on turbine blade surfaces is studied in this work. The turbine blade geometry is chosen from experimental results. The grid has been generated and adopted using software preBFC. The flow field is solved in FLUENT using k- ? Model. The velocity distribution deduced from the static pressure distribution on blade surface has been compared with that

  7. Real-time assessment of surface interactions with titanium passivation layer by surface plasmon resonance

    PubMed Central

    Hirata, Isao; Yoshida, Yasuhiro; Nagaoka, Noriyuki; Hiasa, Kyou; Abe, Yasuhiko; Maekawa, Kenji; Kuboki, Takuo; Akagawa, Yasumasa; Suzuki, Kazuomi; Van Meerbeek, Bart; Messersmith, Phillip B.; Okazaki, Masayuki

    2011-01-01

    The high corrosion resistance and strength-to-density ratio makes titanium widely used in major industry, but also in a gamut of medical applications. Here we report for the first time on our development of a titanium passivation layer sensor that makes use of surface plasmon resonance (SPR). The deposited titanium metal layer on the sensor was passivated in air, like titanium medical devices. Our ‘Ti-SPR sensor’ enables analysis of biomolecules interactions with the passivated surface of titanium in real time. As a proof of concept, corrosion of titanium passivation layer exposed to acid was monitored in real time. Also, the Ti-SPR sensor can accurately measure the time-dependence of protein adsorption onto titanium passivation layer with a sub-nanogram per square millimeter accuracy. Besides such SPR analyses, an SPR-imaging (SPRI) enables real-time assessment of chemical surface processes that occur simultaneously at ‘multiple independent spots’ on the Ti-SPR sensor, such as acid-corrosion or adhesion of cells. Our Ti-SPR sensor will therefore be very useful to study titanium-corrosion phenomena and biomolecular titanium-surface interactions with application in a broad range of industrial and biomedical fields. PMID:22154862

  8. A study of the erosion–corrosion behavior of nano-Cr 2O 3 particles reinforced Ni-based composite alloying layer in aqueous slurry environment

    Microsoft Academic Search

    Linlin Liu; Jiang Xu

    2011-01-01

    To investigate the role of nano-Cr2O3 particles on the erosion–corrosion behavior of composite alloying layer, a nano-Cr2O3 particles reinforced Ni-based composite alloying layer was fabricated onto AISI 316L stainless steel (SS) via a duplex surface treatment, consisting of Ni\\/nano-Cr2O3 predeposited by electric brush plating, and subsequent Ni–Cr–Mo–Cu multi-element surface alloying by a double glow process. The microstructure and composition of

  9. Utilization of surface-treated rubber particles from waste tires

    SciTech Connect

    Smith, F.G. [Argonne National Lab., IL (United States). Energy Systems Div.]|[Environmental Technologies Alternatives, Inc., Lima, OH (United States)

    1994-12-01

    During a 12-month program, the author successfully demonstrated commercial applications for surface-treated rubber particles in two major markets: footwear (shoe soles and components) and urethane-foam carpet underlay (padding). In these markets, he has clearly demonstrated the ease of using R-4080 and R-4030 surface-treated rubber particles in existing manufacturing plants and processes and have shown that the material meets or exceeds existing standards for performance, quality, and cost-effectiveness. To produce R-4080 and R-4030, vulcanized rubber, whole-tire material is finely ground to particles of nominal 80 and mesh size respectively. Surface treatment is achieved by reacting these rubber particles with chlorine gas. In this report, the author describes the actual test and evaluations of the participant companies, and identifies other potential end uses.

  10. DEM simulations and experiments for projectile impacting two-dimensional particle packings including dissimilar material layers

    Microsoft Academic Search

    Masahiro Nishida; Yusuke Tanaka

    2010-01-01

    The dynamic response of a two-dimensional ordered particle packing composed of nylon-66 spheres 6.35 mm in diameter impacted\\u000a by a spherical projectile was investigated both experimentally and numerically using the discrete element method (DEM). First,\\u000a the influence of the number of layers in the particle packing on wave propagation and post-impact movement were examined.\\u000a As the number of layers increased, the

  11. Polyvalent surface modification of hydrocarbon polymers via covalent layer-by-layer self-assembly 

    E-print Network

    Liao, Kang-Shyang

    2009-05-15

    -by-Layer Self-Assembly of PNIPAM-c-PNASI with Aminated Silica Nanoparticles (100 nm only) on PE Films ..................... 117 Preparation of PNIPAM Grafted (Gantrez/PEI) 4 -PE Surface by Atom Transfer Radical Polymerization.../MWNT-NH-PEI on PEI grafted oxidized PE films (4) and further acylation with a mixed anhydride prepared from ethyl chloroformate and octadecanoic acid (5)..... 74 6. Procedure for ionic LbL self-assembly of PAA/MWNT-NH-PEI on PEI grafted oxidized PE films (6...

  12. Imaging Layers Based on Surface-Initiated Polymers

    NASA Astrophysics Data System (ADS)

    Montague, Martha; Edwards, Erik; Nealey, Paul

    2002-03-01

    Photoresist structures at the 70 nm and 50 nm technology nodes are of molecular dimensions, and allowable tolerances and margins are of atomic dimensions. It is unclear whether current resist processing based on preferential solubility of protected or deprotected polymer molecules in aqueous base will afford the necessary process latitude at this scale. We are developing thin film imaging materials (100 to 200 nm thick) composed of polymer chains that are grafted (polymerized) directly on the surface of the substrate. These brushes have been grown from silicon wafers using "living" free radical initiators that are tethered to the surface of the wafer. We pattern this system by taking advantage of chemical amplification. An acid-labile linkage was incorporated into the tether of the polymer brush, and by using a photo acid generator we can create acid in exposed regions of our imaging layer. This strategy allows us to decouple the imaging process from the chemistry of the polymer. The resist then can be designed to optimize properties such as transparency and etch resistance. We will evaluate the imaging layers for process latitude and resolution.

  13. Contact damage in brittle coating layers: influence of surface curvature.

    PubMed

    Qasim, Tarek; Bush, Mark B; Hu, Xiaozhi; Lawn, Brian R

    2005-04-01

    Fracture from indentation by a hard sphere on bilayer systems composed of curved brittle coating layers on compliant polymeric substrates is investigated, in simulation of dental crown structures. Glass plates 1 mm thick are used as representative of enamel/crown layers, and epoxy filler substrates as representative of support dentin. Specimens with curved surfaces are prepared by pressing the glass plates onto steel sphere dies with radius of curvature down to 4 mm, to reflect common occlusal geometries. The influence of curvature on the conditions to initiate and propagate subsurface "radial" cracks, widely believed to be the principal failure mode in ceramic-based dental crowns, is studied. Finite element calculations are used to evaluate stress states in the specimens. It is shown that surface curvature can play an important role in the radial crack evolution, initially by inhibiting initiation but subsequently, in the case of convex curvature, by strongly enhancing propagation to failure. Implications concerning the design of ceramic-based dental crowns are considered. PMID:15625677

  14. Spectral characteristics of atmospheric surface layer turbulence in Qatar

    NASA Astrophysics Data System (ADS)

    Sadr, Reza; Singha, Arindam; Micro Scale Thermofluids Laboratory Team

    2012-11-01

    Turbulent characteristics of atmospheric boundary layer are of utmost importance in modeling the large-scale meteorological processes, diffusion of atmospheric contaminants, heat transfer and evaporation from the earth surface. Meteorological data are available for some areas of the globe but are sparse in tropical regions. There had been some recent studies in tropical weather in southwestern Asia but no study is carried out in Persian Gulf region. The present study reports the micrometeorological data collected from an atmospheric measurement station in the coastal region of Doha, Qatar, to characterize the nature of atmosphere surface layer (ASL) and ocean wave in this region. In the present work turbulence velocity spectra in this region is presented and compared with the available data from other locations. Also, empirical relationship for the normalized dissipation function in this region is suggested. Finally, variation of different length scales with the stability parameter z/ L is investigated and compare with the existing values in available literatures. This is the first ever study of ASL in this area, and is expected to be a foundation of further atmospheric research endeavors in Qatar.

  15. Thermal stability of nanocrystalline layers fabricated by surface nanocrystallization

    NASA Astrophysics Data System (ADS)

    Mai, Yong-jin; Jie, Xiao-hua; Liu, Li-li; Yu, Neng; Zheng, Xiang-xin

    2010-01-01

    A nanocrystalline layer with ultrafine grains (about 30-40 nm) on the surface of 7050 aluminum alloy was fabricated by a new technique called High Pressure Shot Peening (HPSP) which is the combination of common Shot Peening equipment with a pressurizing vessel. Relationship between hot flow and temperature was observed by Differential Scanning Calorimetry (DSC) and the activation energy, calculated by Kisssinger equation, of the as-treated sample increased 26.6 kJ/mol when it is compared with the as-reserved sample. The Bragg peaks of the as-prepared samples, respectively treated with various annealing treatments were characterized by XRD and the microhardness distribution along the depth from the treated surface were measured at the same time, which indicated that the broadening of Bragg peaks decreased with the increasing of anneal temperature; the grain size, calculated by Scherrer-Wilson equation, increased obviously during 180-220 °C, accordingly, the microhardness obviously decreased. According to the results of DSC, XRD and microhardness, it is reasonable to deduce that the temperature range of thermal stability for aluminum alloy nanocrystalline layer is lower than 200 °C.

  16. In situ ceramic layer growth on coated fuel particles dispersed in a zirconium metal matrix

    SciTech Connect

    Terrani, Kurt A [ORNL] [ORNL; Silva, G W Chinthaka M [ORNL; Kiggans, Jim [ORNL] [ORNL; Cai, Zhonghou [Argonne National Laboratory (ANL)] [Argonne National Laboratory (ANL); Shin, Dongwon [ORNL] [ORNL; Snead, Lance Lewis [ORNL] [ORNL

    2013-01-01

    The extent and nature of the chemical interaction between the outermost coating layer of coated fuel particles embedded in zirconium metal during fabrication of metal matrix microencapsulated fuels was examined. Various particles with outermost coating layers of pyrocarbon, SiC, and ZrC have been investigated in this study. ZrC-Zr interaction was least substantial while PyC-Zr reaction can be exploited to produce a ZrC layer at the interface in an in situ manner. The thickness of the ZrC layer in the latter case can be controlled by adjusting the time and temperature during processing. The kinetics of ZrC layer growth is significantly faster from what is predicted using literature carbon diffusivity data in ZrC. SiC-Zr interaction is more complex and results in formation of various chemical phases in a layered aggregate morphology at the interface.

  17. Nature of the Martian surface as inferred from the particle-size distribution of lunar-surface material.

    NASA Technical Reports Server (NTRS)

    Mason, C. C.

    1971-01-01

    Analysis of lunar particle size distribution data indicates that the surface material is composed of two populations. One population is caused by comminution from the impact of the larger-sized meteorites, while the other population is caused by the melting of fine material by the impact of smaller-sized meteorites. The results are referred to Mars, and it is shown that the Martian atmosphere would vaporize the smaller incoming meteorites and retard the incoming meteorites of intermediate and large size, causing comminution and stirring of the particulate layer. The combination of comminution and stirring would result in fine material being sorted out by the prevailing circulation of the Martian atmosphere and the material being transported to regions where it could be deposited. As a result, the Martian surface in regions of prevailing upward circulation is probably covered by either a rubble layer or by desert pavement; regions of prevailing downward circulation are probably covered by sand dunes.

  18. Engineering of an MBR supernatant fouling layer by fine particles addition: a possible way to control cake compressibility.

    PubMed

    Teychene, Benoît; Guigui, Christelle; Cabassud, Corinne

    2011-02-01

    For membrane bioreactors (MBR) applied to wastewater treatment membrane fouling is still the prevalent issue. The main limiting phenomena related to fouling is a sudden jump of the transmembrane pressure (TMP) often attributed to the collapse of the fouling layer. Among existing techniques to avoid or to delay this collapse, the addition of active particles membrane fouling reducers (polymer, resins, powdered activated carbon (PAC), zeolithe...) showed promising results. Thus the main objective of this work is to determine if fouling can be reduced by inclusion of inert particles (500 nm and inert compared to other fouling reducers) and which is the impact on filtration performances of the structuring of the fouling. Those particles were chosen for their different surface properties and their capability to form well structured layer. Results, obtained at constant pressure in dead end mode, show that the presence of particles changes foulant deposition and induces non-compressible fouling (in the range of 0.5-1 bar) and higher rejection values compared to filtration done on supernatant alone. Indeed dead end filtration tests show that whatever interactions between biofluid and particles, the addition of particles leads to better filtration performances (in terms of rejection, and fouling layer compressibility). Moreover results confirm the important role played by macromolecular compounds, during supernatant filtration, creating highly compressible and reversible fouling. In conclusion, this study done at lab-scale suggests the potential benefit to engineer fouling structure to control or to delay the collapse of the fouling layer. Finally this study offers the opportunities to enlarge the choice of membrane fouling reducers by taking into consideration their ability to form more consistent fouling (i.e. rigid, structured fouling). PMID:21232780

  19. Fabrication and application of responsive polymer surfaces on planar substrates and colloidal particles

    NASA Astrophysics Data System (ADS)

    Lupitskyy, Robert

    2009-11-01

    In the present dissertation, the problem of controlling interactions of material surfaces with the environment was addressed. Using chemical modification of surfaces with responsive polymers, it is possible to use external stimuli to regulate surface wettability, protein adsorption, stability, and interfacial properties of colloidal particles. The research work presented in this dissertation consists of four independent parts. In the first part (Chapter II), the responsive behavior of a novel heteroarm star-copolymer, poly(2-vinylpyridine)-star-poly(styrene) (PS7-P2VP7), was investigated. For grafted layers of PS7-P2VP7,surface composition, morphology, and wettability can be reversibly changed by treatment with solvents of different thermodynamic quality. Grafted layers of the star-copolymer exhibit a pronounced solvent-dependent phase segregation characteristic and behave similarly to mixed polymer brushes with incompatible components. In the second part (Chapter III), the regulation of fibrinogen adsorption by changing surface composition and microstructure of a mixed polymer brush was explored. The brush is a combination of a protein-repelling component, poly(ethylene glycol), and a protein-attracting component, poly(acrylic acid)-b-polystyrene. Treatment with different organic solvents changes the degree of adsorption of a test protein, fibrinogen, whereas treatment with calcium chloride solution results in virtually no protein adsorption at all. Studies of brush morphology and brush extension in aqueous medium revealed that treatment with different solvents results in different size and distribution of polystyrene domains, which in turn affects the adsorption of fibrinogen. In the third part (Chapter IV), a responsive colloidal system was developed by grafting poly(styrene-b-2-vinylpyridine-b-ethylene oxide) triblock copolymer onto the surface of 200 nm silica particles. This type of grafted polymer layer is both pH- and solvent-sensitive. These properties could be used for reversible formation of particle aggregates, for regulation of particles transport across the interface between immiscible liquids, and for stabilization of oil-water emulsions. In the last part (Chapter V), composite particles for optical indication of pH changes, based on the localized surface plasmon resonance of gold nanoparticles, were developed. Poly(2-vinylpyridine) grafted to the surface of silica particles was used as a host for 12 nm gold nanoparticles. Conformational transitions of the P2VP molecules, induced by pH changes, were transformed into a detectible optical signal by the gold nanoparticles.

  20. Influence of surface charge and particle size on the stabilization of colloidal particles by model polyelectrolytes

    Microsoft Academic Search

    Harold W. Walker

    1998-01-01

    In this study, a homologous series of single-stranded DNA homopolymers is used to investigate the effect of polymer molecular weight on the ability of polyelectrolytes to stabilize suspensions of polystyrene latex particles. The critical polymer length (CPL) required for stabilization depends strongly on the average diameter of the latex particles, and is not influenced by the surface charge of the

  1. Layer-by-Layer Surface Molecular Imprinting on Polyacrylonitrile Nanofiber Mats.

    PubMed

    Liu, Yuxuan; Cao, Bing; Jia, Peng; An, Junhu; Luo, Chao; Ma, Lijing; Chang, Jiao; Pan, Kai

    2015-06-25

    Surface molecular imprinting in layer-by-layer (SMI-LbL) film is known as a facile and effective strategy to build imprinting sites that are more accessible to template molecules compared with molecular imprinting in polymers. Herein, we accomplished the formation of SMI-LbL film on electrospun nanofibers for the first time. The SMI-LbL nanofibers were prepared by a template-induced LbL process on the polyacrylonitrile (PAN) nanofiber substrates, followed by postinfiltrating and photo-cross-linking of photosensitive agent 4,4'-diazostilbene-2,2'-disulfonic acid disodium salt (DAS). The obtained nanofiber mat maintained the nanofibrous structure and showed rapid absorption and extraction of template molecules of meso-tetra(4-carboxyphenyl)-porphine (Por). The binding capacity of Por reached 2.1 mg/g when 3.5 bilayers were deposited on the nanofibers. After six cycles of extraction and reabsorption, the binding capacity of Por remained at 83%. Moreover, the absorption results of the targeted templated molecule of Por and the control molecule of Fast Green, which had a very similar chemical structure and charge status to Por, indicated the specific absorption for template molecule of Por. Thus, a surface molecular imprinted nanofiber mat with high selectivity of the templated molecule has been demonstrated. PMID:26038802

  2. Entropic Trapping of Particles at Polymer Surfaces and Interfaces

    E-print Network

    Galen T. Pickett

    2015-05-22

    I consider the possibility that Gaussian random walk statistics are sufficient to trap nanoscopic additives at either a polymer interface or surface. When an additive particle goes to the free surface, two portions of the polymer surface energy behave quite differently. The purely enthalpic contribution increases the overall free energy when the additive protrudes above the level of the polymer matrix. The entropic part of the surface energy arising from constraints that segments near a surface can't cross it, is partly relaxed when the additive moves to the free surface. These two portions of the polymer surface energy determine the equilibrium wetting angle formed between the additive and the polymer matrix, the measurement of which in an experiment would allow an independent determination of each piece of the polymer surface energy.

  3. Numerical Simulation of Particle Dispersion in a Spatially Developing Mixing Layer

    NASA Astrophysics Data System (ADS)

    Hu, Zhiwei; Luo, Xiaoyu; Luo, Kai H.

    Although there have been several numerical studies on particle dispersion in mixing layers, most of them have been conducted for temporally evolving mixing layers. In this study, numerical simulations of a spatially developing mixing layer are performed to investigate particle dispersion under various conditions. The full compressible Navier--Stokes equations are solved with a high-order compact finite difference scheme, along with high-order time-integration. Accurate non-reflecting boundary conditions for the fluid flow are used, and several methods for introducing particles into the computational domain are tested. The particles are traced using a Lagrangian approach assuming one-way coupling between the continuous and the dispersed phases. The study focuses on the roles of the large-scale vortex structures in particle dispersion at low, medium and high Stokes numbers, which highlights the important effects of interacting vortex structures in nearby regions in the spatially developing mixing layer. The effects of particles with randomly distributed sizes (or Stokes numbers) are also investigated. Both instantaneous flow fields and statistical quantities are analyzed, which reveals essential features of particle dispersion in spatially developing free shear flows, which are different from those observed in temporally developing flows. The inclusion of the gravity not only modifies the overall dispersion patterns, but also enhances stream-crossing by particles.

  4. Characterization of cathode keeper wear by surface layer activation

    NASA Technical Reports Server (NTRS)

    Polk, James E.

    2003-01-01

    In this study, the erosion rates of the discharge cathode keeper in a 30 cm NSTAR configuration ion thruster were measured using a technique known as Surface Layer Activation (SLA). This diagnostic technique involves producing a radioactive tracer in a given surface by bombardment with high energy ions. The decrease in activity of the tracer material may be monitored as the surface is subjected to wear processes and correlated to a depth calibration curve, yielding the eroded depth. Analysis of the activities was achieved through a gamma spectroscopy system. The primary objectives of this investigation were to reproduce erosion data observed in previous wear studies in order to validate the technique, and to determine the effect of different engine operating parameters on erosion rate. The erosion profile at the TH 15 (23 kw) setting observed during the 8200 hour Life Demonstration Test (LDT) was reproduced. The maximum keeper erosion rate at this setting was determined to be 0.085 pm/hr. Testing at the TH 8 (1.4 kw) setting demonstrated lower erosion rates than TH 15, along with a different wear profile. Varying the keeper voltage was shown to have a significant effect on the erosion, with a positive bias with respect to cathode potential decreasing the erosion rate significantly. Accurate measurements were achieved after operating times of only 40 to 70 hours, a significant improvement over other erosion diagnostic methods.

  5. Exploring the bronzing effect at the surface of ink layers

    NASA Astrophysics Data System (ADS)

    Hébert, Mathieu; Mallet, Maxime; Deboos, Alexis; Chavel, Pierre; Kuang, Deng-Feng; Hugonin, Jean-Paul; Besbes, Mondher; Cazier, Anthony

    2015-03-01

    We investigate the optical phenomenon responsible for the colored shine that sometimes appears at the surface of ink layers in the specular direction, often called bronzing or gloss differential. It seems to come from the wavelength-dependent refractive index of the ink, which induces a wavelength-dependent reflectance of the ink-air interface. Our experiments on cyan and magenta inkjet inks confirm this theory. Complex refractive indices can be obtained from measurements of the spectral reflectance and transmittance of a transparency film coated with the ink. We propose a correction of the classical Clapper-Yule model in order to include the colored gloss in the prediction of the spectral reflectance of an inked paper. We also explored effects of scattering by the micrometric or nanometric roughness of the ink surface. The micrometric roughness, easy to model with a geometrical optics model, can predict the spreading of the colored gloss over a large cone. Electromagnetic models accounting for the effect of the nanometric roughness of the surface also predict the attenuation of short wavelengths observed under collimated illumination.

  6. Friction and wear behaviors of nanocrystalline surface layer of medium carbon steel

    Microsoft Academic Search

    Guobin Li; Jie Chen; Delin Guan

    2010-01-01

    A nanocrystalline (nc) surface layer, which is about 30?m thick, was fabricated on a medium carbon steel plate using high-energy shot peening (HESP). The tribological behavior of the nanocrystalline surface layer was investigated under the unlubricated slide using a ring-on-disc tester. The observation of the surface topography shows that the nanocrystalline surface layer may reduce the effect of fatigue wear

  7. Particle selection through topographic surface patterns in nematic colloids

    E-print Network

    Z. Eskandari; N. M. Silvestre; M. M. Telo da Gama; M. R. Ejtehadi

    2014-06-03

    We propose the use of topographic modulation of surfaces to select and localize particles in nematic colloids. By considering convex and concave deformations of one of the confining surfaces we show that the colloid-flat surface repulsion may be enhanced or switched into an attraction. In particular, we find that when the colloidal particles have the same anchoring conditions as the patterned surfaces, they are strongly attracted to concave dimples, while if they exhibit different anchoring conditions they are pinned at the top of convex protrusions. Although dominated by elastic interactions the first mechanism is reminiscent of the depletion induced attraction or of the key-lock mechanism, while the second is specific to liquid crystal colloids. These long-ranged, highly tunable, surface-colloid interactions contribute for the development of template-assisted assembly of large colloidal crystals, with well defined symmetries, required for applications.

  8. Method and apparatus for measuring surface density of explosive and inert dust in stratified layers

    DOEpatents

    Sapko, Michael J. (Finleyville, PA); Perlee, Henry E. (Bethel Park, PA)

    1988-01-01

    A method for determining the surface density of coal dust on top of rock dust or rock dust on top of coal dust is disclosed which comprises directing a light source at either a coal or rock dust layer overlaying a substratum of the other, detecting the amount of light reflected from the deposit, generating a signal from the reflected light which is converted into a normalized output (V), and calculating the surface density from the normalized output. The surface density S.sub.c of coal dust on top of rock dust is calculated according to the equation: S.sub.c =1/-a.sub.c ln(V) wherein a.sub.c is a constant for the coal dust particles, and the surface density S.sub.r of rock dust on top of coal dust is determined by the equation: ##EQU1## wherein a.sub.r is a constant based on the properties of the rock dust particles. An apparatus is also disclosed for carrying out the method of the present invention.

  9. Detection of charged particles in thick hydrogenated amorphous silicon layers

    SciTech Connect

    Fujieda, I.; Cho, G.; Kaplan, S.N.; Perez-Mendez, V.; Qureshi, S.; Ward, W.; Street, R.A.

    1988-03-01

    We show our results in detecting particles of various linear energy transfer, including minimum ionizing electrons from a Sr-90 source with 5 to 12 micron thick n-i-p and p-i-n diodes. We measured W ( average energy to produce one electron-hole pair) using 17keV filtered xray pulses with a result W = 6.0 /+-/ 0.2eV. This is consistent with the expected value for a semiconductor with band gap of 1.7 to 1.9eV. With heavily ionizing particles such as 6 MeV alphas and 1 to 2 MeV protons, there was some loss of signal due to recombination in the particle track. The minimum ionizing electrons showed no sign of recombination. Applications to pixel and strip detectors for physics experiments and medical imaging will be discussed. 7 refs., 8 figs.

  10. Bi-layered polymer–magnetite core\\/shell particles: synthesis and characterization

    Microsoft Academic Search

    M. S. A. Darwish; U. Peuker; U. Kunz; T. Turek

    2011-01-01

    Polymer magnetic core particles receive growing attention due to these materials owing magnetic properties which are widely\\u000a used in different applications. The prepared composite particles are characterized with different properties namely: a magnetic\\u000a core, a hydrophobic first shell, and finally an external second hydrophilic shell. The present study describes a method for\\u000a the preparation of bi-layered polymer magnetic core particles

  11. [Chemical modification on the surface of nano-particles of ZnO and its characterization].

    PubMed

    Yu, Hai-yin; Du, Jun; Gu, Jia-shan; Guan, Ming-yun; Wu, Zheng-cui; Ling, Qing; Sun, Yi-min

    2004-02-01

    After nano-particles (ZnO) had been encapsulated by a kind of water-soluble cellulose Hydoxyl-Propyl-Methyl Cellulose (HPMC), then methyl methacrylate was grafted onto the surface of them. Thus the surface of nano-ZnO had been successfully modified. FTIR, DTA and TEM were utilized to confirm the results. FTIR shows that HPMC was adsorbed onto the surface of ZnO, and PMMA was also grafted onto its surface, DTA says that the heat stability of HPMC, HPMC-g-PMMA and ZnO/HPMC-g-PMMA increased greatly, TEM photo demonstrates that polymer adhered onto the surface of nano-ZnO which was encapsulated by a layer of film-like polymer. PMID:15769010

  12. Numerical simulation of particle-wave interaction in boundary layers

    NASA Technical Reports Server (NTRS)

    Biringen, S.; Danabasoglu, G.

    1990-01-01

    The effects of wall injection and particle motion on the spatial stability of two-dimensional plane channel flow are investigated. For this purpose, an accurate Navier-Stokes solver to simulate the space-time evolution of disturbances in three-dimensional flows has been developed. The code is operational on the NASA Langley CRAY2 and can be ported to any other supercomputer. The code has been tested extensively in tracking the spatial evolution of two-dimensional disturbances in plane channel flow and provided excellent agreement with the linear theory including at the inflow/outflow boundaries. Preliminary calculations have been performed to investigate the effects of stationary and moving sources of vortical disturbances simulating a particle traveling in the flow field. Results suggest that even at very low amplitudes, vortical disturbances act as amplifiers on the Tollmien-Schlichting waves promoting rapid instability. It is also found that slow moving particles are more dangerous than both stationary and fast moving particles for the same disturbance levels.

  13. Detection of charged particles in amorphous silicon layers

    SciTech Connect

    Perez-Mendez, V.; Morel, J.; Kaplan, S.N.; Street, R.A.

    1986-02-01

    The successful development of radiation detectors made from amorphous silicon could offer the possibility for relatively easy construction of large area position-sensitive detectors. We have conducted a series of measurements with prototype detectors, on signals derived from alpha particles. The measurement results are compared with simple model calculations, and projections are made of potential applications in high-energy and nuclear physics.

  14. GYROSCOPIC PUMPING IN THE SOLAR NEAR-SURFACE SHEAR LAYER

    SciTech Connect

    Miesch, Mark S. [High Altitude Observatory, National Center for Atmospheric Research, Boulder, CO 80307-3000 (United States); Hindman, Bradley W., E-mail: miesch@ucar.edu [JILA and Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80309-0440 (United States)

    2011-12-10

    We use global and local helioseismic inversions to explore the prevailing dynamical balances in the solar near-surface shear layer (NSSL). The differential rotation and meridional circulation are intimately linked, with a common origin in the turbulent stresses of the upper solar convection zone. The existence and structure of the NSSL cannot be attributed solely to the conservation of angular momentum by solar surface convection, as is often supposed. Rather, the turbulent angular momentum transport accounts for the poleward meridional flow while the often overlooked meridional force balance is required to maintain the mid-latitude rotational shear. We suggest that the base of the NSSL is marked by a transition from baroclinic to turbulent stresses in the meridional plane which suppress Coriolis-induced circulations that would otherwise establish a cylindrical rotation profile. The turbulent angular momentum transport must be nondiffusive and directed radially inward. Inferred mean flows are consistent with the idea that turbulent convection tends to mix angular momentum but only if the mixing efficiency is inhomogeneous and/or anisotropic. The latitudinal and longitudinal components of the estimated turbulent transport are comparable in amplitude and about an order of magnitude larger than the vertical component. We estimate that it requires 2%-4% of the solar luminosity to maintain the solar NSSL against the inertia of the mean flow. Most of this energy is associated with the turbulent transport of angular momentum out of the layer, with a spin-down timescale of {approx}600 days. We also address implications of these results for numerical modeling of the NSSL.

  15. Electrostatic double layers as auroral particle accelerators - a problem

    NASA Astrophysics Data System (ADS)

    Bryant, D. A.; Courtier, G. M.

    2015-04-01

    A search of the Annales Geophysicae database shows that double layers and other quasi-static electric potential structures have been invoked hundreds of times since the year 2000 as being the agents of auroral electron acceleration. This is despite the fact that energy transfer by conservative fields has been known for some 200 years to be impossible. Attention is drawn to a long-standing interpretation of the acceleration process in terms of the dynamic fields of electrostatic waves.

  16. Functionalization of direct-emulsion disperse-phase surface by zinc oxide nanoparticles using layer-by-layer electrostatic assembly

    Microsoft Academic Search

    O. A. Inozemtseva; T. A. Kolesnikova; D. A. Gorin; N. V. Shvyndina; V. Ya. Shklover

    2011-01-01

    Polyelectrolyte and nanocomposite (zinc oxide nanoparticles\\/polymer) coatings on the surface of a direct-emulsion disperse\\u000a phase containing fluorescent dye were obtained using layer-by-layer electrostatic assembly. The volume fraction of inorganic\\u000a nanoparticles was varied by changing the number of polymer layers in the coating. The loaded microcontainers were characterized\\u000a by fluorescence confocal and scanning electron microscopy (SEM). The parameters influencing the quality

  17. Remote sensing of Arctic boundary layer clouds above snow surfaces

    NASA Astrophysics Data System (ADS)

    Ehrlich, André; Bierwirth, Eike; Wendisch, Manfred

    2015-04-01

    In the Arctic remote sensing of clouds using reflected solar radiation is mostly related to high uncertainties as the contrast between the bright sea ice and snow surface and the clouds is low. Additionally, uncertainties result from variation of the snow grain size which changes the absorption of solar radiation similarly to the size of cloud particles. This is a major issue for understanding the response of Arctic clouds to climate warming as the quantification of cloud properties in this remote region mostly relies on satellite observations. We used spectral radiation measurements of the Spectral Modular Airborne Radiation measurement sysTem (SMART-Albedometer) to improve common used cloud remote sensing algorithms in case of snow surfaces. The measurements were collected during the airborne research campaign Vertical distribution of ice in Arctic mixed-phase clouds (VERDI, April/May 2012) above the Canadian Beaufort where both sea ice covered and ice free ocean areas were present during the observation period. Based on the spectral absorption characteristics of snow and clouds (assuming to be dominated by the liquid fraction) a combination of wavelengths was found which allows to separate the impact of clouds and snow surface on the reflected radiation measured above the clouds. While snow grain size dominates the absorption at a wavelength of 1.0 ?m, information on cloud optical thickness and cloud particle effective radius can be extracted at wavelengths of 1.7 ?m and 2.1 ?m, respectively. Based on radiative transfer simulations lookup tables for the retrieval algorithm were calculated and used to estimate the theoretical uncertainties of the retrieval. It was found that using ratios instead of absolute radiances reduces the uncertainties significantly. The new algorithm was applied to a specific case observed during the VERDI campaign where a stratocumulus clouds was located above an ice edge. It could be shown that the method works also over water surfaces and provides similar cloud optical properties above ice covered and ice free surfaces. In addition the snow grain size could be derived also in cloud covered areas.

  18. Copolyimide Surface Modifying Agents for Particle Adhesion Mitigation

    NASA Technical Reports Server (NTRS)

    Wohl, Christopher J.; Connell, John W.

    2011-01-01

    Marine biofouling, insect adhesion on aircraft surfaces, microbial contamination of sterile environments, and particle contamination all present unique challenges for which researchers have adopted an array of mitigation strategies. Particulate contamination is of interest to NASA regarding exploration of the Moon, Mars, asteroids, etc.1 Lunar dust compromised seals, clogged filters, abraded visors and space suit surfaces, and was a significant health concern during the Apollo missions.2 Consequently, NASA has instituted a multi-faceted approach to address dust including use of sacrificial surfaces, active mitigation requiring the use of an external energy source, and passive mitigation utilizing materials with an intrinsic resistance to surface contamination. One passive mitigation strategy is modification of a material s surface energy either chemically or topographically. The focus of this paper is the synthesis and evaluation of novel copolyimide materials with surface modifying agents (SMA, oxetanes) enabling controlled variation of surface chemical composition.

  19. Comparing surface particle coverage predictions with image analysis measurements

    NASA Astrophysics Data System (ADS)

    Chang, Chien W.

    2006-08-01

    This paper describes a numerical model developed recently using MATLAB ® for performing surface particle coverage calculations. The model uses a multi-bin particle size distribution model with incorporation of Barengoltz's areal density integration method and Raab's particle shape factor, a similar approach employed previously by Ma, Fong and Lee at Lockheed Martin Space Systems Company (Sunnyvale). The developed model is a versatile and quick turnaround tool and can easily account for variable particle size bins, variable shape factors or aspect ratios for various size bins, and variable slopes (w.r.t. the IEST-STD-CC1246 slope) for different size bins. Model predictions compare well with image analysis measurements of particle fallout data from various spacecraft cleanrooms and test environments. Moreover, this study recommends using a standard equation to correlate particle area coverage with IEST-STD-CC1246 levels (particles modeled as a cylinder with hemispherical ends) and applying a wide range of conversion factors for accurately calculating particle area coverage for variable slopes for different particle size bins.

  20. Particle production from marginally trapped surfaces of general spacetimes

    NASA Astrophysics Data System (ADS)

    Senovilla, José M. M.; Torres, Ramón

    2015-04-01

    We provide a general formalism that allows us to analyze the phenomenon of tunneling in arbitrary spacetimes. We show that a flux of particles produced by tunneling through general marginally trapped surfaces (MTSs) may be perceived by some privileged observers. We discuss how this particle perception can be related to Hawking/Unruh radiation in specific cases. Our approach naturally leads to an expression for the effective surface gravity of MTSs. The procedure is applicable to general astrophysical and cosmological dynamical situations. Some practical examples for known and new cases are provided.

  1. Functionalization of Ag nanoparticles using local hydrophilic pool segment designed on their particle surface

    NASA Astrophysics Data System (ADS)

    Iijima, Motoyuki; Kurumiya, Aki; Esashi, Junki; Miyazaki, Hayato; Kamiya, Hidehiro

    2014-10-01

    The preparation of SiO2-coated Ag nanoparticles dispersible in various organic solvents has been achieved using a solgel reaction of tetraethylorthosilicate (TEOS), in the localized hydrophilic pool segments designed on Ag nanoparticle surfaces. First, oleylamine-capped core Ag nanoparticles were synthesized, followed by ligand exchange with polyethyleneimine (PEI) and further adsorption of an anionic surfactant comprising hydrophilic polyethylene glycol (PEG) chains and hydrophobic alkyl chains, which has previously been reported to improve the stability of nanoparticles in various solvents. Then, a reaction of TEOS with the localized hydrophilic PEI layer on the Ag nanoparticles' surface was conducted by stirring a toluene/TEOS solution of surface-modified Ag nanoparticles at various temperatures. It was found that a SiO2 layer was successfully formed on Ag nanoparticles when the reaction temperature was increased to 60 °C. It was also found, however, that at this elevated temperature, the primary particle size of Ag nanoparticles increased to several tens of nm, attributable to the dissolution and re-reduction of Ag+. Because the surface modifier, PEI and anionic surfactant all remained on the nanoparticle surface during the SiO2 coating process, the prepared SiO2-coated Ag nanoparticles were found to be dispersible in various organic solvents near to their primary particle size.

  2. On the Interaction between Marine Boundary Layer Cellular Cloudiness and Surface Heat Fluxes

    SciTech Connect

    Kazil, J.; Feingold, G.; Wang, Hailong; Yamaguchi, T.

    2014-01-02

    The interaction between marine boundary layer cellular cloudiness and surface uxes of sensible and latent heat is investigated. The investigation focuses on the non-precipitating closed-cell state and the precipitating open-cell state at low geostrophic wind speed. The Advanced Research WRF model is used to conduct cloud-system-resolving simulations with interactive surface fluxes of sensible heat, latent heat, and of sea salt aerosol, and with a detailed representation of the interaction between aerosol particles and clouds. The mechanisms responsible for the temporal evolution and spatial distribution of the surface heat fluxes in the closed- and open-cell state are investigated and explained. It is found that the horizontal spatial structure of the closed-cell state determines, by entrainment of dry free tropospheric air, the spatial distribution of surface air temperature and water vapor, and, to a lesser degree, of the surface sensible and latent heat flux. The synchronized dynamics of the the open-cell state drives oscillations in surface air temperature, water vapor, and in the surface fluxes of sensible and latent heat, and of sea salt aerosol. Open-cell cloud formation, cloud optical depth and liquid water path, and cloud and rain water path are identified as good predictors of the spatial distribution of surface air temperature and sensible heat flux, but not of surface water vapor and latent heat flux. It is shown that by enhancing the surface sensible heat flux, the open-cell state creates conditions by which it is maintained. While the open-cell state under consideration is not depleted in aerosol, and is insensitive to variations in sea-salt fluxes, it also enhances the sea-salt flux relative to the closed-cell state. In aerosol-depleted conditions, this enhancement may replenish the aerosol needed for cloud formation, and hence contribute to the perpetuation of the open-cell state as well. Spatial homogenization of the surface fluxes is found to have only a small effect on cloud properties in the investigated cases. This indicates that sub-grid scale spatial variability in the surface flux of sensible and latent heat and of sea salt aerosol may not be required in large scale and global models to describe marine boundary layer cellular cloudiness.

  3. Detection of charged particles in amorphous silicon layers

    SciTech Connect

    Kaplan, S.N.; Morel, J.R.; Mulera, T.A.; Perez-Mendez, V.; Schnurmacher, G.; Street, R.A.

    1985-10-01

    The successful development of radiation detectors made from amorphous silicon could offer the possibility for relatively easy construction of large area position-sensitive detectors. We have conducted a series of measurements with prototype detectors, on signals derived from alpha particles. The measurement results are compared with simple model calculations, and projections are made of potential applications in high-energy and nuclear physics. 4 refs., 7 figs.

  4. Charged particle detectors made from thin layers of amorphous silicon

    SciTech Connect

    Morel, J.R.

    1986-05-01

    A series of experiments was conducted to determine the feasibility of using hydrogenated amorphous silicon (..cap alpha..-Si:H) as solid state thin film charged particle detectors. /sup 241/Am alphas were successfully detected with ..cap alpha..-Si:H devices. The measurements and results of these experiments are presented. The problems encountered and changes in the fabrication of the detectors that may improve the performance are discussed.

  5. Diffusion layers produced on carbon steel surface by means of vacuum chromizing process

    Microsoft Academic Search

    Ewa Kasprzycka; Jan Senatorski; Aleksander Nakonieczny; Tomasz Babul

    2003-01-01

    This work investigated diffusion layers produced on carbon (C) steel surfaces in the vacuum chromizing process. Studies of\\u000a layer, thickness, morphology, and chromium (Cr), C, and iron (Fe) concentration depth profiles in the diffusion zone of chromized\\u000a layers were carried out. The effect of process parameters such as time and temperature on the kinetics of layer growth on\\u000a steel surface

  6. Investigation of morphology and fractal behaviour on compound semiconductor surface after electrochemical layer removal

    Microsoft Academic Search

    Ákos Nemcsics; Imre Mojzes; László Dobos

    1999-01-01

    The electrochemical method is a very versatile tool for characterization and processing of compound semiconductors. In this paper we investigate the surface morphology and pattern formation of GaAs and InP surfaces after electrochemical layer removal. Different aqueous HCl based electrolites were used for the layer removal. The investigation of the surface pattern formation was carried out using the box counting

  7. Thermal-induced inverse ?\\/?? phase transformation in surface nanocrystallization layer of 304 stainless steel

    Microsoft Academic Search

    A. Y. Chen; J. B. Zhang; H. W. Song; J. Lu

    2007-01-01

    Thermal stability of the surface nanocrystallization layer of 304 stainless steel prepared by surface mechanical attrition was studied. The XRD results revealed that the surface nanocrystalline layer was composed of ? austenite and ?? martensite phase, and the nanocrystalline kept good size stability under the thermal treatment as high as 773 K. However, according to the Mössbauer spectroscopy analysis, the ??

  8. The Effect of Contact Angle on the Depletion Layer when Water Meets a Hydrophobic Surface

    NASA Astrophysics Data System (ADS)

    Poynor, Adele

    2013-03-01

    By definition hydrophobic substances hate water. Water placed on a hydrophobic surface will form a drop in order to minimize its contact area. What happens when water is forced into contact with a hydrophobic surface? One theory is that an ultra-thin low-density depletion layer forms near the surface. We investigate the effect of contact angle on depletion layer formation using the surface sensitive technique of Surface Plasmon Resonance.

  9. New Material Development for Surface Layer and Surface Technology in Tribology Science to Improve Energy Efficiency

    NASA Astrophysics Data System (ADS)

    Ismail, R.; Tauviqirrahman, M.; Jamari, Jamari; Schipper, D. J.

    2009-09-01

    This paper reviews the development of new material and surface technology in tribology and its contribution to energy efficiency. Two examples of the economic benefits, resulted from the optimum tribology in the transportation sector and the manufacturing industry are discussed. The new materials are proposed to modify the surface property by laminating the bulk material with thin layer/coating. Under a suitable condition, the thin layer on a surface can provide a combination of good wear, a low friction and corrosion resistance for the mechanical components. The innovation in layer technology results molybdenum disulfide (MoS2), diamond like carbon (DLC), cubic boron nitride (CBN) and diamond which perform satisfactory outcome. The application of the metallic coatings to carbon fibre reinforced polymer matrix composites (CFRP) has the capacity to provide considerable weight and power savings for many engineering components. The green material for lubricant and additives such as the use of sunflower oil which possesses good oxidation resistance and the use of mallee leaves as bio-degradable solvent are used to answer the demand of the environmentally friendly material with good performance. The tribology research implementation for energy efficiency also touches the simple things around us such as: erasing the laser-print in a paper with different abrasion techniques. For the technology in the engineering surface, the consideration for generating the suitable surface of the components in running-in period has been discussed in order to prolong the components life and reduce the machine downtime. The conclusion, tribology can result in reducing manufacturing time, reducing the maintenance requirements, prolonging the service interval, improving durability, reliability and mechanical components life, and reducing harmful exhaust emission and waste. All of these advantages will increase the energy efficiency and the economic benefits.

  10. Layer-like Structure of Radio-Frequency Discharge with Dust Particles

    SciTech Connect

    Kravchenko, O. Y.; Vakulenko, A. V.; Lisitchenko, T. Y.; Levada, G. I. [National Taras Shevchenko University of Kyiv, Volodymirs'ka str. 64, 01033 Kyiv (Ukraine)

    2008-09-07

    In this paper we are carried out the computer simulation of the dust particles dynamics in the radio frequency discharges at the microgravity conditions using PIC/MCC method for electrons and ions and hydrodynamics model for dust particles. The moving of dust particles is governed by the electrostatic force, ion and neutral drag forces, which are averaged over period of RF discharge. The obtained results show that dust particles form layers with sharp boundaries in the discharge chamber that is response on the instability of the radio-frequency discharge.

  11. [Particle dispersion by ordered motion in mixing layers]. [Annual report

    SciTech Connect

    Troutt, T.R.

    1989-12-31

    Multiphase mixing in turbulent flows is a key element in many practical energy conversion, chemical mixing and pollutant dispersal problems. Numerous important technological and environmental processes could be better addressed with improvements in understanding in this area. Progress in developing understanding of this field, however, has traditionally been difficult because of the complexities involved with the turbulent flows employed to provide the mixing mechanisms. To address this problem from a new perspective several years ago this research group initiated an ongoing investigation concerning the potential connections between organized turbulent vortex structures and the particle dispersion process. This report details activities during this reporting period.

  12. Effective modification of particle surface properties using ultrasonic water mist.

    PubMed

    Genina, Natalja; Räikkönen, Heikki; Heinämäki, Jyrki; Antikainen, Osmo; Siiriä, Simo; Veski, Peep; Yliruusi, Jouko

    2009-01-01

    The goal of the present study was to design a new technique to modify particle surface properties and, through that, to improve flowability of poorly flowing drug thiamine hydrochloride and pharmaceutical sugar lactose monohydrate of two different grades. The powdered particles were supplied by a vibratory feeder and exposed to an instantaneous effect of water mist generated from an ultrasound nebulizer. The processed and original powders were evaluated with respect to morphology (scanning electron microscopy, atomic force microscopy, and spatial filtering technique), flow, and solid state properties. It was found that rapid exposition of pharmaceutical materials by water mist resulted in the improvement of powder technical properties. The evident changes in flowability of coarser lactose were obviously due to smoothing of particle surface and decreasing in the level of fines with very slight increment in particle size. The changes in thiamine powder flow were mainly due to narrowing in particle size distribution where the tendency for better flow of finer lactose was related to surface and size modifications. The aqueous mist application did not cause any alteration of the crystal structures of the studied materials. The proposed water mist treatment technique appears to be a robust, rapid, and promising tool for the improvement of the technological properties of pharmaceutical powders. PMID:19288203

  13. Surface-modified hemispherical polystyrene/polybutyl methacrylate composite particles.

    PubMed

    Akiva, Udi; Margel, Shlomo

    2005-08-01

    Micrometer-sized polystyrene/poly(n-butyl methacrylate) composite particles of hemisphere morphology and narrow size distribution were prepared by a process of single-step swelling of uniform polystyrene template microspheres with emulsion droplets of the monomer n-butyl methacrylate containing the initiator benzoyl peroxide in the presence, or absence, of the co-swelling agent toluene. Butyl methacrylate was then polymerized at 73 degrees C within the template microspheres. Surface and bulk characterization of the particles were performed by methods such as FTIR, elemental analysis, XPS, advancing contact angle, light microscope, SEM, and cross-sectional TEM. Selective surface functionalization of the poly(n-butyl methacrylate) phase of the composite particles was performed by carrying out a similar swelling and polymerization process in the presence of a water-soluble vinylic monomer such as acrylamide. PMID:15927562

  14. Enhanced erythrocyte suspension layer stability achieved by surface tension lowering additives

    NASA Technical Reports Server (NTRS)

    Omenyi, S. N.; Snyder, R. S.; Absolom, D. R.; Van Oss, C. J.; Neumann, A. W.

    1982-01-01

    In connection with a fractionation procedure involving the separation of particles, a dilute suspension of these particles in a liquid is carefully layered on a dense liquid. Under ideal conditions, the suspension forms a zone of finite thickness with a 'sharp' interface between the suspension layer and the supporting liquid. Under an applied field, e.g., gravitational or electrical, the particles in the suspension layer migrate to form different layers according to their size and/or density or according to their electrophoretic mobilities. However, in many cases the ideal conditions necessary for the fractionation process are not obtained. Many studies have been conducted to explore the reasons for suspension layer 'instability'. The present investigation represents an extension of a study conducted by Omenyi et al. (1981). An electrostatic repulsion-van der Waals mechanism was used to study the stability of fixed erythrocyte suspensions layered on a D2O cushion.

  15. The surface and through crack problems in layered orthotropic plates

    NASA Technical Reports Server (NTRS)

    Erdogan, Fazil; Wu, Binghua

    1991-01-01

    An analytical method is developed for a relatively accurate calculation of Stress Intensity Factors in a laminated orthotropic plate containing a through or part-through crack. The laminated plate is assumed to be under bending or membrane loading and the mode 1 problem is considered. First three transverse shear deformation plate theories (Mindlin's displacement based first-order theory, Reissner's stress-based first-order theory, and a simple-higher order theory due to Reddy) are reviewed and examined for homogeneous, laminated and heterogeneous orthotropic plates. Based on a general linear laminated plate theory, a method by which the stress intensity factors can be obtained in orthotropic laminated and heterogeneous plates with a through crack is developed. Examples are given for both symmetrically and unsymmetrically laminated plates and the effects of various material properties on the stress intensity factors are studied. In order to implement the line-spring model which is used later to study the surface crack problem, the corresponding plane elasticity problem of a two-bonded orthotropic plated containing a crack perpendicular to the interface is also considered. Three different crack profiles: an internal crack, an edge crack, and a crack terminating at the interface are considered. The effect of the different material combinations, geometries, and material orthotropy on the stress intensity factors and on the power of stress singularity for a crack terminating at the interface is fully examined. The Line Spring model of Rice and Levy is used for the part-through crack problem. The surface crack is assumed to lie in one of the two-layered laminated orthotropic plates due to the limitation of the available plane strain results. All problems considered are of the mixed boundary value type and are reduced to Cauchy type of singular integral equations which are then solved numerically.

  16. Wettability of terminally anchored polymer brush layers on a polyamide surface.

    PubMed

    Varin, Kari J Moses; Cohen, Yoram

    2014-12-15

    Surface wettability of terminally anchored hydrophilic polymer brush layers on polyamide-silicon (PA-Si) surfaces was evaluated with respect to surface topography at the nanoscale. Hydrophilic polyvinylpyrrolidone (PVP) and polyacrylamide (PAAm) brush layers were synthesized via graft polymerization onto a PA-Si surface previously activated by surface treatment with atmospheric pressure plasma. Hydrophilicity (or wettability) of the PA substrate, as quantified by the free energy of hydration, was increased upon surface coverage with the PVP and PAAm brush layers by 13-24% (-101.4 to -111.3 mJ/m(2)) and 19-37% (-106.1 to -122.4 mJ/m(2)), respectively. Surface hydrophilicity increased with both increasing surface roughness (0.55-2.89 nm and 1.54-5.84 nm for PVP and PAAm, respectively) and polymer volume (1.3×10(6)-7.3×10(6) nm(3)/?m(2) and 3.3×10(6)-2.8×10(7) nm(3)/?m(2) for PVP and PAAm surfaces, respectively). The present study suggests that a specific level of surface wettability can be attained by tailor-designing the polymer brush layer's physicochemical characteristics (e.g., surface roughness, wettability, and polymer water affinity) by adjusting surface topography and surface chemistry, which are controlled by surface activation and polymerization conditions. The above indicates that there is merit in structuring various surfaces with hydrophilic brush layers to increase surface wettability in membrane filtration, biomedical devices, and lubrication applications. PMID:25305445

  17. Layered reactive particles with controlled geometries, energies, and reactivities, and methods for making the same

    DOEpatents

    Fritz, Gregory M; Knepper, Robert Allen; Weihs, Timothy P; Gash, Alexander E; Sze, John S

    2013-04-30

    An energetic composite having a plurality of reactive particles each having a reactive multilayer construction formed by successively depositing reactive layers on a rod-shaped substrate having a longitudinal axis, dividing the reactive-layer-deposited rod-shaped substrate into a plurality of substantially uniform longitudinal segments, and removing the rod-shaped substrate from the longitudinal segments, so that the reactive particles have a controlled, substantially uniform, cylindrically curved or otherwise rod-contoured geometry which facilitates handling and improves its packing fraction, while the reactant multilayer construction controls the stability, reactivity and energy density of the energetic composite.

  18. Hierarchically structured superhydrophobic coatings fabricated by successive Langmuir Blodgett deposition of micro-\\/nano-sized particles and surface silanization

    Microsoft Academic Search

    Ping-Szu Tsai; Yu-Min Yang; Yuh-Lang Lee

    2007-01-01

    The present study demonstrates the creation of a stable, superhydrophobic surface by coupling of successive Langmuir-Blodgett (LB) depositions of micro- and nano-sized (1.5 µm\\/50 nm, 1.0 µm\\/50 nm, and 0.5 µm\\/50 nm) silica particles on a glass substrate with the formation of a self-assembled monolayer of dodecyltrichlorosilane on the surface of the particulate film. Particulate films, in which one layer

  19. Hollow organosilica nanospheres prepared through surface hydrophobic layer protected selective etching

    NASA Astrophysics Data System (ADS)

    Li, J.; Chen, L. X.; Li, X.; Zhang, C. C.; Zeng, F. L.

    2015-06-01

    In this study, a facile and effective surface hydrophobic layer protected selective etching strategy has been adopted to fabricate organic functionalized hollow silica nanospheres (OHSNSs). Our experiments demonstrated that the morphology and structure of OHSNSs were greatly affected by the types of organosilanes and concentrations of cetyltrimethylammonium bromide (CTAB) as pore-making agent. At low concentration of CTAB (1.9 mg/mL-1), it was found that the protective effect of the hydrophobic layer of 3-thiocyanatopropyltriethoxysilane (TCPTES) was so strong that can be endured long time etching (8 h), leading to the formation of hollow core and organic porous shell structure. And yet, the protective effect of the hydrophobic layer of vinyltriethoxysilane (VTES) was too weak to withstand alkali etching, resulting in preferentially etched of the outer vinyl protection shell. Whereas, at a higher concentration of CTAB (2.5 mg/mL-1), for TCPTES, the irregular and capsules-like spheres were obtained. In contrast, for VTES, porous core/solid shell structures with shell thickness of 16 nm were generated. In addition, no particles were observed when the CTAB concentration was above 2.5 mg/mL-1.

  20. Layer-by-layer assembled antisense DNA microsponge particles for efficient delivery of cancer therapeutics.

    PubMed

    Roh, Young Hoon; Lee, Jong Bum; Shopsowitz, Kevin E; Dreaden, Erik C; Morton, Stephen W; Poon, Zhiyong; Hong, Jinkee; Yamin, Inbar; Bonner, Daniel K; Hammond, Paula T

    2014-10-28

    Antisense oligonucleotides can be employed as a potential approach to effectively treat cancer. However, the inherent instability and inefficient systemic delivery methods for antisense therapeutics remain major challenges to their clinical application. Here, we present a polymerized oligonucleotides (ODNs) that self-assemble during their formation through an enzymatic elongation method (rolling circle replication) to generate a composite nucleic acid/magnesium pyrophosphate sponge-like microstructure, or DNA microsponge, yielding high molecular weight nucleic acid product. In addition, this densely packed ODN microsponge structure can be further condensed to generate polyelectrolyte complexes with a favorable size for cellular uptake by displacing magnesium pyrophosphate crystals from the microsponge structure. Additional layers are applied to generate a blood-stable and multifunctional nanoparticle via the layer-by-layer (LbL) assembly technique. By taking advantage of DNA nanotechnology and LbL assembly, functionalized DNA nanostructures were utilized to provide extremely high numbers of repeated ODN copies for efficient antisense therapy. Moreover, we show that this formulation significantly improves nucleic acid drug/carrier stability during in vivo biodistribution. These polymeric ODN systems can be designed to serve as a potent means of delivering stable and large quantities of ODN therapeutics systemically for cancer treatment to tumor cells at significantly lower toxicity than traditional synthetic vectors, thus enabling a therapeutic window suitable for clinical translation. PMID:25198246

  1. Surface pressure fluctuations in hypersonic turbulent boundary layers

    NASA Technical Reports Server (NTRS)

    Raman, K. R.

    1974-01-01

    The surface pressure fluctuations on a flat plate model at hypersonic Mach numbers of 5.2, 7.4 and 10.4 with an attached turbulent boundary layer were measured using flush mounted small piezoelectric sensors. A high frequency resolution of the pressure field was achieved using specially designed small piezoelectric sensors that had a good frequency response well above 300 KHz. The RMS pressures and non-dimensional energy spectra for all above Mach numbers are presented. The convective velocities, obtained from space time correlation considerations are equal to 0.7 U sub infinity. The results indicate the RMS pressures vary from 5 to 25 percent of the mean static pressures. The ratios of RMS pressure to dynamic pressure are less than the universally accepted subsonic value of 6 x 10/3. The ratio decreases in value as the Mach number or the dynamic pressure is increased. The ratio of RMS pressure to wall shear for Mach number 7.4 satisfies one smaller than or equal to p/tau sub w smaller than or equal to three.

  2. Interaction of laser-generated surface acoustic pulses with fine particles: Surface cleaning and adhesion studies

    NASA Astrophysics Data System (ADS)

    Kolomenskii, Al. A.; Schuessler, H. A.; Mikhalevich, V. G.; Maznev, A. A.

    1998-09-01

    The mechanical forces associated with the surface acceleration in high-amplitude surface acoustic waves (SAWs) detach the particles from the surface. The removal of micron sized particles with a nanosecond SAW pulse excited by a focused laser beam in a silicon wafer was quantitatively investigated. Both vertical and horizontal particle displacements have been observed. It is shown that for nanosecond SAW pulses the limit of the surface acceleration of about 1010m/s2 is set by the fracture of the material and corresponds to the removal of particles larger than about 0.05 ?m. In addition, the nonlinear transformation of the excited SAW pulses results in an increase of the surface acceleration and contributes to the cleaning process extending it to even smaller particle dimensions. The technique is applicable in vacuum and improves the energetic effectiveness of the cleaning due to the removal of particles not only in the irradiated region, but also in the wider area covered by the SAW pulse propagation. It can be also used for the determination of the Hamaker constant of the adhesion force.

  3. Laser-initiated anomalous diffusion of oxygen in a surface silicon layer enriched with defects

    Microsoft Academic Search

    A. F. Banishev; V. S. Golubev; A. Yu. Kremnev

    2000-01-01

    The effect of anomalously slow relaxation of deformation of silicon surface after laser stimulation is revealed and described.\\u000a This effect is attributed to “cold” diffusion of oxygen in the surface layer enriched with defects.

  4. First-order control of surface roughness at three scales: boundary layer dynamics, tracer dispersion and pebble abrasion

    NASA Astrophysics Data System (ADS)

    Jerolmack, D. J.; Litwin, K. L.; Phillips, C. B.; Martin, R. L.

    2012-12-01

    In many situations it may be appropriate to treat surfaces as smooth and particles as spherical, however here we focus on scenarios in which the roughness of the surface exerts a first-order control on flow and transport dynamics. We describe three vignettes at three different scales: (1) roughness transitions and resulting sediment transport dynamics over ~10-km distance in a desert dune field; (2) reach-scale river bed roughness and its influence on dispersion of tracer particles in bed load; and (3) the control of particle surface roughness on the nature and rate of pebble abrasion. For (1), we show how the abrupt transition from a flat surface to a dune field may be treated as a step increase in the aerodynamic roughness parameter - so long as the spatial scale considered is significantly larger than that of an individual dune. This increase causes a spatial decline in the boundary stress downwind that may be understood using simple boundary layer theory, resulting in a factor of three decrease in the sand flux over a distance of kilometers. For (2), laboratory and field studies of tracer particles in bed load indicate that they undergo short flights separated by long rest periods having a power-law tail - even in steady flows. We hypothesize that for near-threshold transport - which predominates is coarse-grained rivers - particles become trapped in 'wells' produced by surface roughness, and their rest time is controlled by the time for the surface to scour down and release them. Laboratory observations support this hypothesis, while comparison to non-geophysical 'flows' indicates that these dynamics are generic to transport in disordered systems. Finally, for (3) we report laboratory experiments by our group and others showing how abrasion rate decreases with decreasing particle roughness. Geometric models quantitatively support the intuition that locations of high positive curvature on pebble surfaces are more susceptible to abrasion; as they are preferentially removed, abrasion rates slow down accordingly.

  5. Study of liquid flows over solid surfaces by particle nanovelocimetry

    NASA Astrophysics Data System (ADS)

    Bouzigues, Cedric; Tabeling, Patrick

    2007-11-01

    In nanometric flows, interactions of the liquid with the surface become important. However, only indirect measurements of the slip length or the Debye length have been yet performed. Here we used near-field imaging of nanoparticles to observe water flows over solid surfaces. Water containing fluorescent nanoparticles was driven in microchannels and illuminated by an evanescent wave. Three-dimensional positioning of tracers allows the reconstruction of particle concentration and diffusion coefficient and of flow speed with 30 nm accuracy from 20 to 300 nm over the surface. We probed energy landscape over the surface which allows the first local in situ determination of surface potential and Debye length. We moreover directly measured slip length Ls. On hydrophilic surfaces, slippage is negligible but on smooth hydrophobic surface Ls=29+/-10 nm. This constitutes the first direct observation of slippage in a water flow. Altogether our results provide a novel insight into the behavior of fluids close of solid surfaces. The application of the tools we developed could be extended to study of composite surfaces and electro-osmotic flows.

  6. Intercalation-enhanced electric polarization and chain formation of nano-layered particles

    NASA Astrophysics Data System (ADS)

    Fossum, J. O.; Méheust, Y.; Parmar, K. P. S.; Knudsen, K. D.; Måløy, K. J.; Fonseca, D. M.

    2006-05-01

    Microscopy observations show that suspensions of synthetic and natural nano-layered smectite clay particles submitted to a strong external electric field undergo a fast and extended structuring. This structuring results from the interaction between induced electric dipoles, and is only possible for particles with suitable polarization properties. Smectite clay colloids are observed to be particularly suitable, in contrast to similar suspensions of a non-swelling clay. Synchrotron X-ray scattering experiments provide the orientation distributions for the particles. These distributions are understood in terms of competing i) homogenizing entropy and ii) interaction between the particles and the local electric field; they show that clay particles polarize along their silica sheet. Furthermore, a change in the platelet separation inside nano-layered particles occurs under application of the electric field, indicating that intercalated ions and water molecules play a role in their electric polarization. The resulting induced dipole is structurally attached to the particle, and this causes particles to reorient and interact, resulting in the observed macroscopic structuring. The macroscopic properties of these electro-rheological smectite suspensions may be tuned by controlling the nature and quantity of the intercalated species, at the nanoscale.

  7. Physiochemical Properties of Sodium Chloride Particles on Laboratory Ice Surfaces

    NASA Astrophysics Data System (ADS)

    Gleason, E. P.; Simpson, W. R.

    2013-12-01

    Aqueous halides (e.g. Cl- and Br-) on environmental ice surfaces are converted to reactive gases through heterogeneous chemistry that has broad consequences for springtime Arctic tropospheric oxidation chemistry. Recent studies indicate that atmospherically contaminated snow (e.g. more acidic snow) is more effective at activating halogens than frozen seawater. This study investigates the microstructure created by the addition of salts onto ice surfaces as a function of temperature. Microscopic sodium chloride salt crystals were labeled with a fluorescent dye (fluorescein) and placed onto laboratory ice surface below the hydrohalite (NaCl 2H2O)-water eutectic temperature. As temperature was increased above the eutectic, a discrete brine area formed around the crystal. Size and morphology of the brine area was determined using an Axioscope II epifluorescence microscope. Initially, the salt crystal did not entirely dissolve and three distinct phases (solid salt, brine, ice) were present for some time. Timescales for crystal dissolving, brine formation, and wetting across the ice surfaces where thus constrained. Similar experiments using a fluorescently labeled, laboratory-generated sea salt aerosol particles were also carried out and compared to the larger microscopic sodium chloride crystals. This work gives insight into how atmospheric particles deliver contaminants to ice surfaces, how those contaminants interact with ice surfaces and thus how they may impact halogen activation.

  8. Mechanisms for particle transfer and segregation in a turbulent boundary layer

    NASA Astrophysics Data System (ADS)

    Marchioli, Cristian; Soldati, Alfredo

    2002-10-01

    Particle transfer in the wall region of turbulent boundary layers is dominated by the coherent structures which control the turbulence regeneration cycle. Coherent structures bring particles toward and away from the wall and favour particle segregation in the viscous region, giving rise to non-uniform particle distribution profiles which peak close to the wall. The object of this work is to understand the reasons for higher particle concentration in the wall region by examining turbulent transfer of heavy particles to and away from the wall in connection with the coherent structures of the boundary layer. We will examine the behaviour of a dilute dispersion of heavy particles flyashes in air in a vertical channel flow, using pseudo-spectral direct numerical simulation to calculate the turbulent flow field at a shear Reynolds number Re[tau] = 150, and Lagrangian tracking to describe the dynamics of particles. Drag force, gravity and Saffman lift are used in the equation of motion for the particles, which are assumed to have no influence on the flow field. Particle interaction with the wall is fully elastic. As reported in several previous investigations, we found that particles are transferred by sweeps Q2 type events in the wall region, where they preferentially accumulate in the low-speed streak environments, whereas ejections Q4 type events transfer particles from the wall region to the outer flow. We quantify the efficiency of the instantaneous realizations of the Reynolds stresses events in transferring different size particles to the wall and away from the wall, respectively. Our findings confirm that sweeps and ejections are efficient transfer mechanisms for particles. In particular, we find that only those sweep and ejection events with substantial spatial coherence are effective in transferring particles. However, the efficiency of the transfer mechanisms is conditioned by the presence of particles to be transferred. In the case of ejections, particles are more rarely available since, when in the viscous wall layer, they are concentrated under the low-speed streaks. Even though the low-speed streaks are ejection-like environments, particles remain trapped for a long time. This phenomenon, which causes accumulation of particles in the near-wall region, can be interpreted in terms of overall fluxes toward and away from the wall by the theory of turbophoresis. This theory, proposed initially by Caporaloni et al. (1975) and re-examined later by Reeks (1983), can help to explain the existence of net particle fluxes toward the wall as a manifestation of the skewness in the velocity distribution of the particles (Reeks 1983). To understand the local and instantaneous mechanisms which give rise to the phenomenon of turbophoresis, we focus on the near-wall region of the turbulent boundary layer. We examine the role of the rear-end of a quasistreamwise vortex very near to the wall in preventing particles in the proximity of the wall from being re-entrained by the pumping action of the large, farther from the wall, forward-end of a following quasi-streamwise vortex. We examine several mechanisms for turbulence structures near the wall and we find that the mechanism based on the archetypal quasi-streamwise structures identified by Schoppa & Hussain (1997), the parent offspring regeneration cycle for near-wall quasi-streamwise vortices discussed by Brooke & Hanratty (1993), and the mechanism based on coherent packets of hairpin vortices, the fundamental super-structure characterized by Adrian, Meinhart & Tomkins (2000), all depict the same characteristic pattern which is responsible for particle trapping very near to the wall.

  9. Acoustic characterization of thin polymer layers for Love mode surface acoustic waveguide

    Microsoft Academic Search

    L. El Fissi; J.-M. Friedt; S. Ballandras; L. Robert; F. Cherioux

    2008-01-01

    Beyond the great gravimetric sensitivity provided by the polymer guiding layer of shear surface wave on quartz resulting from a low acoustic velocity, the use of photo resists provide economical means of depositing guiding layers of optimal thicknesses compared to inorganic layer deposition processes (typically PECVD deposition of silicon dioxide lasting several hours). We here analyze the evolution of the

  10. Particle resuspension and associated coherent structures in a turbulent boundary layer

    Microsoft Academic Search

    David Alan Braaten

    1988-01-01

    Fundamental properties of particle resuspension from a surface solely by turbulent fluid forces was examined experimentally by observing intermittent particle resuspension and associated turbulent flow properties. Experiments were conducted in an environmental wind tunnel, where sparse beds of monodisperse Lycopodium spores (Club Moss) were placed flush with the floor of the wind tunnel, and exposed to a steady, well developed

  11. Explosive particle soil surface dispersion model for detonated military munitions.

    PubMed

    Hathaway, John E; Rishel, Jeremy P; Walsh, Marianne E; Walsh, Michael R; Taylor, Susan

    2015-07-01

    The accumulation of high explosive mass residue from the detonation of military munitions on training ranges is of environmental concern because of its potential to contaminate the soil, surface water, and groundwater. The US Department of Defense wants to quantify, understand, and remediate high explosive mass residue loadings that might be observed on active firing ranges. Previously, efforts using various sampling methods and techniques have resulted in limited success, due in part to the complicated dispersion pattern of the explosive particle residues upon detonation. In our efforts to simulate particle dispersal for high- and low-order explosions on hypothetical firing ranges, we use experimental particle data from detonations of munitions from a 155-mm howitzer, which are common military munitions. The mass loadings resulting from these simulations provide a previously unattained level of detail to quantify the explosive residue source-term for use in soil and water transport models. In addition, the resulting particle placements can be used to test, validate, and optimize particle sampling methods and statistical models as applied to firing ranges. Although the presented results are for a hypothetical 155-mm howitzer firing range, the method can be used for other munition types once the explosive particle characteristics are known. PMID:26050065

  12. The Point of Departure of a Particle Sliding on a Curved Surface

    ERIC Educational Resources Information Center

    Aghamohammadi, Amir

    2012-01-01

    A particle is thrown tangentially on a surface. It is shown that for some surfaces and for special initial velocities the thrown particle immediately leaves the surface, and for special conditions it never leaves the surface. The conditions for leaving the surface are investigated. The problem is studied for a surface with the cross-section y =…

  13. Turbulent structure of scalars in the eddy surface layer over land and sea

    NASA Astrophysics Data System (ADS)

    Smedman, Ann-Sofi; Sahlee, Erik

    2015-04-01

    Turbulent structure of scalars in the 'eddy surface layer' over land and sea. 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 (eddy surface layer), especially the shape of the spectra of the wind components and corresponding fluxes. However, the structure of temperature and humidity fluctuations in the eddy surface layer shows quite different behaviour. In particular the efficiency of turbulent exchange of sensible and latent heat is observed to be more strongly enhanced than is consistent with standard similarity theory. Also the profiles of dissipation of turbulent kinetic energy and temperature fluctuation variance are found to depend on the height of the eddy surface layer and not the height above the surface. All these features are found to be similar in measurements at a marine site, a flat land site and during hurricane conditions (hurricane Fabian and Isabel). 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.

  14. Oscillating bubble SHG on surface elastic and surface viscoelastic systems: new insights in the dynamics of adsorption layers.

    PubMed

    Andersen, A; Oertegren, J; Koelsch, P; Wantke, D; Motschmann, H

    2006-09-21

    Surface rheology governs a great variety of interfacial phenomena such as foams or emulsions and plays a dominant role in several technological processes such as high-speed coating. Its major difference with bulk rheology resides in the high compressibility of the surface phase, which is the direct consequence of the molecular exchange between adsorbed and dissolved species. In analogy to bulk rheology, a complex surface dilational modulus, epsilon, which captures surface tension changes upon defined area changes of the surface layer, can be defined. The module epsilon is complex, and the molecular interpretation of the dissipative process that gives rise to the imaginary part of the module is subject to some controversy. In this contribution, we used the oscillating bubble technique to study the surface dilational modulus in the mid-frequency range. The dynamic state of the surface layer was monitored by a pressure sensor and by surface second-harmonic generation (SHG). The pressure sensor measures the real and imaginary part of the modulus while SHG monitors independently the surface composition under dynamic conditions. The experiment allows the assessment of the contribution of the compositional term to the surface dilational modulus epsilon. Two aqueous surfactant solutions have been characterized: a surface elastic and a surface viscoelastic solution. The elastic surface layer can be described within the framework of the extended Lucassen-van den Tempel Hansen model. The change in surface concentration is in phase with the relative area change of the surface layer, which is in strong contrast with the results obtained from the surface viscoelastic solution. Here, surface tension, area change, and surface composition are phase-shifted, providing evidence for a nonequilibrium state within the surface phase. The data are used to assess existing surface rheology models. PMID:16970473

  15. High-Speed Transport of Fluid Drops and Solid Particles via Surface Acoustic Waves

    NASA Technical Reports Server (NTRS)

    Bar-Cohen, Yoseph; Bao, Xiaoqi; Sherrit, Stewart; Badescu, Mircea; Lih, Shyh-shiuh

    2012-01-01

    A compact sampling tool mechanism that can operate at various temperatures, and transport and sieve particle sizes of powdered cuttings and soil grains with no moving parts, has been created using traveling surface acoustic waves (SAWs) that are emitted by an inter-digital transducer (IDT). The generated waves are driven at about 10 MHz, and it causes powder to move towards the IDT at high speed with different speeds for different sizes of particles, which enables these particles to be sieved. This design is based on the use of SAWs and their propelling effect on powder particles and fluids along the path of the waves. Generally, SAWs are elastic waves propagating in a shallow layer of about one wavelength beneath the surface of a solid substrate. To generate SAWs, a piezoelectric plate is used that is made of LiNbO3 crystal cut along the x-axis with rotation of 127.8 along the y-axis. On this plate are printed pairs of fingerlike electrodes in the form of a grating that are activated by subjecting the gap between the electrodes to electric field. This configuration of a surface wave transmitter is called IDT. The IDT that was used consists of 20 pairs of fingers with 0.4-mm spacing, a total length of 12.5 mm. The surface wave is produced by the nature of piezoelectric material to contract or expand when subjected to an electric field. Driving the IDT to generate wave at high amplitudes provides an actuation mechanism where the surface particles move elliptically, pulling powder particles on the surface toward the wavesource and pushing liquids in the opposite direction. This behavior allows the innovation to separate large particles and fluids that are mixed. Fluids are removed at speed (7.5 to 15 cm/s), enabling this innovation of acting as a bladeless wiper for raindrops. For the windshield design, the electrodes could be made transparent so that they do not disturb the driver or pilot. Multiple IDTs can be synchronized to transport water or powder over larger distances. To demonstrate the transporting action, a video camera was used to record the movement. The speed of particles was measured from the video images.

  16. Effective surface modification by stimuli-responsive polymers onto the magnetite nanoparticles by layer-by-layer method

    Microsoft Academic Search

    Kazuya Yamamoto; Daisuke Matsukuma; Kazuyuki Nanasetani; Takao Aoyagi

    2008-01-01

    Effective surface modification of poly(N-isopropylacrylamide)-based temperature-responsive polymers onto the magnetite nanoparticles was investigated. To achieve this purpose, layer-by-layer method was applied. This technique is based on sequential chemical reactions between the temperature-responsive polymers with carboxyl groups and other another polymers with amino groups. After the polyion complex formation, carbodiimide chemistry was used to cross-link both the functional polymers. As a

  17. Antimicrobial and antioxidant surface modification of cellulose fibers using layer-by-layer deposition of chitosan and lignosulfonates.

    PubMed

    Li, Hui; Peng, Lincai

    2015-06-25

    To confer cellulose fibers antimicrobial and antioxidant activities, chitosan (CS)/lignosulfonates (LS) multilayers were constructed on fibers surfaces through layer-by-layer deposition technique. The formation of CS/LS multilayers on cellulose fibers surfaces was verified by X-ray photoelectron spectroscopy (XPS) and zeta potential measurement. The surface morphologies of CS/LS multilayers on fibers surfaces were observed by atomic force microscopy (AFM). The results showed that characteristic element (i.e. N and S element) content increased with increasing bilayers number, the surface LS content increased linearly as a function of bilayers. Zeta potential of modified fibers was inversed after deposition of each layer. AFM phase images indicated that the cellulose microfibrils on fibers surfaces were gradually covered by granular LS aggregate. The antimicrobial testing results demonstrated that CS/LS multilayers modified fibers with CS in the outermost layer exhibited higher antimicrobial activity against Escherichia coli. The antioxidant testing results showed that antioxidant activity of CS/LS multilayers modified fibers was better than that of original fibers under the same oxidation conditions. PMID:25839791

  18. Boundary-layer receptivity due to distributed surface imperfections of a deterministic or random nature

    Microsoft Academic Search

    Meelan Choudhari

    1992-01-01

    Acoustic receptivity of a Blasius boundary layer in the presence of distributed surface irregularities is investigated analytically. It is shown that, out of the entire spatial spectrum of the surface irregularities, only a small band of Fourier components can lead to an efficient conversion of the acoustic input at any given frequency to an unstable eigenmode of the boundary layer

  19. Boundary-layer receptivity due to distributed surface imperfections of a deterministic or random nature

    Microsoft Academic Search

    Meelan Choudhari

    1993-01-01

    Acoustic receptivity of a Blasius boundary layer in the presence of distributed, two-dimensional surface irregularities is investigated analytically. It is shown that, out of the entire spatial spectrum of the surface irregularities, only a narrow band of Fourier components can lead to an efficient conversion of the acoustic input at any given frequency to an unstable eigenmode of the boundary-layer

  20. A statistical model for variability of the Arctic Ocean surface layer salinity1 Ekaterina Chernyavskaya1

    E-print Network

    A statistical model for variability of the Arctic Ocean surface layer salinity1 2 Ekaterina email: sudakov@math.utah.edu12 13 Abstract14 Significant salinity anomalies were observed in the Arctic Ocean surface layer during the last15 decade. On the base of gridded data of winter salinity

  1. Enhancement of Bovine Bone Ablation Assisted by a Transparent Liquid Layer on a Target Surface

    Microsoft Academic Search

    Hyun Wook Kang; Ho Lee; Shaochen Chen; Ashley J. Welch

    2006-01-01

    The purpose of this study was to investigate the laser- induced ablation of bovine bone assisted by a transparent liquid layer on top of the target surface. A Q-switched Nd:YAG laser was used to ablate bovine tibia at various energy levels. Distilled water was applied to the sample surface in order to examine the role of a transparent liquid layer

  2. Massless and massive particle-in-a-box states in single- and bi-layer graphene

    Microsoft Academic Search

    Sungjae Cho; Michael Fuhrer

    2011-01-01

    Electron transport through short, phase-coherent metal-graphene-metal devices occurs via resonant transmission through particle-in-a-box-like\\u000a states defined by the atomically-sharp metal leads. We study the spectrum of particle-in-a-box states for single- and bi-layer\\u000a graphene, corresponding to massless and massive two-dimensional (2-D) fermions. The density of states D as a function of particle number n shows the expected relationships D(n) ? n\\u000a 1\\/2

  3. Effects on a sheet surface of an erosive particle jet upon impact

    Microsoft Academic Search

    P Chevallier; A. B Vannes

    1995-01-01

    The impact of particles on a surface can cause severe erosion damage. The erosion of a surface by abrasive particles in an inert fluid should depend on the number of particles striking the surface, their velocity and their direction relative to the surface. These quantities are largely determined by the flow conditions.The importance of knowledge of the flow field surrounding

  4. Evaluation of active layer properties and charge collection efficiency of GaAs particle detectors

    Microsoft Academic Search

    J. W. Chen; T. Frömmichen; J. Ludwig; M. Kohler; T. Plötze; M. Rogalla; K. Runge; D. G. Ebling; M. Fiederle; P. Hug

    1995-01-01

    According to Ramo's theorem the charge collection efficiency of a particle detector is mainly influenced by the field distribution between the contacts of a Schottky diode. In semi-insulating GaAs material a space charge layer is formed due to deep levels needed for the compensation of acceptors. In this paper the deep levels and their influence on the distribution of the

  5. Incipient motion of a small particle in the viscous boundary layer at a pipe wall

    Microsoft Academic Search

    P Stevenson; R. B Thorpe; J. F Davidson

    2002-01-01

    A force balance is derived for a hemispherical particle in the viscous boundary layer at the wall of a horizontal pipe conveying Newtonian fluid; the hemisphere, of radius much less than that of the pipe, rests on the bottom with its flat face against the wall. The drag on the hemisphere is calculated from the creeping flow field of Price

  6. Surface and sub-surface reactions during low temperature aluminium oxide atomic layer deposition on fiber-forming polymers

    E-print Network

    Khan, Saad A.

    , but the coating structure depends strongly on the starting polymer composition. For the weakly interacting interactions between depositing species and the polymer surface or chain.7­11 While studies addressingSurface and sub-surface reactions during low temperature aluminium oxide atomic layer deposition

  7. Use of a High-Resolution Sodar to Study Surface-layer Turbulence at Night

    Microsoft Academic Search

    Stefania Argentini; Giangiuseppe Mastrantonio; Igor Petenko; Ilaria Pietroni; Angelo Viola

    2011-01-01

    Measurements in the atmospheric surface layer are generally made with point sensors located in the first few tens of metres.\\u000a In most cases, however, these measurements are not representative of the whole surface layer. Standard Doppler sodars allow\\u000a a continuous display of the turbulent thermal structure and wind profiles in the boundary layer up to 1000 m, with a few

  8. Effective surface viscosities of a particle-laden fluid interface.

    PubMed

    Lishchuk, S V; Halliday, I

    2009-07-01

    The Einstein formula for the effective shear viscosity of low Reynolds number suspension flows is generalized to the case of flat, low-concentration, particle-laden interfaces separating two immiscible fluids. The effective surface shear and dilational viscosities of this system is found to be eta{s}=5/3(eta{1}+eta{2})R phi and zeta{s}=5(eta_{1}+eta_{2})R phi , correspondingly, where eta{1} and eta{2} are the shear viscosities of two bulk fluids and phi is the surface concentration of spherical particles of radius R . The formula is found to be in excellent agreement with data obtained using multicomponent lattice Boltzmann equation simulation. PMID:19658805

  9. Tokamak dust particle size and surface area measurement

    SciTech Connect

    Carmack, W.J.; Smolik, G.R.; Anderl, R.A.; Pawelko, R.J.; Hembree, P.B.

    1998-07-01

    The INEEL has analyzed a variety of dust samples from experimental tokamaks: General Atomics` DII-D, Massachusetts Institute of Technology`s Alcator CMOD, and Princeton`s TFTR. These dust samples were collected and analyzed because of the importance of dust to safety. The dust may contain tritium, be activated, be chemically toxic, and chemically reactive. The INEEL has carried out numerous characterization procedures on the samples yielding information useful both to tokamak designers and to safety researchers. Two different methods were used for particle characterization: optical microscopy (count based) and laser based volumetric diffraction (mass based). Surface area of the dust samples was measured using Brunauer, Emmett, and Teller, BET, a gas adsorption technique. The purpose of this paper is to present the correlation between the particle size measurements and the surface area measurements for tokamak dust.

  10. Importance of boundary layer entrainment for surface fluxes over land

    NASA Astrophysics Data System (ADS)

    McGrath-Spangler, Erica L.

    An idealized experiment examined the impacts of entrainment in a coupled ecosystem-atmosphere model by implementing an enhanced entrainment parameterization based on the assumption that the heat flux at the top of the PBL is negatively proportional to the heat flux at the surface. This experiment found that entrainment produced a warmer, drier, and deeper PBL and that the surface fluxes of heat and moisture were modified by the vegetative response to the altered atmospheric conditions. A realistic simulation for the summer of 1999 found that enhanced entrainment produced stronger early morning growth of the PBL and a deeper midday depth. This better captured the monthly mean diurnal cycle of PBL depth from observations by a radar sounding system in northern Wisconsin. Additionally, the complex land-atmosphere interactions produced a time-mean spatial CO 2 gradient of 7 ppm over 1000 km. A sensitivity analysis performed for June 2007 to the strength of the PBL-top entrainment flux found subtle spatial variations in the time mean. The addition of entrainment from overshooting thermals weakened the Bermuda high circulation and weakened the spatial gradients between the warm, dry semiarid southwestern United States and cooler, moister locations in eastern North America. These subtle variations produced a 3.5 ppm CO2 change in the time mean across 280 km. One possible explanation for these more subtle results is that additional changes to the coupled model resulted in persistent cloud cover that produced relatively cold and dark conditions. In order to evaluate and improve model simulations, PBL depth has been estimated using the backscatter from the LIDAR onboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite. Using an automated method, millions of estimates have been derived to which model results can be compared. This method evaluates the maximum vertical variance of the backscatter in order to identify backscatter features associated with the top of the PBL and helps to identify the vertical extent of turbulent mixing. This analysis sheds some light on the spatial heterogeneity of boundary layer processes. The derived depths are shallower over water than over land and show a local minimum along the Mississippi River valley. Deeper features are found over the desert Southwest and deeper than expected values are retrieved over the Boreal forests.

  11. Surface Layer Investigation of a Shot-Peened Duplex Stainless Steel Utilizing X-ray Diffraction

    NASA Astrophysics Data System (ADS)

    Feng, Qiang; Wu, Xueyan; Jiang, Chuanhai; Xu, Zhou; Wu, Lihong

    2013-07-01

    Distributions of residual stresses and microstructure in the surface layers of shot-peened duplex stainless steel (DSS) S32205 were investigated. The results reveal that both compressive residual stresses (CRS) and microhardness increase with the enhancement of shot-peening (SP) intensity in the surface deformation layers. The maximum value of CRS of ferrite lies in the surface layer but that of austenite locates below the surface layer after SP. SP influence on the microstructure of DSS was studied using x-ray diffraction profiles, and the domain size and microstrain were calculated via Voigt method. After SP, the domain sizes are refined, and microstrain becomes severe at surface layers in both phases. On comparing the calculated results, it is found that the more evident domain size subdivision and the more serious microstrain increase in austenite than those in ferrite are due to the higher work hardening of austenite.

  12. Particle scale modeling of material removal and surface roughness in chemical mechanical polishing

    NASA Astrophysics Data System (ADS)

    Yeruva, Suresh Babu

    2005-11-01

    Chemical mechanical polishing (CMP) is widely adopted in producing excellent local and global planarization of microelectronic devices. It has been demonstrated experimentally that the polishing performance is a result of the synergistic effect of both the chemicals and the particles involved in CMP. However, the fundamental mechanisms of material removal and the interactions of the chemical and mechanical effects are not well understood. A comprehensive model for CMP was developed taking into account both the chemical and mechanical effects for slurries with a given particle size distribution. The model developed (PERC II) is based on a previously developed model (PERC I). The chemical aspect is attributed to the chemical modification of the surface layer due to slurry chemistry, whereas the mechanical aspect is incorporated by indentation of particles into the modified layer and the substrate depending on the operating conditions. In this study, the effects of particle size and pad asperity distributions are included in the model. The contact area of pad with wafer was measured in dry and wet conditions in different pH solutions using optical microscopy and Fourier transform infrared spectroscopy respectively. Pad surface mechanical properties in dry and wet states were also investigated using atomic force microscopy. The contact area results obtained were utilized in modeling to estimate the pad modulus leading to pad-wafer contact stress distribution. The predictions of the model show a reasonable agreement with the experimental data. The model is validated for oxide and metal CMP systems. The PERC II model not only predicts the overall removal rate, but also the surface roughness of the polished wafer in selected systems. The developed model can be used to optimize the current CMP systems and provide insights into future CMP endeavors.

  13. Effective surface viscosities of a particle-laden fluid interface

    Microsoft Academic Search

    S. V. Lishchuk; I. Halliday

    2009-01-01

    The Einstein formula for the effective shear viscosity of low Reynolds number suspension flows is generalized to the case of flat, low-concentration, particle-laden interfaces separating two immiscible fluids. The effective surface shear and dilational viscosities of this system is found to be etas=(5)\\/(3)(eta1+eta2)Rvarphi and zetas=5(eta1+eta2)Rvarphi , correspondingly, where eta1 and eta2 are the shear viscosities of two bulk fluids and

  14. Airborne observations of new particle formation events in the boundary layer using a Zeppelin

    NASA Astrophysics Data System (ADS)

    Lampilahti, Janne; Manninen, Hanna E.; Nieminen, Tuomo; Mirme, Sander; Pullinen, Iida; Yli-Juuti, Taina; Schobesberger, Siegfried; Kangasluoma, Juha; Kontkanen, Jenni; Lehtipalo, Katrianne; Ehn, Mikael; Mentel, Thomas F.; Petäjä, Tuukka; Kulmala, Markku

    2014-05-01

    Atmospheric new particle formation (NPF) is a frequent and ubiquitous process in the atmosphere and a major source of newly formed aerosol particles [1]. However, it is still unclear how the aerosol particle distribution evolves in space and time during an NPF. We investigated where in the planetary boundary layer does NPF begin and how does the aerosol number size distribution develop in space and time during it. We measured in Hyytiälä, southern Finland using ground based and airborne measurements. The measurements were part of the PEGASOS project. NPF was studied on six scientific flights during spring 2013 using a Zeppelin NT class airship. Ground based measurements were simultaneously conducted at SMEAR II station located in Hyytiälä. The flight profiles over Hyytiälä were flown between sunrise and noon during the growth of the boundary layer. The profiles over Hyytiälä covered vertically a distance of 100-1000 meters reaching the mixed layer, stable (nocturnal) boundary layer and the residual layer. Horizontally the profiles covered approximately a circular area of four kilometers in diameter. The measurements include particle number size distribution by Neutral cluster and Air Ion Spectrometer (NAIS), Differential Mobility Particle Sizer (DMPS) and Particle Size Magnifier (PSM) [2], meteorological parameters and position (latitude, longitude and altitude) of the Zeppelin. Beginning of NPF was determined from an increase in 1.7-3 nm ion concentration. Height of the mixed layer was estimated from relative humidity measured on-board the Zeppelin. Particle growth rate during NPF was calculated. Spatial inhomogeneities in particle number size distribution during NPF were located and the birthplace of the particles was estimated using the growth rate and trajectories. We observed a regional NPF event that began simultaneously and evolved uniformly inside the mixed layer. In the horizontal direction we observed a long and narrow high concentration plume of growing particles that moved over the measurement site. The particles of the regional event as well as the particles of the plume were uniformly distributed in the vertical direction and showed a similar growth rate of approximately 2 nm/h. The plume caused sharp discontinuities in the number size distribution of the growing particle mode. These kinds of discontinuities are seen quite often on SMEAR II data during NPF events and it is likely that they are caused by inhomogeneous NPF in the horizontal direction (possibly narrow long plumes). This work is supported by European Commission under the Framework Programme 7 (FP7-ENV-2010-265148) and by the Academy of Finland Centre of Excellence program (project no. 1118615). The Zeppelin is accompanied by an international team of scientists and technicians. They are all warmly acknowledged. References [1] Kulmala, M., et al., (2013), Direct Observations of Atmospheric Aerosol Nucleation, Science, 339, 943-946 [2] Kulmala, M., et al., (2012), Measurement of the nucleation of atmospheric aerosol particles, Nature Protocols, 7, 1651-1667

  15. Wall Shear stress measurements in the atmosperhic surface layer

    E-print Network

    Marusic, Ivan

    was to further understand similarities that may exist between the SLTEST sur- face layer and the wind tunnel]. The geophysically driven air flow is therefore thought to share im- portant characteristics with common wind-tunnel boundary layers, albeit at three orders of magnitude higher Reynolds number. Thus, another goal

  16. ELECTROSTATIC SURFACE STRUCTURES OF COAL AND MINERAL PARTICLES

    SciTech Connect

    NONE

    1998-12-01

    It is the purpose of this research to study electrostatic charging mechanisms related to electrostatic beneficiation of coal with the goal of improving models of separation and the design of electrostatic separators. Areas addressed in this technical progress report are (a) electrostatic beneficiation of Pittsburgh #8 coal powders as a function of grind size and processing atmosphere; (b) the use of fluorescent micro-spheres to probe the charge distribution on the surfaces of coal particles; (c) the use of electrostatic beneficiation to recover unburned carbon from flyash; (d) the development of research instruments for investigation of charging properties of coal. Pittsburgh #8 powders were beneficiated as a function of grind size and under three atmosphere conditions: fresh ground in air , after 24 hours of air exposure, or under N2 atmosphere. The feed and processed powders were analyzed by a variety of methods including moisture, ash, total sulfur, and pyritic sulfur content. Mass distribution and cumulative charge of the processed powders were also measured. Fresh ground coal performed the best in electrostatic beneficiation. Results are compared with those of similar studies conducted on Pittsburgh #8 powders last year (April 1, 1997 to September 30, 1997). Polystyrene latex spheres were charged and deposited onto coal particles that had been passed through the electrostatic separator and collected onto insulating filters. The observations suggest bipolar charging of individual particles and patches of charge on the particles which may be associated with particular maceral types or with mineral inclusions. A preliminary investigation was performed on eletrostatic separation of unburned carbon particles from flyash. Approximately 25% of the flyash acquired positive charge in the copper tribocharger. This compares with 75% of fresh ground coal. The negatively charged material had a slightly reduced ash content suggesting some enrichment of carbonaceous material. There was also evidence that the carbon is present at a higher ratio in larger particles than in small particles. An ultraviolet photoelectron counter for use in ambient atmosphere is nearing completion. The counter will be used to measure work functions of different maceral and mineral types in the coal matrix. A Particle Image Analyzer for measuring size and charge of airborne particles is also under contruction and its current status is presented. A charged, monodisperse, droplet generator is also being constructed for calibration of the Particle Image Analyzer and other airborne particle analyzers in our labs.

  17. FTIR external reflection study of surface layers on coal

    SciTech Connect

    Mielczarski, J.A.; Yordan, J.L.; Yoon, R.H.

    1988-01-01

    An infrared reflection-absorption spectroscopy (IRAS) technique has been developed to study the structure of adsorbed surfactant layers on coal. Owing to the optical properties of coal, negative as well as positive absorption bands are observed in the recorded spectra which depend on the angle of incidence (/theta/) and the polarization of the incident radiation. Theoretical calculations make it possible to predict the changes in absorbance with /theta/ and polarization. These changes are a function of the optical properties of the coal and the adsorption layer. The application of the IRAS method to studies of the adsorption layer is presented for several systems, i.e., adsorption of sodium laurate and a nonionic surfactant on coal. In addition, the oxidation layer produced during low-temperature oxidation of coal has been investigated. The results obtained indicate that the IRAS method has an enormous potential for use in determining the structure of an adsorption layer on coal after different treatments.

  18. Bragg resonances of magnetostatic surface spin waves in a layered structure: Magnonic crystal-dielectric-metal

    NASA Astrophysics Data System (ADS)

    Beginin, E. N.; Filimonov, Yu. A.; Pavlov, E. S.; Vysotskii, S. L.; Nikitov, S. A.

    2012-06-01

    It is experimentally shown that metal cladding of the surface of a one-dimensional magnonic crystal destroys the Bragg band gaps in microwave transmission spectra of propagating magnetostatic surface spin waves in magnonic crystal. This is a consequence of violating a phase synchronism condition of forward and reflected by a magnonic crystal magnetostatic surface wave. When a magnetostatic surface wave propagates in a layered structure, ferromagnetic film with a magnonic crystal-dielectric layer-metal cladding this synchronism condition can also be fulfilled, not depending on the thickness of a dielectric layer.

  19. Surface Modification of Layered Zirconium Phosphates: A Novel Pathway to Multifunctional Nanomaterials 

    E-print Network

    Mosby, Brian Matthew

    2014-04-08

    was investigated with a variety of coupling agents. Initially, covalent attachment of molecules to the exterior surface of the nano particles was attempted with silanes and epoxides. Subsequently, the ion exchange character of the surface phosphate groups was used...

  20. Surface Modification of Layered Zirconium Phosphates: A Novel Pathway to Multifunctional Nanomaterials

    E-print Network

    Mosby, Brian Matthew

    2014-04-08

    was investigated with a variety of coupling agents. Initially, covalent attachment of molecules to the exterior surface of the nano particles was attempted with silanes and epoxides. Subsequently, the ion exchange character of the surface phosphate groups was used...

  1. Particle deposition on superhydrophobic surfaces by sessile droplet evaporation

    NASA Astrophysics Data System (ADS)

    Dicuangco, Mercy Grace

    Prediction and active control of the spatial distribution of particulate deposits obtained from sessile droplet evaporation is essential in ink-jet printing, nanostructure assembly, biotechnology, and other applications that require localized deposits. In recent years, sessile droplet evaporation on bio-inspired superhydrophobic surfaces has become an attractive method for depositing materials on a site-specific, localized region, but is less explored compared to evaporative deposition on hydrophilic surfaces. It is therefore of interest to understand particle deposition during droplet evaporation on superhydrophobic surfaces to enable accurate prediction and tunable control of localized deposits on such surfaces. The purpose of the present work is to explore the morphology of particles deposited on superhydrophobic surfaces by the evaporation of sessile water droplets containing suspended latex spheres. Droplet evaporation experiments are performed on non-wetting, textured surfaces with varying geometric parameters. The temporal evolution of the droplet contact radius and contact angle throughout the evaporation process are tracked by visualizing the transient droplet shape and wetting behavior. The droplets are observed to exhibit a combination of the following modes of evaporation: the constant contact radius mode, the constant contact angle mode, and the mixed mode in which the contact angle and the contact radius change simultaneously. After complete dry-out, the remaining particulate deposits are qualitatively and quantitatively characterized to describe their spatial distribution. In the first part of the study, the test surfaces are maintained at different temperatures. Experiments are conducted at ambient conditions and at elevated substrate temperatures of approximately 40°C, 50°C, and 60°C. The results show that droplet evaporation on superhydrophobic surfaces, driven by either mass diffusion at ambient conditions or by substrate heating, suppresses deposition of particles at the contact-line during droplet evaporation. This behavior provides an effective means of localizing the deposition of suspended particles. In the second part of the study, the droplets are allowed to evaporate at ambient conditions on test substrates with significant relative differences in surface morphology. These differing surfaces yield a wide range of surface wettability as a means to control the particulate deposition process. Analysis of the droplet wetting behavior throughout the evaporation process show that the droplet could either remain in the Cassie state (resting on top of the roughness elements) or transition into the Wenzel state (roughness elements flooded). Top- and side-view images of the droplet profile are visualized to confirm the droplet wetting state near the end of evaporation. Experimental observations are compared with a theoretical trend of the Cassie-to-Wenzel transition based on the capillary-Laplace pressure balance at transition between wetting states. The results reveal a relationship between localized deposit size and surface morphology based on this ultimate wetting state. An optimum surface morphology for minimizing the deposit coverage area is identified.

  2. Boundary layers in a dilute particle suspension M.R. Foster, P.W. Duck and R.E. Hewitt

    E-print Network

    Heil, Matthias

    Boundary layers in a dilute particle suspension M.R. Foster, P.W. Duck and R.E. Hewitt 2006 MIMS;Boundary layers in a dilute particle suspension BY M. R. FOSTER 1 , P. W. DUCK 2, * AND R. E. HEWITT 2 1

  3. Integration of satellite and surface data using a radiative-convective oceanic boundary-layer model

    NASA Technical Reports Server (NTRS)

    Betts, Alan K.; Minnis, Patrick; Ridgway, W.; Young, David F.

    1992-01-01

    A mixing-line boundary-layer model is used to retrieve cloud-top height from satellite-derived cloud-top temperatures, using 700-hPa National Meteorological Center (NMC) analyses and the Comprehensive Ocean and Atmosphere Data Set (COADS) surface data as supporting datasets. Results are compared with the fixed-lapse-rate method of retrieving boundary-layer depth from sea surface temperatures (SST) and cloud-top temperatures. A radiative-convective equilibrium boundary-layer model is used to retrieve boundary-layer structure given SST and surface wind, satellite cloud-top temperatures and cloud fraction, and the 700-hPa NMC thermodynamic analyses. Good agreement is found between the COADS data and the model solutions for low-level temperature and moisture. This suggests that equilibrium boundary-layer models may be of use over remote oceans in the retrieval of boundary-layer structure.

  4. Fretting wear behavior of nanocrystalline surface layer of copper under dry condition

    Microsoft Academic Search

    Y. S. Zhang; Z. Han; K. Lu

    2008-01-01

    Unlubricated fretting tests were performed with a nanocrystalline surface layer of a 99.99wt.% copper fabricated by means of surface mechanical attrition treatment (SMAT), in comparison with a coarse-grained (CG) copper. The measured friction and wear data show that the fretting wear resistance is markedly enhanced with the nanocrystalline surface layer relative to the CG counterpart. The friction coefficient and wear

  5. Surface coating for flame retardant behavior of cotton fabric by layer-by-layer processing

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Flame retardant behavior has been prepared by the layer-by layer assemblies of branched polyethylenimine (BPEI), kaolin, urea, diammonium phosphate (dibasic) on cotton fabrics. Three different kinds of cotton fabrics (print cloth, mercerized print cloth, and mercerized twill fabric) were prepared wi...

  6. Analysis of strain transfer of six-layer surface-bonded fiber Bragg gratings.

    PubMed

    Wang, Quan-bao; Qiu, Ye; Zhao, Hai-tao; Chen, Ji-an; Wang, Yue-ying; Fan, Zhen-min

    2012-06-20

    A theoretical analysis of strain transfer of six-layer surface-bonded fiber Bragg gratings (FBGs) subjected to uniform axial stress is presented. The proposed six-layer structure consists of optical fiber, protective coating, adhesive layer, substrate layer, outer adhesive layer, and host material, which is different from the four-layer case of common acknowledgement. A theoretical formula of strain transfer rate from host material to optical fiber is established to provide an accurate theoretical prediction. On the basis of the theoretical analysis, influence parameters of the middle layers that affect the average strain transfer rate of the six-layer surface-bonded FBG are discussed. After the parametric study, a selection scheme of sensor parameters for numerical validation, which makes the average strain transfer rate approach unity, is determined. Good agreement is observed between numerical results and theoretical predictions. In the end, the six-layer model is extended to the general situation of multiple substrate layers, which lays a theoretical groundwork for the research and design of surface-bonded FBGs with substrate layers in the future. PMID:22722290

  7. Cell and tissue kinetics of the subependymal layer in mouse brain following heavy charged particle irradiation

    SciTech Connect

    Manley, N.B.; Fabrikant, J.I.; Alpen, E.L.

    1988-12-01

    The following studies investigate the cellular response and cell population kinetics of the subependymal layer in the mouse brain exposed to heavy charged particle irradiation. Partial brain irradiation with helium and neon ions was confined to one cortex of the brain. Both the irradiated and the unirradiated contralateral cortex showed similar disturbances of the cell and tissue kinetics in the subependymal layers. The irradiated hemisphere exhibited histological damage, whereas the unirradiated side appeared normal histologically. This study concerns the cell population and cell cycle kinetics of the subependymal layer in the mouse brain, and the effects of charged particle irradiations on this cell population. Quantitative high resolution autoradiography was used to study the kinetic parameters in this cell layer. This study should help in understanding the effects of these high-energy heavy ions on normal mammalian brain tissue. The response of the mammalian brain exposure to charged particle ionizing radiation may be extremely variable. It varies from minimal physiological changes to overt tissue necrosis depending on a number of factors such as: the administered dose, dose-rate, the volume of the irradiated tissue, and the biological end-point being examined.

  8. Direct measurements of ensemble particle and surface interactions on homogeneous and patterned substrates 

    E-print Network

    Wu, Hung-Jen

    2006-08-16

    in colloidal ensembles levitated above macroscopic surfaces. TIRM and VM are well established optical microscopy techniques for measuring normal and lateral colloidal excursions near macroscopic planar surfaces. The interactions between particle-particle...

  9. Chemical-thermal quantitative methodology for carbon speciation in damage layers on building surfaces

    SciTech Connect

    Nadia Ghedini; Cristina Sabbioni; Alessandra Bonazza; Giancarlo Gobbi [National Research Council (CNR), Bologna (Italy). Institute of Atmospheric Sciences and Climate

    2006-02-01

    Carbonaceous particles emitted by combustion processes are the main factors responsible for the blackening of buildings. The identification and evaluation of the carbon species constituting the noncarbonate fraction of total carbon in damage layers, particularly in urban areas, are required in order to investigate atmospheric deposition on building surfaces. Since noncarbonate carbon contains organic and elemental carbon originating from various human activities, its measurement and speciation are crucial to the protection and conservation of monuments and ancient masonry, playing an important role both in the proposal of mitigation strategies and in the definition of conservation treatments. The availability of a correct, accurate, and reproducible analytical method for a complete carbon balance is essential in studying the effects of atmospheric pollutants on the environment, including those affecting cultural heritage. A chemical-thermal methodology was set up, and its sensitivity, accuracy, repeatability, and reproducibility were tested on appropriate standard samples of composition similar to the black crusts on stones and mortars. The results indicate that the technique satisfactorily distinguishes among carbon species, particularly those of anthropogenic origin, allowing a reliable evaluation of their quantities in damage layers. In view of the difficulties encountered in applying the thermo-optical methods adopted for the measurement of carbon filters, the proposed methodology contributes to filling the current gap in suitable and reliable analytical procedures in the field of cultural heritage protection. 24 refs., 1 fig., 4 tabs.

  10. Motion of particles with inertia in a compressible free shear layer

    NASA Technical Reports Server (NTRS)

    Samimy, M.; Lele, S. K.

    1991-01-01

    The effects of the inertia of a particle on its flow-tracking accuracy and particle dispersion are studied using direct numerical simulations of 2D compressible free shear layers in convective Mach number (Mc) range of 0.2 to 0.6. The results show that particle response is well characterized by tau, the ratio of particle response time to the flow time scales (Stokes' number). The slip between particle and fluid imposes a fundamental limit on the accuracy of optical measurements such as LDV and PIV. The error is found to grow like tau up to tau = 1 and taper off at higher tau. For tau = 0.2 the error is about 2 percent. In the flow visualizations based on Mie scattering, particles with tau more than 0.05 are found to grossly misrepresent the flow features. These errors are quantified by calculating the dispersion of particles relative to the fluid. Overall, the effect of compressibility does not seem to be significant on the motion of particles in the range of Mc considered here.

  11. Displacement Field Produced by a Surface Source of Vibrations in a Layered Biological Tissue

    NASA Astrophysics Data System (ADS)

    Timanin, E. M.

    2002-01-01

    Theoretical expressions for the components of the displacement vector in a three-layer halfspace with linked and slipping layers are obtained for the case of setting an oscillatory pressure distributed evenly over a circular area at the layer surface. Numerical calculations of the displacement field in the medium are performed for the values of the parameters simulating a skin-fat layer-muscle-liver biological system. The dependences of the oscillatory displacements within tissues on the dimensions and oscillation frequency of the surface source of vibration are studied, and the possibilities of using such a source for the implementation of the sonoelastography method are discussed.

  12. Microporous structure with layered interstitial surface treatment, and method and apparatus for preparation thereof

    NASA Technical Reports Server (NTRS)

    Koontz, Steven L. (inventor)

    1994-01-01

    A microporous structure with layered interstitial surface treatments, and method and apparatus for preparation thereof is presented. The structure is prepared by sequentially subjecting a uniformly surface-treated structure to atomic oxygen treatment to remove an outer layer of surface treatment to a generally uniform depth, and then surface treating the so exposed layer with another surface treating agent. The atomic oxygen/surface treatment steps may optionally be repeated, each successive time to a lesser depth, to produce a microporous structure having multilayered surface treatments. The apparatus employs at least one side arm from a main atomic oxygen-containing chamber. The side arm has characteristic relaxation times such that a uniform atomic oxygen dose rate is delivered to a specimen positioned transversely in the side arm spaced from the main gas chamber.

  13. Microporous structure with layered interstitial surface treatment, and method and apparatus for preparation thereof

    NASA Technical Reports Server (NTRS)

    Koontz, Steven L. (inventor)

    1992-01-01

    A microporous structure with layered interstitial surface treatments, and the method and apparatus for its preparation are disclosed. The structure is prepared by sequentially subjecting a uniformly surface treated structure to atomic oxygen treatment to remove an outer layer of surface treatment to a generally uniform depth, and then surface treating the so exposed layer with another surface treating agent. The atomic oxygen/surface treatment steps may optionally be repeated, each successive time to a lesser depth, to produce a microporous structure having multilayered surface treatments. The apparatus employs at least one side arm from a main oxygen-containing chamber. The side arm has characteristic relaxation times such that a uniform atomic oxygen dose rate is delivered to a specimen positioned transversely in the side arm spaced from the main gas chamber.

  14. Mass transport of deposited particles by surface-to-surface contact.

    PubMed

    McDonagh, A; Sextro, R G; Byrne, M A

    2012-08-15

    The spread of particle-borne contamination by surface-to-surface contact and its implications for exposures within the indoor environment have been observed - largely qualitatively. The present study was conducted with the aim of quantifying the mass transfer efficiency (TE) of deposited aerosol particles when selected soft and hard surfaces come in contact. The surfaces used were 100% cotton, synthetic fleece, plastic laminate and brass. Contact transfer efficiencies ranging from 2 to 45% were observed; these are very significant numbers in terms of hazardous aerosol transport in the environment. Other observations include an increase in the mass transferred with increased surface roughness. An increase in the applied pressure between the two surfaces in contact leads to a step change in transfer efficiency, so that two pressure regimes can be identified, with a transition pressure between them that depends on surface type. Time of contact appears to have little to no effect on the mass transfer efficiency for the surfaces studied, while contaminant loading has some effect that is not systematic. PMID:22683108

  15. Transient Heat Transfer in a Semitransparent Radiating Layer with Boundary Convection and Surface Reflections

    NASA Technical Reports Server (NTRS)

    Siegel, Robert

    1996-01-01

    Surface convection and refractive index are examined during transient radiative heating or cooling of a grey semitransparent layer with internal absorption, emission and conduction. Each side of the layer is exposed to hot or cold radiative surroundings, while each boundary is heated or cooled by convection. Emission within the layer and internal reflections depend on the layer refractive index. The reflected energy and heat conduction distribute energy across the layer and partially equalize the transient temperature distributions. Solutions are given to demonstrate the effect of radiative heating for layers with various optical thicknesses, the behavior of the layer heated by radiation on one side and convectively cooled on the other, and a layer heated by convection while being cooled by radiation. The numerical method is an implicit finite difference procedure with non-uniform space and time increments. The basic method developed in earlier work is expanded to include external convection and incident radiation.

  16. Aerosol size distribution and refractive index from bistatic lidar angular scattering measurements in the surface layer

    SciTech Connect

    Pandithurai, G.; Devara, P.C.S.; Raj, P.E.; Sharma, S. [Indian Inst. of Tropical Meteorology, Pune (India)] [Indian Inst. of Tropical Meteorology, Pune (India)

    1996-05-01

    The results of an inversion method by iteration for determining the aerosol size distribution and the refractive index of atmospheric aerosols in the surface layer from bistatic lidar angular scattering measurements, followed by a brief description of the experimental and data retrieval techniques are presented. The continuous wave, bistatic Argon ion lidar at the Indian Institute of Tropical Meteorology (IITM), Pune (18{degree}31{prime}N, 73{degree}51{prime}E, 559 m AMSL), India has been used for the measurements. Results of the analysis of 420 samples collected over a 7 years` period indicate mean value of size and refractive indices of 4.0 and 1.6, respectively, with greater fraction of larger particles during premonsoon while smaller particles during post-monsoon months at the lidar site. The retrieved aerosol parameters are compared with those determined from spectroradiometer observations at the same site. The results are found well in agreement with those obtained previously by the authors using the library search method. The above observations of angular distribution of scattered intensity are used with an aerosol model to infer the dominant type of aerosols present in the environment in and around the experimental station.

  17. Surface roughening and unstable neck formation in faceted particles. 2: Mathematical modeling

    SciTech Connect

    Sheldon, B.W.; Rankin, J. (Brown Univ., Providence, RI (United States). Div. of Engineering)

    1999-07-01

    Unstable neck formation between two isolated particles was analyzed by considering the effects of both faceted and rounded (i.e., atomically rough'') surfaces. Mathematical descriptions of both neck growth and rupture are developed here. Calculations conducted with these formulations can explain the neck instability observed by Rankin and Boatner. The analysis and the experimental data suggest that the energy barrier associated with forming a new atomic layer on top of a faceted surface can restrict the shape evolution of a crystalline particle, even at moderately high temperatures. The analysis also indicates that this energy barrier can be overcome when the positive curvature which initially exists at a facet/rough surface boundary reverses as a result of neck growth. This latter effect offers an explanation for neck rupture which is consistent with the experimental results. In addition to providing an explanation for this phenomenon, the analyses presented here also demonstrate that surface phase boundaries and step energy barriers can have a significant effect on microstructure evolution during solid-state sintering.

  18. Shear-induced surface alignment of polymer dispersed liquid crystal microdroplets on the boundary layer

    NASA Technical Reports Server (NTRS)

    Parmar, D. S.; Singh, J. J.

    1993-01-01

    Polymer dispersed liquid crystal thin films have been deposited on a glass substrate, utilizing the processes of polymerization and solvent evaporation induced phase separation. Liquid crystal microdroplets trapped on the upper surface of the thin film respond to the shear stress due to air or gas flow on the surface layer. Response to an applied step shear stress input on the surface layer has been measured by measuring the time response of the transmitted light intensity. Initial results on the measurements of the light transmission as a function of the air flow differential pressure indicate that these systems offer features suitable for boundary layer and gas flow sensors.

  19. Roughness determination of plasma-modified surface layers with atomic force microscopy

    Microsoft Academic Search

    N. Almqvist; M. Rubel; P. Wienhold; S. Fredriksson

    1995-01-01

    Graphite surfaces exposed to the deuterium plasma in the TEXTOR tokamak were characterized in detail by means of scanning probe microscopy, ion beam analysis and colorimetry methods. The aim is to study the composition and structure of thin layer deposits formed on surfaces subjected to the tokamak plasma. The surface roughness was measured and parametrized in terms of fractal dimension

  20. The degradation of EBSD-patterns as a tool to investigate surface crystallized glasses and to identify glassy surface layers.

    PubMed

    Wisniewski, Wolfgang; Völksch, Günter; Rüssel, Christian

    2011-12-01

    Surface crystallized samples of glass-ceramics containing cordierite, rhombohedral BaAl?B?O? and fresnoite were analyzed using electron backscatter diffraction (EBSD). The first two materials were chosen because surface crystallized samples of these materials have previously been shown to contain crystals covered by a very thin layer of glass. In all materials, EBSD pattern degradation occurs if the step size of a scan is chosen to be small. It is shown that the minimum step size enabling an evaluable EBSD-scan increases notably, if the crystals are covered by a thin layer of glass. It is also shown that pattern degradation may be utilized to prove the existence of such a thin glass or otherwise thermally sensitive layer. This provides significant information concerning the nucleation process of glasses also with respect to nucleation theory of glass-ceramics. It is also possible to describe the quantity of crystalline surface covered by the thermally sensitive layer. PMID:22088446

  1. Surface Passivation by Quantum Exclusion Using Multiple Layers

    NASA Technical Reports Server (NTRS)

    Hoenk, Michael E. (Inventor)

    2015-01-01

    A semiconductor device has a multilayer doping to provide improved passivation by quantum exclusion. The multilayer doping includes at least two doped layers fabricated using MBE methods. The dopant sheet densities in the doped layers need not be the same, but in principle can be selected to be the same sheet densities or to be different sheet densities. The electrically active dopant sheet densities are quite high, reaching more than 1.times.10.sup.14 cm.sup.-2, and locally exceeding 10.sup.22 per cubic centimeter. It has been found that silicon detector devices that have two or more such dopant layers exhibit improved resistance to degradation by UV radiation, at least at wavelengths of 193 nm, as compared to conventional silicon p-on-n devices.

  2. Surface Layering at the Mercury-Electrolyte Interface

    NASA Astrophysics Data System (ADS)

    Elsen, A.; Murphy, B. M.; Ocko, B. M.; Tamam, L.; Deutsch, M.; Kuzmenko, I.; Magnussen, O. M.

    2010-03-01

    X-ray reflectometry reveals atomic layering at a liquid-liquid interface—mercury in a 0.01 M NaF solution. The interface width exceeds capillary wave theory predictions and displays an anomalous dependence on the voltage applied across it, displaying a minimum positive of the potential of zero charge. The latter is explained by electrocapillary effects and an additional intrinsic broadening of the interface profile, tentatively assigned to polarization of the conduction electrons due to the electric field of the electrochemical double layer at the interface.

  3. Smectic layer transitions at the surface of an isotropic liquid

    NASA Astrophysics Data System (ADS)

    Somoza, A. M.; Mederos, L.; Sullivan, D. E.

    1994-06-01

    A density-functional theory of the interface between a liquid crystal and a wall predicts a first-order wetting transition by the smectic-A phase when the bulk liquid is isotropic. This is preceded by a prewetting transition away from bulk coexistence. The incomplete and complete wetting regimes are accompanied by a finite and an infinite number of layer transitions, respectively. The layering mechanism shows that the transitions can disappear both very near and far from the isotropic-nematic-smectic-A triple point. These results reconcile findings from previous theories and experiments.

  4. Surface Layering at the Mercury-Electrolyte Interface

    SciTech Connect

    Ocko, B.M.; Elsen, A.; Murphy, B.M.; Tamam, L.; Deutsch, M.; Kuzmenko, I.; Magnussen, O.M.

    2010-03-12

    X-ray reflectometry reveals atomic layering at a liquid-liquid interface--mercury in a 0.01 M NaF solution. The interface width exceeds capillary wave theory predictions and displays an anomalous dependence on the voltage applied across it, displaying a minimum positive of the potential of zero charge. The latter is explained by electrocapillary effects and an additional intrinsic broadening of the interface profile, tentatively assigned to polarization of the conduction electrons due to the electric field of the electrochemical double layer at the interface.

  5. Surface Improvement Technology “Wonder Process Craft (WPC)” by Rapid Impact of Fine Particle

    NASA Astrophysics Data System (ADS)

    Miyasaka, Yoshio

    Based on our sandblast and shot peening technology, we have found that utilizing relatively smaller powder for sandblasting enables the modification or the organizational and mechanical features of the ingredient's surface, defying the conventional thought in this subject manner. The technology mentioned previously can be utilized on various ingredients and machinery parts, and its effect is widely recognized. By blasting titanium particles onto the surface of metals, ceramics, or combined substances utilizing the previously mentioned technology, it is possible to attain a thin film layer of titanium deposit that is effective in catalyzing light. This is PIP (Powder Impact Plating) natural catalyst. In today's world where environmental destruction has become a serious issue, we hope to contribute to the improvement of the environment with our highly efficient catalyst.

  6. Analysis of convection in immiscible liquid layers with novel particle tracking velocimetry

    NASA Technical Reports Server (NTRS)

    Koster, J. N.; Prakash, A.; Campbell, T. A.; Pline, A.

    1992-01-01

    The problem under study is convective flow in immiscible liquid layers with one or two horizontal interfaces. In one-g the flow results primarily from the buoyancy force acting perpendicular to the interfaces. This creates a fluid mechanical system in which the coupling of the fluid layers across an interface plays a fundamental role. The contribution of two horizontal interface tension forces is marginal. Interface tension driven flow requires testing in microgravity. A flight experiment on the Bubble, Drop, and Particle Unit (BDPU) is planned for the second International Microgravity Laboratory (IML-2) mission onboard the Shuttle in 1994. The flow velocity fields will be analyzed by a whole-field Particle Displacement Tracking (PDT) velocimetry technique. The capabilities of this technique to address fundamental issues, such as those regarding the flow stucture, will be discussed with a few sample experiments. Experimental and numerical flow patterns are compared.

  7. Boosting Fano resonances in single layered concentric core-shell particles.

    PubMed

    Sancho-Parramon, Jordi; Jelovina, Denis

    2014-11-21

    Efficient excitation of Fano resonances in plasmonic systems usually requires complex nano-structure geometries and some degree of symmetry breaking. However, a single-layered concentric core-shell particle presents inherent Fano profiles in the scattering spectra when sphere and cavity modes spectrally overlap. Weak hybridization and suitable choice of core and shell materials gives rise to strong electric dipolar Fano resonances in these systems and retardation effects can result in resonances of higher multipolar order or of magnetic type. Furthermore, suitable tailoring of illumination conditions leads to an enhancement of the Fano resonance by quenching of unwanted electromagnetic modes. Overall, it is shown that single layered core-shell particles can act as robust Fano resonators. PMID:25269097

  8. [Texture variation of CC 5052 aluminum alloy slab from surface to center layer by XRD].

    PubMed

    Chen, Ming-Biao; Liu, Wen-Chang; Ma, Xiao-Yi; Li, Jian; Yang, Qing-Xiang; Wang, Shan; Ma, Min; Liu, Chang; Zhao, Y M

    2013-05-01

    For improvement of the processing and gaining uniformity texture structure and performance of direct chill cast CCAA 5052 aluminum alloy band after first hot rolling with different reduction, the material was annealed at 454 degrees C and then cold rolling with different reduction was conducted, the texture at surface, quarter and center layer of the sample was tested and examined by X-ray diffraction method, the data calculated using special software and the difference of texture at surface, quarter and center layer was analyzed. There existed an elevated gradient of intensity from surface layer to center layer after cold rolled with less than or equal to 40% reduction, The main texture of beta is stronger mainly due to transformation from remainder exposure, while the goss and remainder is infirm, the state of texture at each layer is close to each other after cold rolling with reduction high than 56.1%. PMID:23905353

  9. Optical detector having a plurality of matrix layers with cobalt disilicide particles embedded therein

    NASA Technical Reports Server (NTRS)

    Fathauer, Robert W. (inventor); Schowalter, Leo (inventor)

    1994-01-01

    Silicon and metal are coevaporated onto a silicon substrate in a molecular beam epitaxy system with a larger than stoichiometric amount of silicon so as to epitaxially grow particles of metal silicide embedded in a matrix of single crystal epitaxially grown silicon. The particles interact with incident photons by resonant optical absorption at the surface plasmon resonance frequency. Controlling the substrate temperature and deposition rate and time allows the aspect ratio of the particles to be tailored to desired wavelength photons and polarizations. The plasmon energy may decay as excited charge carriers of phonons, either of which can be monitored to indicate the amount of incident radiation at the selected frequency and polarization.

  10. Atomic layer deposition of TiO 2 films on particles in a fluidized bed reactor

    Microsoft Academic Search

    David M. King; Xinhua Liang; Yun Zhou; Casey S. Carney; Luis F. Hakim; Peng Li; Alan W. Weimer

    2008-01-01

    Atomic layer deposition (ALD) of controlled-thickness TiO2 films was carried out on particle substrates in a fluidized bed reactor for the first time. Films were deposited on 550 nm SiO2 spheres and 65 nm ZnO nanoparticles for enhanced optical properties. Nanoparticles were fluidized with the assistance of a magnetically-coupled stirring unit. The metalorganic precursor titanium tetraisopropoxide was used here followed by either

  11. Functionalised nanoscale coatings using layer-by-layer assembly for imparting antibacterial properties to polylactide-co-glycolide surfaces.

    PubMed

    Gentile, Piergiorgio; Frongia, Maria E; Cardellach, Mar; Miller, Cheryl A; Stafford, Graham P; Leggett, Graham J; Hatton, Paul V

    2015-07-15

    In order to achieve high local biological activity and reduce the risk of side effects of antibiotics in the treatment of periodontal and bone infections, a localised and temporally controlled delivery system is desirable. The aim of this research was to develop a functionalised and resorbable surface to contact soft tissues to improve the antibacterial behaviour during the first week after its implantation in the treatment of periodontal and bone infections. Solvent-cast poly(d,l-lactide-co-glycolide acid) (PLGA) films were aminolysed and then modified by Layer-by-Layer technique to obtain a nano-layered coating using poly(sodium4-styrenesulfonate) (PSS) and poly(allylamine hydrochloride) (PAH) as polyelectrolytes. The water-soluble antibiotic, metronidazole (MET), was incorporated from the ninth layer. Infrared spectroscopy showed that the PSS and PAH absorption bands increased with the layer number. The contact angle values had a regular alternate behaviour from the ninth layer. X-ray Photoelectron Spectroscopy evidenced two distinct peaks, N1s and S2p, indicating PAH and PSS had been introduced. Atomic Force Microscopy showed the presence of polyelectrolytes on the surface with a measured roughness about 10nm after 20 layers' deposition. The drug release was monitored by Ultraviolet-visible spectroscopy showing 80% loaded-drug delivery in 14days. Finally, the biocompatibility was evaluated in vitro with L929 mouse fibroblasts and the antibacterial properties were demonstrated successfully against the keystone periodontal bacteria Porphyromonas gingivalis, which has an influence on implant failure, without compromising in vitro biocompatibility. In this study, PLGA was successfully modified to obtain a localised and temporally controlled drug delivery system, demonstrating the potential value of LbL as a coating technology for the manufacture of medical devices with advanced functional properties. PMID:25871538

  12. Two-Layer Variable Infiltration Capacity Land Surface Representation for General Circulation Models

    NASA Technical Reports Server (NTRS)

    Xu, L.

    1994-01-01

    A simple two-layer variable infiltration capacity (VIC-2L) land surface model suitable for incorporation in general circulation models (GCMs) is described. The model consists of a two-layer characterization of the soil within a GCM grid cell, and uses an aerodynamic representation of latent and sensible heat fluxes at the land surface. The effects of GCM spatial subgrid variability of soil moisture and a hydrologically realistic runoff mechanism are represented in the soil layers. The model was tested using long-term hydrologic and climatalogical data for Kings Creek, Kansas to estimate and validate the hydrological parameters. Surface flux data from three First International Satellite Land Surface Climatology Project Field Experiments (FIFE) intensive field compaigns in the summer and fall of 1987 in central Kansas, and from the Anglo-Brazilian Amazonian Climate Observation Study (ABRACOS) in Brazil were used to validate the mode-simulated surface energy fluxes and surface temperature.

  13. Influence of haze layers upon remotely-sensed surface properties

    NASA Technical Reports Server (NTRS)

    Jurica, G. M.; Murray, W. L.

    1972-01-01

    The possibility that the presence of hazy layers contributes to anomalous effects in airplane remote sensing data on corn blight distribution is studied. Computations of scattering angles along flightlines are used to estimate reflected intensity variations as observed in bright and dark sides along flightline of the aircraft.

  14. Method for removing surface-damaged layers from nickel alloys

    NASA Technical Reports Server (NTRS)

    Fawley, R. W.

    1968-01-01

    Electrical discharge machining /EDM/ damaged layer can be effectively removed from Rene 41, Inconel 625, Inconel 718, and Monel K-500 by abrasive-grit blasting or electropolishing /at room temperature/ at a current density of 5A/inches squared in a water solution of phosphoric and sulfuric acids.

  15. Non-extensive treatment of surface nucleation on glass particles

    NASA Astrophysics Data System (ADS)

    Nascimento, Marcio Luis Ferreira

    2012-12-01

    Experimental data of phase transformation kinetics was used to fit a new model based on a non-extensive formalism derived from Tsallis thermostatistics and another based on the Johnson-Mehl-Avrami-Yerofeyev-Kolmogorov (JMAYK) theory. For this we considered the same experimental parameters such as crystal geometric factor g, the density of nucleation sites, NS and crystal growth rates U on glass powders. The kinetics of nucleation and growth of diopside crystals (MgO?CaO?2SiO2) on the glass surface at 825 °C (Tg˜727 °C) were studied. Treatments for sinter-crystallization were performed in compacts of diopside glass particles by varying the treatment time. The crystallized fraction of the samples subjected to such treatments, which develop from the particlessurface toward their volume, was characterized by means of optical microscopy and X-ray diffraction. The two models were then fitted to the measured crystallized fraction data and compared to each other. It was found that surface nucleation occurs very rapidly from a random number of active sites. The JMAYK theory describes the case of fast heterogeneous nucleation from a constant number of sites on the glass surface. The Tsallis approach is better than the JMAYK model considering that the q factor equals 1.268±0.062 and does not require taking into account the change in crystallization mode from three dimensional to one dimensional as JMAYK predicts, and this is advantageous. Furthermore, Tsallis thermostatistics contains the Austin-Rickett model as a special and limiting case study for this system. A generalized Avrami plot is also presented.

  16. Tomographic Particle Image Velocimetry Measurements of a High Reynolds Number Turbulent Boundary Layer

    NASA Astrophysics Data System (ADS)

    Atkinson, Callum; Stanislas, Michel; Soria, Julio

    2009-11-01

    Streamwise/wall-parallel volumes in the buffer region of a turbulent boundary layer at Re? =7800 and 11800 are measured using a 4 camera (2048 x 2048 px) tomographic particle image velocimetry (Tomo-PIV) system in the turbulent boundary layer wind tunnel at the Laboratoire de M'ecanique de Lille (LML). Measurement volumes of 1200 x 180 x 1200 pixels are achieved, the large boundary layer provided by this tunnel (?˜ 0.3 m) resulting in volumes of 470^+ x 70^+ x 470^+ and 920^+ x 140^+ x 920^+ wall units, respectively. The quality of the data acquired by this technique is assessed based on the mean velocity profile, velocity fluctuations, velocity power spectrum and the fluctuating divergence. Streaks and streamwise vortices are examined and an attempt is made to classify the flow using the invariants of the full velocity gradient tensor.

  17. Observations of Turbulence in the Ocean Surface Boundary Layer: Energetics and Transport

    E-print Network

    Gerbi, Gregory P.

    Observations of turbulent kinetic energy (TKE) dynamics in the ocean surface boundary layer are presented here and compared with results from previous observational, numerical, and analytic studies. As in previous studies, ...

  18. Rapid Melt and Resolidification of Surface Layers Using Intense, Pulsed Ion Beams Final Report

    SciTech Connect

    Renk, Timothy J.

    1998-10-02

    The emerging technology of pulsed intense ion beams has been shown to lead to improvements in surface characteristics such as hardness and wear resistance, as well as mechanical smoothing. We report hereon the use of this technology to systematically study improvements to three types of metal alloys - aluminum, iron, and titanium. Ion beam tieatment produces a rapid melt and resolidification (RMR) of the surface layer. In the case of a predeposited thin-fihn layer, the beam mixes this layer into the substrate, Ieading to improvements that can exceed those produced by treatment of the alloy alone, In either case, RMR results in both crystal refinement and metastable state formation in the treated surface layer not accessible by conventional alloy production. Although more characterization is needed, we have begun the process of relating these microstructural changes to the surface improvements we discuss in this report.

  19. Experimental investigation of 3D acoustic receptivity of an airfoil boundary layer due to surface vibrations

    Microsoft Academic Search

    A. V. Ivanov; W. Wurz; S. Herr; S. Wagner; Y. S. Kachanov

    2005-01-01

    The three-dimensional acoustic receptivity of laminar boundary layers in presence of microscopic surface vibrations (the vibro-acoustic receptivity) is examined. The flow under investigation is the boundary layer on an airfoil at relatively high Reynolds numbers close to realistic ones for gliders. This flow has favourable and adverse pressure gradients and develops on a curved wall. The goal of the present

  20. Electronic Properties of Si Surfaces and Side Reactions during Electrochemical Grafting of Phenyl Layers

    E-print Network

    Shapira, Yoram

    Electronic Properties of Si Surfaces and Side Reactions during Electrochemical Grafting of Phenyl donor group is present at the phenyl ring (nitrobenzene) and vice versa for the electron acceptor group/organic layer interfaces, even in the submonolayer regime.4,9-13 A method to graft phenyl layers from

  1. The detection and measurement of turbulent structures in the atmospheric surface layer

    Microsoft Academic Search

    J. L. J. Schols

    1984-01-01

    Turbulence data from the planetary boundary layer (PBL) indicate the presence of deterministic turbulent structures. These structures often show up as asymmetric ramp patterns in measurements of the turbulent fluctuations of a scalar quantity in the atmospheric surface layer (ASL). The sign of the slope of the sharp upstream edge of such a triangular pattern depends on the thermal stability

  2. The Role of Surface and Boundary Layer Dynamics in Arctic Ozone Depletion Episodes

    Microsoft Academic Search

    R. M. Staebler; J. Fuentes; J. W. Bottenheim

    2009-01-01

    Results from the 2009 IPY-OASIS field project in Barrow, AK, will be presented to define the turbulence state of the atmospheric surface layer as well as the structure of the atmospheric boundary layer. There is evidence that vertical mixing in the lower atmosphere frequently, if not always, determines the onset as well as the demise of tropospheric ozone depletion episodes

  3. Snowplow Surface Discharge in Magnetic Field for High Speed Boundary Layer Control

    Microsoft Academic Search

    S. H. Zaidi; T. Smith; S. Macheret; R. B. Miles

    The performance of air breathing supersonic and hypersonic vehicles is strongly affected by the boundary layer that forms along the surface of the inlet. At off- design operating conditions, a shockwave intersecting the boundary layer can cause the flow to separate which may lead to a drastic reduction in vehicle performance. The work presented in this paper explores a possible

  4. Surface roughening and unstable neck formation in faceted particles. 1: Experimental results and mechanisms

    SciTech Connect

    Rankin, J.; Sheldon, B.W. (Brown Univ., Providence, RI (United States). Div. of Engineering)

    1999-07-01

    Experimental in situ TEM results described by Rankin and Boatner are surprising because they show initial neck formation between two isolated MgO particles, followed by neck rupture. A quantitative assessment of the original images shows that initial neck growth corresponds to material removed from the rounded edges which contact the neck, and that neck rupture transfers material directly from the neck to the adjacent faceted faces. During the initial neck growth process surface diffusion along the rounded edges of the crystals is apparently the dominant mass transport mechanism, and material is not transferred to the faceted faces because of the energy barrier associated with forming a new atomic layer on top of a faceted surface. This energy barrier can apparently be overcome when a curvature reversal at a facet/rough surface boundary creates a step which makes it possible to add one or more new atomic layers to the faceted face(s). This can move material away from the neck, and thus lead to neck rupture.

  5. Impact of Atmospheric Surface-layer Parameterizations in the new Land-surface Scheme of the NCEP Mesoscale Eta Model

    Microsoft Academic Search

    Fei Chen; Zavis? Janji?; Kenneth Mitchell

    1997-01-01

    We tested three atmospheric surface-layer parameterization schemes (Mellor-Yamadalevel 2, Paulson, and modified Louis), both ina 1-D mode in the new NCEP land-surface scheme against long-term FIFE and HAPEX observations, and in a coupled 3-D mode withthe NCEP mesoscale Eta model. The differences inthese three schemes and the resulting surface exchange coefficients do not, in general, lead to significant differences in

  6. Build your world and play in it: Interacting with surface particles on complex objects

    Microsoft Academic Search

    Brett R. Jones; Rajinder Sodhi; Roy H. Campbell; Guy Garnett; Brian P. Bailey

    2010-01-01

    We explore interacting with everyday objects by representing content as interactive surface particles. Users can build their own physical world, map virtual content onto their physical construction and play directly with the surface using a stylus. A surface particle representation allows programmed content to be created independent of the display object and to be reused on many surfaces. We demonstrated

  7. Method and system for treating an interior surface of a workpiece using a charged particle beam

    SciTech Connect

    Swenson, David Richard (Georgetown, MA)

    2007-05-23

    A method and system of treating an interior surface on an internal cavity of a workpiece using a charged particle beam. A beam deflector surface of a beam deflector is placed within the internal cavity of the workpiece and is used to redirect the charged particle beam toward the interior surface to treat the interior surface.

  8. Interaction of bacterial surface layer proteins with lipid membranes: synergysm between surface charge density and chain packing.

    PubMed

    Hollmann, Axel; Delfederico, Lucrecia; De Antoni, Graciela; Semorile, Liliana; Disalvo, Edgardo Aníbal

    2010-08-01

    S-layer proteins from Lactobacillus kefir and Lactobacillus brevis are able to adsorb on the surface of positively charged liposomes composed by Soybean lecithin, cholesterol and stearylamine. The different K values for S-layer proteins isolated from L. kefir and L. brevis (4.22 x 10(-3) and 2.45 x 10(2) microM(-1) respectively) indicates that the affinity of the glycosylated protein isolated from L. kefir is higher than the non-glycosylated one. The attachment of S-layer proteins counteracts the electrostatic charge repulsion between stearylamine molecules in the membrane surface, producing an increase in the rigidity in the acyl chains as measured by DPH anisotropy. Laurdan generalized polarization (GP) shows that glycosylated causes a GP increase, attributed to a lowering in water penetration into the head groups of membrane phospholipids, with charge density reduction, while the non-glycosylated does not affect it. The octadecyl-rhodamine results indicate that S-layer coated liposomes do not show spontaneous dequenching in comparison with control liposomes without S-layer proteins, suggesting that S-layer protein avoid spontaneous liposomal fusion. It is concluded that the increase in stability of liposomes coated with S-layers proteins is due to the higher rigidity induced by the S-layer attachment by electrostatic forces. PMID:20417069

  9. Near Surface Vapor Bubble Layers in Buoyant Low Stretch Burning of Polymethylmethacrylate

    NASA Technical Reports Server (NTRS)

    Olson, Sandra L.; Tien, J. S.

    1999-01-01

    Large-scale buoyant low stretch stagnation point diffusion flames over solid fuel (polymethylmethacrylate) were studied for a range of aerodynamic stretch rates of 2-12/ sec which are of the same order as spacecraft ventilation-induced stretch in a microgravity environment. An extensive layer of polymer material above the glass transition temperature is observed. Unique phenomena associated with this extensive glass layer included substantial swelling of the burning surface, in-depth bubble formation, and migration and/or elongation of the bubbles normal to the hot surface. The bubble layer acted to insulate the polymer surface by reducing the effective conductivity of the solid. The reduced in-depth conduction stabilized the flame for longer than expected from theory neglecting the bubble layer. While buoyancy acts to move the bubbles deeper into the molten polymer, thermocapillary forces and surface regression both act to bring the bubbles to the burning surface. Bubble layers may thus be very important in low gravity (low stretch) burning of materials. As bubbles reached the burning surface, monomer fuel vapors jetted from the surface, enhancing burning by entraining ambient air flow. Popping of these bubbles at the surface can expel burning droplets of the molten material, which may increase the fire propagation hazards at low stretch rates.

  10. Structural properties of particle deposits at heterogeneous surfaces

    NASA Astrophysics Data System (ADS)

    Stojiljkovi?, D.; Š?epanovi?, J. R.; Vrhovac, S. B.; Švraki?, N. M.

    2015-06-01

    The random sequential adsorption (RSA) approach is used to analyze adsorption of spherical particles of a fixed radius on nonuniform flat surfaces covered by rectangular cells. The configuration of the cells (heterogeneities) was produced by performing RSA simulations to a prescribed coverage fraction ?_0{(cell)} . Adsorption was assumed to occur if the particle (projected) center lies within a rectangular cell area, i.e. if sphere touches the cells. The jammed-state properties of the model were studied for different values of cell size ? (comparable with the adsorbing particle size) and density ?_0{(cell)} . Numerical simulations were carried out to investigate adsorption kinetics, jamming coverage, and structure of coverings. Structural properties of the jammed-state coverings were analyzed in terms of the radial distribution function g(r) and distribution of the Delaunay ‘free’ volumes P(v). It was demonstrated that adsorption kinetics and the jamming coverage decreased significantly, at a fixed density ?_0{(cell)} , when the cell size ? increased. The predictions following from our calculation suggest that the porosity (pore volumes) of deposited monolayer can be controlled by the size and shape of landing cells, and by anisotropy of the cell deposition procedure.

  11. Free vibration of functionally graded material beams with surface-bonded piezoelectric layers in thermal environment

    Microsoft Academic Search

    Shi-rong Li; Hou-de Su; Chang-jun Cheng

    2009-01-01

    Free vibration of statically thermal postbuckled functionally graded material (FGM) beams with surface-bonded piezoelectric\\u000a layers subject to both temperature rise and voltage is studied. By accurately considering the axial extension and based on\\u000a the Euler-Bernoulli beam theory, geometrically nonlinear dynamic governing equations for FGM beams with surface-bonded piezoelectric\\u000a layers subject to thermo-electromechanical loadings are formulated. It is assumed that the

  12. Numerical modeling of the development of a preferentially leached layer on feldspar surfaces

    Microsoft Academic Search

    Changbing Yang; Javier Samper; Chen Zhu; Scott B. Jones

    2009-01-01

    Compositional depth profiles in the leached layer of feldspar surfaces are usually interpreted by using analytical solutions\\u000a which introduce oversimplifying assumptions. Here we present a general multicomponent interdiffusion numerical model for simulating\\u000a cation release from a preferentially leached layer on feldspar surfaces in acid solutions. The numerical model takes into\\u000a account interdiffusion, dissolution of the solid phase (represented by a

  13. On the coupling between a supersonic boundary layer and a flexible surface

    NASA Technical Reports Server (NTRS)

    Frendi, Abdelkader; Maestrello, Lucio; Bayliss, Alvin

    1992-01-01

    The coupling between a two-dimensional, supersonic, laminar boundary layer and a flexible surface is studied using direct numerical computations of the Navier-Stokes equations coupled with the plate equation. The flexible surface is forced to vibrate by plane acoustic waves at normal incidence emanated by a sound source located on the side of the flexible surface opposite to the boundary layer. The effect of the source excitation frequency on the surface vibration and boundary layer stability is analyzed. We find that, for frequencies near the fifth natural frequency of the surface or lower, large disturbances are introduced in the boundary layer which may alter its stability characteristics. The interaction between a stable two-dimensional disturbance of Tollmien-Schlichting (TS) type with the vibrating surface is also studied. We find that the disturbance level is higher over the vrating flexible surface than that obtained when the surface is rig id, which indicates a strong coupling between flow and structure. However, in the absence of the sound source the disturbance level over the rigid and flexible surfaces are identical. This result is due to the high frequency of the TS disturbance which does not couple with the flexible surface.

  14. Observations of the sensitivity of beam attenuation to particle size in a coastal bottom boundary layer

    NASA Astrophysics Data System (ADS)

    Hill, P. S.; Boss, E.; Newgard, J. P.; Law, B. A.; Milligan, T. G.

    2011-02-01

    The goal of this study was to test the hypothesis that the aggregated state of natural marine particles constrains the sensitivity of optical beam attenuation to particle size. An instrumented bottom tripod was deployed at the 12-m node of the Martha's Vineyard Coastal Observatory to monitor particle size distributions, particle size-versus-settling-velocity relationships, and the beam attenuation coefficient (cp) in the bottom boundary layer in September 2007. An automated in situ filtration system on the tripod collected 24 direct estimates of suspended particulate mass (SPM) during each of five deployments. On a sampling interval of 5 min, data from a Sequoia Scientific LISST 100x Type B were merged with data from a digital floc camera to generate suspended particle volume size distributions spanning diameters from approximately 2 ?m to 4 cm. Diameter-dependent densities were calculated from size-versus-settling-velocity data, allowing conversion of the volume size distributions to mass distributions, which were used to estimate SPM every 5 min. Estimated SPM and measured cp from the LISST 100x were linearly correlated throughout the experiment, despite wide variations in particle size. The slope of the line, which is the ratio of cp to SPM, was 0.22 g m-2. Individual estimates of cp:SPM were between 0.2 and 0.4 g m-2 for volumetric median particle diameters ranging from 10 to 150 ?m. The wide range of values in cp:SPM in the literature likely results from three factors capable of producing factor-of-two variability in the ratio: particle size, particle composition, and the finite acceptance angle of commercial beam-transmissometers.

  15. A simple stochastic quadrant model for the transport and deposition of particles in turbulent boundary layers

    NASA Astrophysics Data System (ADS)

    Jin, C.; Potts, I.; Reeks, M. W.

    2015-05-01

    We present a simple stochastic quadrant model for calculating the transport and deposition of heavy particles in a fully developed turbulent boundary layer based on the statistics of wall-normal fluid velocity fluctuations obtained from a fully developed channel flow. Individual particles are tracked through the boundary layer via their interactions with a succession of random eddies found in each of the quadrants of the fluid Reynolds shear stress domain in a homogeneous Markov chain process. In this way, we are able to account directly for the influence of ejection and sweeping events as others have done but without resorting to the use of adjustable parameters. Deposition rate predictions for a wide range of heavy particles predicted by the model compare well with benchmark experimental measurements. In addition, deposition rates are compared with those obtained from continuous random walk models and Langevin equation based ejection and sweep models which noticeably give significantly lower deposition rates. Various statistics related to the particle near wall behavior are also presented. Finally, we consider the model limitations in using the model to calculate deposition in more complex flows where the near wall turbulence may be significantly different.

  16. Origin and consequences of silicate glass passivation by surface layers

    NASA Astrophysics Data System (ADS)

    Gin, Stéphane; Jollivet, Patrick; Fournier, Maxime; Angeli, Frédéric; Frugier, Pierre; Charpentier, Thibault

    2015-02-01

    Silicate glasses are durable materials, but are they sufficiently durable to confine highly radioactive wastes for hundreds of thousands years? Addressing this question requires a thorough understanding of the mechanisms underpinning aqueous corrosion of these materials. Here we show that in silica-saturated solution, a model glass of nuclear interest corrodes but at a rate that dramatically drops as a passivating layer forms. Water ingress into the glass, leading to the congruent release of mobile elements (B, Na and Ca), is followed by in situ repolymerization of the silicate network. This material is at equilibrium with pore and bulk solutions, and acts as a molecular sieve with a cutoff below 1?nm. The low corrosion rate resulting from the formation of this stable passivating layer enables the objective of durability to be met, while progress in the fundamental understanding of corrosion unlocks the potential for optimizing the design of nuclear glass-geological disposal.

  17. Origin and consequences of silicate glass passivation by surface layers

    PubMed Central

    Gin, Stéphane; Jollivet, Patrick; Fournier, Maxime; Angeli, Frédéric; Frugier, Pierre; Charpentier, Thibault

    2015-01-01

    Silicate glasses are durable materials, but are they sufficiently durable to confine highly radioactive wastes for hundreds of thousands years? Addressing this question requires a thorough understanding of the mechanisms underpinning aqueous corrosion of these materials. Here we show that in silica-saturated solution, a model glass of nuclear interest corrodes but at a rate that dramatically drops as a passivating layer forms. Water ingress into the glass, leading to the congruent release of mobile elements (B, Na and Ca), is followed by in situ repolymerization of the silicate network. This material is at equilibrium with pore and bulk solutions, and acts as a molecular sieve with a cutoff below 1?nm. The low corrosion rate resulting from the formation of this stable passivating layer enables the objective of durability to be met, while progress in the fundamental understanding of corrosion unlocks the potential for optimizing the design of nuclear glass-geological disposal. PMID:25695377

  18. Origin and consequences of silicate glass passivation by surface layers.

    PubMed

    Gin, Stéphane; Jollivet, Patrick; Fournier, Maxime; Angeli, Frédéric; Frugier, Pierre; Charpentier, Thibault

    2015-01-01

    Silicate glasses are durable materials, but are they sufficiently durable to confine highly radioactive wastes for hundreds of thousands years? Addressing this question requires a thorough understanding of the mechanisms underpinning aqueous corrosion of these materials. Here we show that in silica-saturated solution, a model glass of nuclear interest corrodes but at a rate that dramatically drops as a passivating layer forms. Water ingress into the glass, leading to the congruent release of mobile elements (B, Na and Ca), is followed by in situ repolymerization of the silicate network. This material is at equilibrium with pore and bulk solutions, and acts as a molecular sieve with a cutoff below 1?nm. The low corrosion rate resulting from the formation of this stable passivating layer enables the objective of durability to be met, while progress in the fundamental understanding of corrosion unlocks the potential for optimizing the design of nuclear glass-geological disposal. PMID:25695377

  19. Formation of nanocrystalline layers by surface severe plastic deformation and pulsed plasma electrolytic carburizing.

    PubMed

    Aliofkhazraei, M; Rouhaghdam, A Sabour

    2010-07-01

    Surfaces of various kinds of metallic materials spheres were treated by nanocrystalline surface severe plastic deformation and then pulsed nanocrystalline plasma electrolytic carburizing to study nanocrystalline substrate effect on formation and nano-hardness of hard nanocrystalline layer. The surface layers of the metallic materials developed by the nanocrystalline surface severe plastic deformation were characterized by means of high resolution scanning electron microscope. Nearly equiaxed nanocrystals with grain sizes ranging from 15 to 90 nm were observed in the near surface regions of all metallic materials, which are low carbon steel and commercially pure titanium. The effect of substrate nanocrystallization on growth kinetics and hardness of formed nanocrystalline carbide layer was studied with the means of figure analysis and nanohardness tests. Figure analysis show the length to diameter ratio and distribution curve of nanocrystals and it has been found that the achieved properties of hard layer (growth rate, nano-hardness, nanostructure...) are related to these factors. It was also clarified that these techniques and surface nanocrystallization can be easily achieved in most of metallic materials. Results indicate that the resultant hardened carburized layers exhibited excellent hardness profile. Investigation of the layer characteristics showed strong dependence followed from the treatment experimental parameters as well as the shape of nanocrystals. PMID:21128498

  20. Bistatic scattering from three-dimensional layered rough surfaces

    Microsoft Academic Search

    Alireza Tabatabaeenejad; Mahta Moghaddam

    2006-01-01

    An analytical method to calculate the bistatic-scattering coefficients of a three-dimensional layered dielectric structure with slightly rough interfaces is presented. The interfaces are allowed to be statistically distinct, but possibly dependent. The waves in each region are represented as a superposition of an infinite number of up- and down-going spectral components whose amplitudes are found by simultaneously matching the boundary

  1. Simultaneous detection of separation and transition in surface shear layers

    Microsoft Academic Search

    Siva M. Mangalam; J. P. Stack; W. G. Sewall

    1989-01-01

    Flush-mounted hot-film gages have proved effective in detecting boundary-layer transition and in measuring skin friction but with limited success in detecting laminar separation and reattachment. The development of multielement micro hot-film sensors, and the recent discovery of the phase reversal phenomena associated with low-frequency dynamic shear stress signals across regions of laminar separation and turbulent reattachment, have made it possible

  2. Toughening of layered ceramic composites with residual surface compression

    Microsoft Academic Search

    R. Lakshminarayanan; D. K. Shetty; Raymond A. Cutler

    1996-01-01

    Effects of macroscopic residual stresses on fracture toughness of multilayered ceramic laminates were studied analytically and experimentally. Stress intensities for edge cracks in three-layer, single-edge-notch-bend (SENB) specimens with stepwise varying residual stresses in the absence of the crack and superimposed bending were calculated as a function of the crack length by the method of weight function. The selected weight function

  3. Synthesis of superhydrophobic SiO{sub 2} layers via combination of surface roughness and fluorination

    SciTech Connect

    Kim, Eun-Kyeong; Yeong Kim, Ji [School of Materials Science and Engineering, Inha University, Incheon 402-751 (Korea, Republic of); Sub Kim, Sang, E-mail: sangsub@inha.ac.kr [School of Materials Science and Engineering, Inha University, Incheon 402-751 (Korea, Republic of)

    2013-01-15

    We describe the preparation of superhydrophobic SiO{sub 2} layers through a combination of surface roughness and fluorination. Electrospraying SiO{sub 2} precursor solutions that were prepared by a sol-gel route and included trichloro(1H,1H,2H,2H-perfluorooctyl)silane as a fluorination source produced highly rough, fluorinated SiO{sub 2} layers. In sharp contrast to the fluorinated flat SiO{sub 2} layer, the fluorinated rough SiO{sub 2} layer showed much enhanced repellency toward liquid droplets of different surface tensions. The surface fraction and the work of adhesion of the superhydrophobic SiO{sub 2} layers were determined, respectively, based on Cassie-Baxter and Young-Dupre equations. The satisfactory long-term stability for 30 days, the ultraviolet resistance and the thermal stability up to 400 {sup o}C of the superhydrophobic SiO{sub 2} layers prepared in this work confirm a promising practical application. - Graphical abstract: A schematic illustration of the electrospray deposition used for preparing SiO{sub 2} layers. Shapes of liquid droplets of water, glycerol, coffee, juice and milk created on the fluorinated rough SiO{sub 2} layer deposited on a silicon wafer. Highlights: Black-Right-Pointing-Pointer Superhydrophobic SiO{sub 2} layers are realized by a combination of surface roughness and fluorination. Black-Right-Pointing-Pointer The fluorinated rough SiO{sub 2} layer shows enhanced repellency toward various liquid droplets. Black-Right-Pointing-Pointer The wetting behavior is explained based on Cassie-Baxter and Young-Dupre equations. Black-Right-Pointing-Pointer The superhydrophobic SiO{sub 2} layers confirm a promising practical application.

  4. Particle image velocimetry for the surface tension driven convection experiment using a particle displacement tracking technique

    NASA Technical Reports Server (NTRS)

    Wernet, Mark P.; Pline, Alexander D.

    1991-01-01

    The Surface Tension Driven Convection Experiment (STDCE) is a Space Transportation System flight experiment to study both transient and steady thermocapillary fluid flows aboard the USML-1 Spacelab mission planned for 1992. One of the components of data collected during the experiment is a video record of the flow field. This qualitative data is then quantified using an all electronic, two-dimensional particle image velocimetry technique called particle displacement tracking (PDT) which uses a simple space domain particle tracking algorithm. The PDT system is successful in producing velocity vector fields from the raw video data. Application of the PDT technique to a sample data set yielded 1606 vectors in 30 seconds of processing time. A bottom viewing optical arrangement is used to image the illuminated plane, which causes keystone distortion in the final recorded image. A coordinate transformation was incorporated into the system software to correct this viewing angle distortion. PDT processing produced 1.8 percent false identifications, due to random particle locations. A highly successful routine for removing the false identifications was also incorporated, reducing the number of false identifications to 0.2 percent.

  5. Loading and release of fluorescent dye from layer-by-layer film-coated magnetic particles in response to hydrogen peroxide.

    PubMed

    Sato, Katsuhiko; Abe, Eiichi; Takahashi, Mao; Anzai, Jun-ichi

    2014-10-15

    Polymer-coated magnetic particles (MPs) were prepared to study the binding of fluorescence dye on the surface and its H2O2-induced release. For this goal, multilayer films were prepared by layer-by-layer deposition of shikimic acid-appended poly(allylamine hydrochloride) (SA-PAH) and poly(styrenesulfonate) (PSS) on the surface of MPs. 3-(Dansylamino)phenylboronic acid (DPBA) was loaded on the MPs through boronate ester bonding between SA-PAH and DPBA. DPBA was released from the MPs in response to H2O2 as a result of breakage of the boronate ester bond by an oxidative reaction with H2O2. DPBA release was dependent on the H2O2 concentration. For example, 65% and 93% of the DPBA was released from (SA-PAH/PSS)4SA-PAH film-coated MPs in 30min after the addition of 0.1 and 0.5mM H2O2, respectively. In addition, the multilayer film-coated MPs were further modified by using glucose oxidase (GOx) to develop glucose-induced release systems. GOx-modified MPs released DPBA in response to 0.1mM d-glucose as a result of H2O2 generation through a GOx-catalyzed oxidation reaction of d-glucose. The results suggest a potential use of the multilayer film-coated MPs in the development of H2O2- and/or glucose-sensitive drug delivery systems. PMID:25084230

  6. Damage to polymer-coated glass surfaces by small-particle impact

    NASA Astrophysics Data System (ADS)

    Chaudhri, Mohammad M.; Smith, Alan L.

    1991-04-01

    A high speed photographic investigation of the impact damage processes of soda-lime glass surfaces coated with thin layers of a self adhesive tape and polyurethane rubber has been described. The impacting particles were 1-mm steel spheres and had velocities in the range of 50-250 ms1. The photography was performed at a framing rate of 1 million per second. It is shown that, depending upon the impact velocities, the coatings debonded and perforated by the impact and therefore they provided very little protection to the coated surface. The coatings also tended to adhere to the projectile and during its rebound this caused tensile stresses normal to the impacted surface. Additional tensile stresses during the projectile rebound were caused by the rapid contraction of the piled up coating. These stresses are probably responsible for the enhanced growth of the lateral cracks in the coated glass surfaces. The coatings, however, reduced the amount of jetting' of the fragmented material and the removal of the surface chips developed during unloading.

  7. Bidirectional Reflectance of Flat, Optically Thick Particulate Layers: An Efficient Radiative Transfer Solution and Applications to Snow and Soil Surfaces

    NASA Technical Reports Server (NTRS)

    Mishchenko, Michael I.; Dlugach, Janna M.; Yanovitsku, Edgard G.; Zakharova, Nadia T.

    1999-01-01

    We describe a simple and highly efficient and accurate radiative transfer technique for computing bidirectional reflectance of a macroscopically flat scattering layer composed of nonabsorbing or weakly absorbing, arbitrarily shaped, randomly oriented and randomly distributed particles. The layer is assumed to be homogeneous and optically semi-infinite, and the bidirectional reflection function (BRF) is found by a simple iterative solution of the Ambartsumian's nonlinear integral equation. As an exact Solution of the radiative transfer equation, the reflection function thus obtained fully obeys the fundamental physical laws of energy conservation and reciprocity. Since this technique bypasses the computation of the internal radiation field, it is by far the fastest numerical approach available and can be used as an ideal input for Monte Carlo procedures calculating BRFs of scattering layers with macroscopically rough surfaces. Although the effects of packing density and coherent backscattering are currently neglected, they can also be incorporated. The FORTRAN implementation of the technique is available on the World Wide Web at http://ww,,v.giss.nasa.gov/-crmim/brf.html and can be applied to a wide range of remote sensing, engineering, and biophysical problems. We also examine the potential effect of ice crystal shape on the bidirectional reflectance of flat snow surfaces and the applicability of the Henyey-Greenstein phase function and the 6-Eddington approximation in calculations for soil surfaces.

  8. Estimation of Surface Heat Fluxes at Field Scale Using Surface Layer Versus Mixed-Layer Atmospheric Variables with Radiometric Temperature Observations.

    NASA Astrophysics Data System (ADS)

    Kustas, William P.; Prueger, John H.; Humes, Karen S.; Starks, Patrick J.

    1999-02-01

    Radiometric surface temperature observations TR(), near-surface meteorological/surface energy flux (METFLUX), and atmospheric boundary layer (ABL) data were collected during the Washita '94 Experiment conducted in the Little Washita Experimental Watershed near Chickasha, Oklahoma. The TR() measurements were made from ground and aircraft platforms near the METFLUX stations located over vegetated surfaces of varying amounts of cover and over bare soil. Continuous, half-hourly averaged ground-based TR() measurements essentially at the point scale were calibrated with periodic ground transect and aircraft-based TR() observations at coarser resolutions so that the continuous TR() measurements would be representative of surface temperatures at the field scale (i.e., on the order of 104 m2). The METFLUX data were collected nominally at 2 m above the surface, while ABL measurements were made in the lower 8-10 km of the atmosphere. The `local' wind speed, u, and air temperature, TA, from the METFLUX stations, as well as the mixed-layer wind speed, UM, and potential temperature, M, were used in a two-source energy balance model for computing fluxes with continuous TR() measurements from the various surfaces. Standard Monin-Obukhov surface layer similarity was used with the `local' u and TA data from the METFLUX stations. Bulk similarity approaches were used with the UM and M data referenced either to ABL height or the top of the surface layer. This latter approach of using mixed-layer data to drive model computations for the different sites is similar to the so-called flux-aggregation schemes or methods proposed to account for subgrid variability in atmospheric models, such as the`tile' or `mosaic' approach. There was less agreement between modeled and measured fluxes when using mixed-layer versus local meteorological variables data for driving the model, and the type of bulk formulation used (i.e., whether local or regional surface roughness was used) also had a significant impact on the results. Differences between the flux observations and model predictions using surface layer similarity with local u and TA data were about 25% on average, while using the bulk formulations with UM and M differences averaged about 30%. This larger difference was caused by an increase in biases and scatter between modeled and measured fluxes for some sites. Therefore, computing spatially distributed local-scale fluxes with ABL observations of mixed-layer properties will probably yield less reliable flux predictions than using local meteorological data, if available. Given the uncertainty in flux observations is about 20%, these estimates are still considered reasonable and moreover permit the mapping of spatially distributed surface fluxes at regional scales using a single observation of UM and M with high resolution TR() data. Such TR() observations with a 90-m pixel resolution will be available from the Advanced Spaceborne Thermal Emission and Reflection Radiometer to be launched on NASA's Earth Observing System.

  9. EMF measurements across the front of combustion wave during layer by layer surface laser sintering of exothermal powder compositions

    NASA Astrophysics Data System (ADS)

    Shishkovskiy, I.; Sherbakov, V.; Morozov, Yu.

    2007-06-01

    Rapid prototyping (RP) and manufacturing (M) is a novel layer-by-layer fabrication technique which has become increasingly popular due to its inherent flexibility for the manufacture of simple and complex 3D parts. Early we had been shown opportunity of selective laser sintering (SLS) of different type powder systems (intermetallics, ceramics, ferrites, high-temperature superconductors), traditional use for self-propagated high-temperature synthesis (SHS). The non-thermal heating affect of an external electromagnetic field during SHS is related to the specific system under study due to differences in movement of defects and ions at the 'plasma-like' molten combustion wave front. We have developed and refined the testing scheme for electro-thermal phenomena studies which can directly influence on the SHS combustion wave front. This work studies electromotive force (EMF) measurements across the front of combustion wave during layer by layer surface laser sintering of exothermal powder compositions (Ni-Ti, Ni-Al). Analysis using an analog-digital-analog computer converter allowed some control of the laser movement and hence some control of the exothermal reaction - in so doing it provided near optimum conditions for forming layered 3D articles. Comparative results of structural-phase transformation during laser control SHS in reaction-capable compositions are presented.

  10. Surface passivation of InP solar cells with InAlAs layers

    NASA Technical Reports Server (NTRS)

    Jain, Raj K.; Flood, Dennis J.; Landis, Geoffrey A.

    1993-01-01

    The efficiency of indium phosphide solar cells is limited by high values of surface recombination. The effect of a lattice-matched In(0.52)Al(0.48)As window layer material for InP solar cells, using the numerical code PC-1D is investigated. It was found that the use of InAlAs layer significantly enhances the p(+)n cell efficiency, while no appreciable improvement is seen for n(+)p cells. The conduction band energy discontinuity at the heterojunction helps in improving the surface recombination. An optimally designed InP cell efficiency improves from 15.4 percent to 23 percent AMO for a 10 nm thick InAlAs layer. The efficiency improvement reduces with increase in InAlAs layer thickness, due to light absorption in the window layer.

  11. Surface modification of poly(propylene carbonate) by aminolysis and layer-by-layer assembly for enhanced cytocompatibility.

    PubMed

    Zhong, Xia; Lu, Zufu; Valtchev, Peter; Wei, Hua; Zreiqat, Hala; Dehghani, Fariba

    2012-05-01

    Poly(propylene carbonate) (PPC) is a biodegradable polymer with desirable mechanical properties for bone and cartilage repair. However, the poor biocompatibility impedes its applications in tissue engineering. The aim of this study was to evaluate the effect of surface modification of PPC on the improvement of its cytocompatibility. The combination of aminolysis and layer-by-layer (LBL) assembly techniques was used to modify the PPC surface. The results of ATR-FTIR measurement demonstrated that PPC was aminolyzed by polyethylenimine (PEI) at specific reaction conditions and the degree of aminolyzation was quantitatively determined by ninhydrin method. Positively charged PEI and negatively charged gelatin were alternatively deposited on the aminolyzed PPC membranes at pH 7.4, which formed polyelectrolyte multilayers surface with gelatin as the outermost layer. The presence of amino groups on the aminolyzed PPC and gelatin on the multilayers had significant impact on enhancing the hydrophilicity of PPC. Fibroblast and primary human osteoblasts (HOBs) were used to assess the cytocompatibility of PPC. The deposition of PEI and gelatin bilayers on PPC remarkably promoted both fibroblast and HOBs cell attachment, spreading and growth. In particular, the osteogenic gene expression of HOBs cultured on the multilayers modified PPC was substantially increased. The aminolysis followed by LBL assembly is a convenient and cost effective technique for enhancing cell attachment and proliferation. The product has high potential for musculoskeletal tissue engineering applications due to its desirable mechanical strength and tunable cytocompatibility. PMID:22244300

  12. Scale properties of microscale convection in the marine surface layer

    SciTech Connect

    Hagelberg, C.R.; Cooper, D.I.; Winter, C.L. [Los Alamos National Laboratory, Los Alamos, New Mexico (United States)] [Los Alamos National Laboratory, Los Alamos, New Mexico (United States); Eichinger, W.E. [Department of Civil and Environmental Engineering, University of Iowa, Iowa City (United States)] [Department of Civil and Environmental Engineering, University of Iowa, Iowa City (United States)

    1998-07-01

    We analyze the scale distribution of coherent water vapor structures in the marine atmospheric boundary layer as measured by a shipboard Raman lidar during the Combined Sensor Program (March 1996) using a two-dimensional continuous wavelet transform. Coherent structures in the lidar measured water vapor concentration field correspond to locations where covariance with the wavelet is a local extremum. Scales of the significant structures are identified using a filtered wavelet variance (detection density) derived from 24 {open_quotes}images{close_quotes} in a horizontal plane. A dominant radius of 14 m is identified using complimentary approaches to the analysis. {copyright} 1998 American Geophysical Union

  13. An experimental study of surface curvature effects on a supersonic turbulent boundary layer

    NASA Technical Reports Server (NTRS)

    Chou, J. H.; Childs, M. E.

    1983-01-01

    The mean flow results of an experimental study of compressible turbulent boundary layers in an adverse pressure gradient with and without surface curvature effects are presented. The test was conducted in an axisymmetric flow facility. The upstream Reynolds number based on boundary layer momentum thickness was 5884 and the boundary layer thickness was 0.90 cm. The curvature effects were examined by studying two flows with essentially identical adverse pressure gradients. One flow was along a concave compression surface test section, while the other was along a straight-walled test section. Mean flow measurements included wall static pressure distributions, wall temperatures, pitot pressure profiles and total temperature profiles. The mean flow results indicated that the surface curvature resulted in a definite increase of turbulent mixing in the boundary layer.

  14. Measurement and correlation of aerodynamic heating to surface corrugation stiffened structures in thick turbulent boundary layers

    NASA Technical Reports Server (NTRS)

    Brandon, H. J.; Masek, R. V.

    1974-01-01

    The flow conditions for which heating distributions were measured on corrugated surfaces and wavy walls in turbulent boundary layers are shown, along with the ratio of the displacement thickness to the roughness height versus the local edge Mach number for an equivalent smooth surface. The present data are seen to greatly extend the range of data available on corrugated surfaces in turbulent boundary layers. These data were obtained by testing fullscale corrugation roughened panels in the wall boundary layer of a supersonic and hypersonic wind tunnel. The experimental program used to obtain the data is described. The data are analyzed and correlated in terms of the pertinent flow and geometric parameters. The developed correlations are compared with the available thin boundary layer data, as well as with previously published correlation techniques.

  15. Interactions between volume and surface EM waves in layered structures

    NASA Technical Reports Server (NTRS)

    Ushioda, S.

    1984-01-01

    Using light scattering spectroscopy, the interaction of Surface Plasmon Polariton SPP in silver films on a glass substrate is with the incident radiation and with optical phonons of an external medium in contact with the film. The mean free path and the field strength of SPP are determined. The same SPP plays an important role in light emitting tunnel junctions (LETJ) in which an electrical current is converted into Volume Electromagnetic Wave VEW. The efficiency of light emission from LETJ through a prism coupler rather than through surface roughness is discussed. The coupling between phonon surface polaritons (PhSP) and optical guided waves (OGW) in thin films of GaP is also examined.

  16. CHARACTERIZING SURFACE LAYERS IN NITINOL USING X-RAY PHOTOELECTRON SPECTROSCOPY

    SciTech Connect

    Christopfel, R.; Mehta, A.

    2008-01-01

    Nitinol is a shape memory alloy whose properties allow for large reversible deformations and a return to its original geometry. This nickel-titanium (NiTi) alloy has become a material used widely in the biomedical fi eld as a stent to open up collapsed arteries. Both ambient and biological conditions cause surface oxidation in these devices which in turn change its biocompatibility. The thickness of oxidized layers can cause fractures in the material if too large and can allow for penetration if too thin. Depending on the type and abundance of the chemical species on or near the surface, highly toxic metal ions can leak into the body causing cell damage or even cell death. Thus, biocompatibility of such devices is crucial. By using highly surface sensitive x-ray photoelectron spectroscopy to probe the surface of these structures, it is possible to decipher both layer composition and layer thickness. Two samples, both of which were mechanically polished, were investigated. Of the two samples, one was then exposed to a phosphate buffered saline (PBS) solution to mimic the chemical properties of blood, while the other remained unexposed. Although both samples were found to have oxide layers of appropriate thickness (on the order of a few nm), it was found that the sample exposed to the saline solution had a slightly thicker oxide layer and more signifi cantly, a phosphate layer very near the surface suggesting toxic metal components are well contained within the sample. These are considerable indications of a biocompatible device.

  17. Impact of Boundary-Layer Processes on Near-Surface Turbulence Within the West African Monsoon

    NASA Astrophysics Data System (ADS)

    Lohou, Fabienne; Saïd, Frédérique; Lothon, Marie; Durand, Pierre; Serça, Dominique

    2010-07-01

    High frequency measurements of near-surface meteorological data acquired in north Benin during the 2006 West African monsoon seasonal cycle, in the context of the African Monsoon Multidisciplinary Analysis (AMMA) experiment, offer insight into the characteristics of surface turbulence in relation to planetary boundary-layer (PBL) processes. A wide range of conditions is encountered at the lower and upper limits of the PBL: (i) from water-stressed to well-fed vegetation, and (ii) from small to large humidity and temperature jumps at the PBL top inversion, due to the Saharan air layer overlying the monsoonal flow. As a result, buoyant convection at the surface and entrainment at the PBL top play very different roles according to the considered scalar. We show that, when the boundary-layer height reaches the shear level between the monsoonal and Harmattan flows, the temperature source and humidity sink at the boundary-layer top are sufficient to allow the entrainment to affect the entire boundary layer down to the surface. This situation occurs mainly during the drying and moistening periods of the monsoon cycle and affects the humidity statistics in particular. In this case, the humidity turbulent characteristics at the surface are no longer driven solely by buoyant convection, but also by entrainment at the boundary-layer top. Consequently, the Monin-Obukhov similarity theory appears to fail for the parameterisation of humidity-related moments.

  18. Packet Structure of Surface Eddies in the Atmospheric Boundary Layer

    NASA Astrophysics Data System (ADS)

    Hommema, Scott E.; Adrian, Ronald J.

    A smoke visualization experiment has beenperformed in the first 3,m ofneutral and unstable atmospheric boundary layersat very large Reynolds number(Re > 106). Under neutral atmosphericconditions mean wind profiles agreewell with those in the canonical flatplate zero-pressure-gradient turbulentboundary layer. The experiment was designedto minimize the temperaturedifference between the passive marker (smoke)and the air to ensure that anyobserved structures were due to vortical, ratherthan buoyant, motions. Imagesacquired in the streamwise-wall-normal planeusing a planar laser light-sheetare strikingly similar to those observed inlaboratory experiments at low to moderate Reynolds numbers. They reveal large-scaleramp-like structures withdownstream inclination of 3°-35°.This inclination isinterpreted as the hairpin packet growthangle following the hairpin vortexpacket model ofAdrian, Meinhart, and Tomkins.The distribution of this characteristicangle agrees with the results of experiments at far lower Reynolds numbers,suggesting a similarity in structures among low, moderate, and high Reynoldsnumber boundary layers at vastly different scales. These results indicate thatthe hairpin vortex packet model extends over a large range of scales. Theeffect of vertical heat transport in an unstable atmosphere on wall structuresis investigated in terms of the hairpin vortex packet model.

  19. Anisotropic layer-by-layer growth of graphene on vicinal SiC(0001) surfaces

    Microsoft Academic Search

    Satoru Tanaka; Kouhei Morita; Hiroki Hibino

    2010-01-01

    Epitaxial graphene is formed on vicinal SiC(0001) surfaces via high temperature annealing in vacuum. Steps act as a significant ``kicker'' of graphene nucleation to feed C atoms. At elevated temperatures, graphene growth is controlled by the decomposition of Si-C bonds at step edges, Si desorption, and C diffusion on the surface. The limited Si desorption is due to the dependence

  20. Stability Criteria for the Boundary Layer Formed by Through ow at a Horizontal Surface of a Porous Medium

    E-print Network

    Eindhoven, Technische Universiteit

    ]). As the surface is relatively cold, a ther- mal boundary layer of cool water is formed below the surface through ow induced by evaporation, the salt re- mains behind at the surface to form saline deposits (saltStability Criteria for the Boundary Layer Formed by Through ow at a Horizontal Surface of a Porous

  1. Surface Passivation of Silicon Solar Cells using Amorphous Silicon Carbide Layers

    Microsoft Academic Search

    S. W. Glunz; S. Janz; M. Hofmann; T. Roth; G. Willeke

    2006-01-01

    Dielectric layers for the passivation of solar cell surfaces are a crucial component of future cell generations. Not only their electrical and optical properties are of importance but also the implementation into an industrial cell process. In this regard an easy preconditioning of the surface, low process temperature and high thermal stability are essential. Therefore, we have developed a new

  2. Forensic Investigation to Determine the Reasons for Premature Failure in an Asphalt Surface Layer

    Microsoft Academic Search

    Emile Horak; Stephen J. Emery

    2010-01-01

    Premature failure in the form of cracking, stripping and brittleness of a hot mix asphalt surfacing on a major road in South Africa was investigated. Anecdotal evidence as well as pavement structural evaluation with the FWD confirmed that the distress was restricted to the surface layer alone. Testing on the recovered binder indicated that excessive filler material was present in

  3. Immobilization of Nucleic Acids at Solid Surfaces: Effect of Oligonucleotide Length on Layer Assembly

    Microsoft Academic Search

    A. B. Steel; R. L. Levicky; T. M. Herne; M. J. Tarlov

    2000-01-01

    This report investigates the effect of DNA length and the presence of an anchoring group on the assembly of presynthesized oligonucleotides at a gold surface. The work seeks to advance fundamental insight into issues that impact the structure and behavior of surface-immobilized DNA layers, as in, for instance, DNA microarray and biosensor devices. The present study contrasts immobilization of single-stranded

  4. Large eddy simulation of separated flows from a surface mounted obstacle in turbulent boundary layers

    Microsoft Academic Search

    Kojiro Nozawa; Tetsuro Tamura

    2001-01-01

    Numerical investigations have been performed for the flow past a surface mounted obstacle in turbulent boundary layers using LES. It is well known that the separated flow is strongly affected by oncoming turbulence, which result in not only the deformation of the mean flow profile but also the onset of negative peak pressure, which occurs intermittently on the surface of

  5. OFFLINE EVALUATION OF SIX SURFACE LAYER PARAMETERIZATION SCHEMES AGAINST OBSERVATIONS AT THE ARM SGP SITE

    E-print Network

    OFFLINE EVALUATION OF SIX SURFACE LAYER PARAMETERIZATION SCHEMES AGAINST OBSERVATIONS AT THE ARM of surface fluxes collected by the DOE (Department of Energy) ARM (Atmospheric Radiation Measurement) program to quantify the uncertainty/discrepancy between the ARM measurements based on the EC (Eddy Correlation

  6. Wind-Tunnel Study Of Atmospheric Stable Boundary Layers Over A Rough Surface

    Microsoft Academic Search

    Yuji Ohya

    2001-01-01

    Wind-tunnel simulations of theatmospheric stable boundary layer (SBL) developedover a rough surface were conducted by using athermally stratified wind tunnel at the Research Institutefor Applied Mechanics (RIAM), Kyushu University. Thepresent experiment is a continuation of the workcarried out in a wind tunnel at Colorado StateUniversity (CSU), where the SBL flows were developed over asmooth surface. Stably stratified flows were createdby

  7. A model of evaporative cooling of wet skin surface and fur layer

    Microsoft Academic Search

    Kifle G. Gebremedhin; Binxin Wu

    2001-01-01

    (1) A theoretical model that simultaneously solves heat and mass transfer in a wet skin surface and fur layer that occurs when an animal is cooled by blowing air over its wetted skin surface and hair coat is presented. (2) The model predicts evaporative and convective heat losses for different levels of wetness, air velocity, ambient temperature, relative humidity and

  8. Measuring air layer volumes retained by submerged floating-ferns Salvinia and biomimetic superhydrophobic surfaces

    PubMed Central

    Reker, Meike; Barthlott, Wilhelm

    2014-01-01

    Summary Some plants and animals feature superhydrophobic surfaces capable of retaining a layer of air when submerged under water. Long-term air retaining surfaces (Salvinia-effect) are of high interest for biomimetic applications like drag reduction in ship coatings of up to 30%. Here we present a novel method for measuring air volumes and air loss under water. We recorded the buoyancy force of the air layer on leaf surfaces of four different Salvinia species and on one biomimetic surface using a highly sensitive custom made strain gauge force transducer setup. The volume of air held by a surface was quantified by comparing the buoyancy force of the specimen with and then without an air layer. Air volumes retained by the Salvinia-surfaces ranged between 0.15 and 1 L/m2 depending on differences in surface architecture. We verified the precision of the method by comparing the measured air volumes with theoretical volume calculations and could find a good agreement between both values. In this context we present techniques to calculate air volumes on surfaces with complex microstructures. The introduced method also allows to measure decrease or increase of air layers with high accuracy in real-time to understand dynamic processes. PMID:24991518

  9. A High Resolution Study of the Effect of Morphology on the Mass Spectra of Single PSL Particles with Na-Containing Layers and Nodules

    SciTech Connect

    Cai, Yong; Zelenyuk, Alla; Imre, Dan G.

    2006-12-29

    The interpretation and qualification of measurements of particle composition by laser ablation based single particle mass spectroscopy is complex. Among the most difficult system to quantify are internally mixed particles containing alkali metals. The Alkali atoms in such particles tend to suppress the formation of other ions sometimes to below detection limit. Here we present a study of the behavior of the single particle mass spectral peak intensities as a function of the amount of the sodium containing compounds deposited on the surface of 240 nm PSL spheres. We generate three morphologically distinct and well defined coating types: uniform layer, cubic nodules and rounded nodules, and measure the individual particle mass spectra as a function of the vacuum aerodynamic diameter with nanometer resolution. We find that the probability of detecting the PSL spheres depends on the amount of the alkali metal on the PSL sphere surface and the ablation laser power. We also find that the morphological distribution of the sodium containing coating plays a role in determining mass spectral intensities. The data suggest that PSL spheres with localized Na-containing nodules are easier to detect than those completely encapsulated. We show that 80% of PSL spheres with nodules, whose weight fraction is close to 50%, can be detected at high laser power compared with 60% detection of encapsulated PSL particles with the same amount of coating. At low laser powers these detection limits drop to 35% and ~0% respectively.

  10. Particle-hole asymmetry in gapped topological insulator surface states

    NASA Astrophysics Data System (ADS)

    Tabert, C. J.; Carbotte, J. P.

    2015-06-01

    We consider the combined effect of a gap and the Zeeman interaction on the helical Dirac fermions that exist on the surface of a topological insulator. Magneto-optical properties, the magnetization, Hall effect, and the density of states are considered with emphasis on the particle-hole asymmetry, which arises when a subdominant Schrödinger piece is included along with the dominant Dirac part of the Hamiltonian. When appropriate, we compare our results with those of a single-valley gapped graphene system for which Zeeman splitting behaves differently. We provide a derivation of the phase offset in the magnetic oscillations brought about by the combined effect of the gap and Schrödinger term without requiring the semiclassical Onsager quantization condition. Our results agree with previous discussions based on semiclassical arguments.

  11. Low loss Sendust powder cores comprised of particles coated by sodium salt insulating layer

    NASA Astrophysics Data System (ADS)

    Wei, Ding; Wang, Xian; Nie, Yan; Feng, Zekun; Gong, Rongzhou; Chen, Yajie; Harris, V. G.

    2015-05-01

    Toroid-shaped Sendust powder cores were prepared from cold pressing mechanically pulverized Fe-Si-Al powder that had been coated using an inorganic insulating layer. The present work focuses on the effect of the sodium salt-coated Sendust particles upon the high frequency magnetic properties. Sendust powders, having a particle size range of ˜125 ?m, exhibit a high saturation magnetization of 118.9 A.m2/kg and a low coercivity of 56 A/m. The experiments indicate that the sodium-based glass insulating layer synthesized from sodium metaphosphate and sodium metaborate can effectively reduce the change in permeability with frequency or DC bias field, yielding high effective permeability (?e) of ˜113 over a wide frequency range from 10 kHz-1 MHz. Furthermore, the effective permeability is measured at ˜27 at H = 7854 A/m, indicating stable and high effective permeability under a DC bias field. The measurements of permeability under DC bias field indicate a peak in the quality factor (Q) values corresponding to a DC-bias field of 1.5-6 (kA/m) at frequencies from 50 to 200 kHz: The effective permeability remains at ˜74. The sodium salt-coated granular cores demonstrate a core loss of 68 mW/cm3 at Bm = 50 mT and f = 50 kHz: These values compare favorably to those of silicone coated Sendust particles.

  12. One-dimensional particle simulations of Knudsen-layer effects on D-T fusion

    NASA Astrophysics Data System (ADS)

    Cohen, Bruce I.; Dimits, Andris M.; Zimmerman, George B.; Wilks, Scott C.

    2014-12-01

    Particle simulations are used to solve the fully nonlinear, collisional kinetic equation describing the interaction of a high-temperature, high-density, deuterium-tritium plasma with absorbing boundaries, a plasma source, and the influence of kinetic effects on fusion reaction rates. Both hydrodynamic and kinetic effects influence the end losses, and the simulations show departures of the ion velocity distributions from Maxwellian due to the reduction of the population of the highest energy ions (Knudsen-layer effects). The particle simulations show that the interplay between sources, plasma dynamics, and end losses results in temperature anisotropy, plasma cooling, and concomitant reductions in the fusion reaction rates. However, for the model problems and parameters considered, particle simulations show that Knudsen-layer modifications do not significantly affect the velocity distribution function for velocities most important in determining the fusion reaction rates, i.e., the thermal fusion reaction rates using the local densities and bulk temperatures give good estimates of the kinetic fusion reaction rates.

  13. Leonid's Particle Analyses from Stratospheric Balloon Collection on Xerogel Surfaces

    NASA Technical Reports Server (NTRS)

    Noever, David; Phillips, Tony; Horack, John; Porter, Linda; Myszka, Ed

    1999-01-01

    Recovered from a stratospheric balloon above 20 km on 17-18 November 1998, at least eight candidate microparticles were collected and analyzed from low-density silica xerogel collection plates. Capture time at Leonids' storm peak was validated locally along the balloon trajectory by direct video imaging of meteor fluence up to 24/hr above 98% of the Earth's atmosphere. At least one 30 micron particle agrees morphologically to a smooth, unmelted spherule and compares most closely in non-volatile elemental ratios (Mg/Si, Al/Si, and Fe/Si) to compositional data in surface/ocean meteorite collections. A Euclidean tree diagram based on composition makes a most probable identification as a non-porous stratospherically collected particle and a least probable identification as terrestrial matter or an ordinary chondrite. If of extraterrestrial origin, the mineralogical class would be consistent with a stony (S) type of silicate, olivine [(Mg,Fe)2SiO4] and pyroxene [(Mg, Fe)Si!O3)--or oxides, herecynite [(Fe,Mg) Al2O4].

  14. High-speed particle image velocimetry near surfaces.

    PubMed

    Lu, Louise; Sick, Volker

    2013-01-01

    Multi-dimensional and transient flows play a key role in many areas of science, engineering, and health sciences but are often not well understood. The complex nature of these flows may be studied using particle image velocimetry (PIV), a laser-based imaging technique for optically accessible flows. Though many forms of PIV exist that extend the technique beyond the original planar two-component velocity measurement capabilities, the basic PIV system consists of a light source (laser), a camera, tracer particles, and analysis algorithms. The imaging and recording parameters, the light source, and the algorithms are adjusted to optimize the recording for the flow of interest and obtain valid velocity data. Common PIV investigations measure two-component velocities in a plane at a few frames per second. However, recent developments in instrumentation have facilitated high-frame rate (>1 kHz) measurements capable of resolving transient flows with high temporal resolution. Therefore, high-frame rate measurements have enabled investigations on the evolution of the structure and dynamics of highly transient flows. These investigations play a critical role in understanding the fundamental physics of complex flows. A detailed description for performing high-resolution, high-speed planar PIV to study a transient flow near the surface of a flat plate is presented here. Details for adjusting the parameter constraints such as image and recording properties, the laser sheet properties, and processing algorithms to adapt PIV for any flow of interest are included. PMID:23851899

  15. Controllable surface haptics via particle jamming and pneumatics.

    PubMed

    Stanley, Andrew A; Okamura, Allison M

    2015-01-01

    The combination of particle jamming and pneumatics allows the simultaneous control of shape and mechanical properties in a tactile display. A hollow silicone membrane is molded into an array of thin cells, each filled with coffee grounds such that adjusting the vacuum level in any individual cell rapidly switches it between flexible and rigid states. The array clamps over a pressure-regulated air chamber with internal mechanisms designed to pin the nodes between cells at any given height. Various sequences of cell vacuuming, node pinning, and chamber pressurization allow the surface to balloon into a variety of shapes. Experiments were performed to expand existing physical models of jamming at the inter-particle level to define the rheological characteristics of jammed systems from a macroscopic perspective, relevant to force-displacement interactions that would be experienced by human users. Force-displacement data show that a jammed cell in compression fits a Maxwell model and a cell deflected in the center while supported only at the edges fits a Zener model, each with stiffness and damping parameters that increase at higher levels of applied vacuum. This provides framework to tune and control the mechanical properties of a jamming haptic interface. PMID:25594980

  16. Low-temperature nitriding of 38CrMoAl steel with a nanostructured surface layer induced by surface mechanical attrition treatment

    Microsoft Academic Search

    W. P. Tong; Z. Han; L. M. Wang; J. Luc; K. Lua

    2008-01-01

    A nanocrystalline surface layer was fabricated on a 38CrMoAl steel plate by means of a surface mechanical attrition treatment (SMAT). The average grain size in the top surface layer (10 ?m thick) is about 10 nm, and the grain size stability can be maintained up to 450 °C. The effect of the surface nanocrystalline layer on the gas nitriding process at a lower

  17. Displacement interaction and surface curvature effects on hypersonic boundary layers.

    NASA Technical Reports Server (NTRS)

    Wornom, S. F.; Werle, M. J.

    1972-01-01

    The title problem was studied employing implicit finite-difference methods to obtain numerical solutions to a composite set of boundary-layer equations valid to second order. Results are given for flow up a two-dimensional cubic compression ramp for free-stream Mach numbers of 6, 8, and 12.25 and for free-stream Re/inch equal to 85,800 and 25,800 at a wall-to-stagnation temperature ratio of 0.223. Comparisons with independent theories and experimental results are given. Nonsingular separation was produced at a free-stream Mach number of 12.25. For all cases considered, displacement and curvature effects canceled one another when a consistent treatment of inviscid and viscous curvature corrections was employed - the second-order theory virtually reproducing the first-order results.

  18. Modification on surface oxide layer structure and surface morphology of niobium by gas cluster ion beam treatments

    SciTech Connect

    A. T. Wu, D. R. Swenson, Z. Insepov

    2010-09-01

    Recently, it was demonstrated that significant reductions in field emission on Nb surfaces could be achieved by means of a new surface treatment technique called gas cluster ion beam (GCIB). Further study as shown in this paper revealed that GCIB treatments could modify surface irregularities and remove surface asperities leading to a smoother surface finish as demonstrated through measurements using a 3D profilometer, an atomic force microscope, and a scanning electron microscope. These experimental observations were supported by computer simulation via atomistic molecular dynamics and a phenomenological surface dynamics. Measurements employing a secondary ion mass spectrometry found that GCIB could also alter Nb surface oxide layer structure. Possible implications of the experimental results on the performance of Nb superconducting radio frequency cavities treated by GCIB will be discussed. First experimental results on Nb single cell superconducting radio frequency cavities treated by GCIB will be reported.

  19. Insight in layer-by-layer assembly of cysteamine and L-cysteine on the copper surface by electrochemistry and Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Song, Ping; Shen, Shu; Li, Chuan-Chuan; Guo, Xiao-Yu; Wen, Ying; Yang, Hai-Feng

    2015-02-01

    In this work, we examined the relationship between the anticorrosion behavior and the structure of the cysteamine/L-cysteine layer-by-layer coating on the copper surface via the self-assembled monolayers (SAMs) technique with electrochemistry and surface-enhanced Raman scattering (SERS) spectroscopy. SERS results elucidated the layer-by-layer adsorption mechanism of cysteamine/L-cysteine at the copper surface. Electrochemical investigations explored the inhibition behavior of cysteamine/L-cysteine for copper from corrosion with a high protection efficiency of 91.4%.

  20. Comparison of ambient particle surface area measurement by epiphaniometer and SMPS\\/APS

    Microsoft Academic Search

    Ji Ping Shi; Roy M Harrison; Douglas Evans

    2001-01-01

    During measurement campaigns at an urban background and a rural site, simultaneous measurements of particle size distributions using a scanning mobility particle sizer (SMPS)\\/aerodynamic particle sizer (APS) combination and Fuchs surface using an epiphaniometer have been made. The epiphaniometer was calibrated using sub-100nm monodisperse aerosol and it was found that a calibration based upon particle electrical mobility diameters measured with

  1. Convection and correlation of coherent structure in turbulent boundary layer using tomographic particle image velocimetry

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Guan, Xin-Lei; Jiang, Nan

    2014-10-01

    The present experimental work focuses on a new model for space—time correlation and the scale-dependencies of convection velocity and sweep velocity in turbulent boundary layer over a flat wall. A turbulent boundary layer flow at Re? = 2460 is measured by tomographic particle image velocimetry (tomographic PIV). It is demonstrated that arch, cane, and hairpin vortices are dominant in the logarithmic layer. Hairpins and hairpin packets are responsible for the elongated low-momentum zones observed in the instantaneous flow field. The conditionally-averaged coherent structures systemically illustrate the key roles of hairpin vortice in the turbulence dynamic events, such as ejection and sweep events and energy transport. The space—time correlations of instantaneous streamwise fluctuation velocity are calculated and confirm the new elliptic model for the space—time correlation instead of Taylor hypothesis. The convection velocities derived from the space—time correlation and conditionally-averaged method both suggest the scaling with the local mean velocity in the logarithmic layer. Convection velocity result based on Fourier decomposition (FD) shows stronger scale- dependency in the spanwise direction than in streamwise direction. Compared with FD, the proper orthogonal decomposition (POD) has a distinct distribution of convection velocity for the large- and small-scales which are separated in light of their contributions of turbulent kinetic energy.

  2. Solution-processed amorphous silicon surface passivation layers

    SciTech Connect

    Mews, Mathias, E-mail: mathias.mews@helmholtz-berlin.de; Sontheimer, Tobias; Korte, Lars; Rech, Bernd [Helmholtz-Zentrum Berlin, Institute of Silicon Photovoltaics, Kekuléstraße 5, D-12489 Berlin (Germany); Mader, Christoph; Traut, Stephan; Wunnicke, Odo [Evonik Industries AG, Creavis Technologies and Innovation, Paul-Baumann-Straße 1, D-45772 Marl (Germany)

    2014-09-22

    Amorphous silicon thin films, fabricated by thermal conversion of neopentasilane, were used to passivate crystalline silicon surfaces. The conversion is investigated using X-ray and constant-final-state-yield photoelectron spectroscopy, and minority charge carrier lifetime spectroscopy. Liquid processed amorphous silicon exhibits high Urbach energies from 90 to 120?meV and 200?meV lower optical band gaps than material prepared by plasma enhanced chemical vapor deposition. Applying a hydrogen plasma treatment, a minority charge carrier lifetime of 1.37?ms at an injection level of 10{sup 15}/cm{sup 3} enabling an implied open circuit voltage of 724?mV was achieved, demonstrating excellent silicon surface passivation.

  3. IMPACT OF BOUNDARY-LAYER CUTTING ON FREE-SURFACE

    E-print Network

    California at San Diego, University of

    (FS) Open area ratio 37.1% 0.33 mm dia. wires w/open cell width of 0.51 mm (mesh size 30 × 30.7 cm ID) to rectangular cross-section 10 cm × 3 cm (y × z) · Perforated plate (PP) Open area ratio 50 area of liquid surface · Efficiency factor correlation (valid for Wed = 235­270,000) L mass flux

  4. The North Polar Layered Terrain on Mars: A Very Young Surface

    NASA Astrophysics Data System (ADS)

    Herkenhoff, K. E.; Nowicki, S. A.; Plaut, J. J.

    1996-03-01

    THE NORTH POLAR LAYERED TERRAIN ON MARS: A VERY YOUNG SURFACE; K. E. Herkenhoff1, S. A. Nowicki2, and J. J. Plaut1, 1Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109-8099, 2Augustana College, Rock Island, IL 61201-2296. The Martian polar layered deposits are probably the best source of information about the recent climate history of Mars, but their origin and the mechanisms of accumulation are still a mystery. The polar layers are sedimentary deposits that most planetary scientists believe are composed of water ice and varying amounts of wind-blown dust, but their composition is poorly constrained. Interpretation of the observed polar stratigraphy in terms of global climate changes is complicated by the significant difference in surface ages between the north and south polar layered terrains inferred from crater statistics. While no craters have been found in the north polar layered terrain, the surface of the south polar layered deposits appears to have been stable for many of the orbital/axial cycles that are thought to have induced global climate changes on Mars. Further studies of the polar layered deposits should ultimately lead to a better understanding of the climate history of Mars.

  5. Electronic absorption band broadening and surface roughening of phthalocyanine double layers by saturated solvent vapor treatment

    SciTech Connect

    Kim, Jinhyun [Department of Chemistry, Kookmin University, Seoul 136-702 (Korea, Republic of)] [Department of Chemistry, Kookmin University, Seoul 136-702 (Korea, Republic of); Yim, Sanggyu, E-mail: sgyim@kookmin.ac.kr [Department of Chemistry, Kookmin University, Seoul 136-702 (Korea, Republic of)] [Department of Chemistry, Kookmin University, Seoul 136-702 (Korea, Republic of)

    2012-10-15

    Variations in the electronic absorption (EA) and surface morphology of three types of phthalocyanine (Pc) thin film systems, i.e. copper phthalocyanine (CuPc) single layer, zinc phthalocyanine (ZnPc) single layer, and ZnPc on CuPc (CuPc/ZnPc) double layer film, treated with saturated acetone vapor were investigated. For the treated CuPc single layer film, the surface roughness slightly increased and bundles of nanorods were formed, while the EA varied little. In contrast, for the ZnPc single layer film, the relatively high solubility of ZnPc led to a considerable shift in the absorption bands as well as a large increase in the surface roughness and formation of long and wide nano-beams, indicating a part of the ZnPc molecules dissolved in acetone, which altered their molecular stacking. For the CuPc/ZnPc film, the saturated acetone vapor treatment resulted in morphological changes in mainly the upper ZnPc layer due to the significantly low solubility of the underlying CuPc layer. The treatment also broadened the EA band, which involved a combination of unchanged CuPc and changed ZnPc absorption.

  6. Prediction of Particle Deposition onto Indoor Surfaces by CFD with a Modified Lagrangian Method

    E-print Network

    Chen, Qingyan "Yan"

    surfaces. This study used a 2 -v f turbulence model with a modified Lagrangian method to predict of particle deposition onto indoor surfaces by CFD with a modified Lagrangian method," Atmospheric Environment- 1 - Prediction of Particle Deposition onto Indoor Surfaces by CFD with a Modified Lagrangian

  7. Properties of Semiconductor Surface Inversion Layers in the Electric Quantum Limit

    Microsoft Academic Search

    Frank Stern; W. E. Howard

    1967-01-01

    The strong surface electric field associated with a semiconductor inversion layer quantizes the motion normal to the surface. The bulk energy bands split into electric sub-bands near the surface, each of which is a two-dimensional continuum associated with one of the quantized levels. We treat the electric quantum limit, in which only the lowest electric sub-band is occupied. Within the

  8. A critical study of the role of the surface oxide layer in titanium bonding

    NASA Technical Reports Server (NTRS)

    Dias, S.; Wightman, J. P.

    1982-01-01

    The molecular understanding of the role which the surface oxide layer of the adherend plays in titanium bonding is studied. The effects of Ti6-4 adherends pretreatment, bonding conditions, and thermal aging of the lap shear specimens were studied. The use of the SEM/EDAX and ESCA techniques to study surface morphology and surface composition was emphasized. In addition, contact angles and both infrared and visible reflection spectroscopy were used in ancillary studies.

  9. Controlled surface functionality of magnetic nanoparticles by layer-by-layer assembled nano-films.

    PubMed

    Choi, Daheui; Son, Boram; Park, Tai Hyun; Hong, Jinkee

    2015-04-21

    Over the past several years, the preparation of functionalized nanoparticles has been aggressively pursued in order to develop desired structures, compositions, and structural order. Among the various nanoparticles, iron oxide magnetic nanoparticles (MNPs) have shown great promise because the material generated using these MNPs can be used in a variety of biomedical applications and possible bioactive functionalities. In this study, we report the development of various functionalized MNPs (F-MNPs) generated using the layer-by-layer (LbL) self-assembly method. To provide broad functional opportunities, we fabricated F-MNP bio-toolbox by using three different materials: synthetic polymers, natural polymers, and carbon materials. Each of these F-MNPs displays distinct properties, such as enhanced thickness or unique morphologies. In an effort to explore their biomedical applications, we generated basic fibroblast growth factor (bFGF)-loaded F-MNPs. The bFGF-loaded F-MNPs exhibited different release mechanisms and loading amounts, depending on the film material and composition order. Moreover, bFGF-loaded F-MNPs displayed higher biocompatibility and possessed superior proliferation properties than the bare MNPs and pure bFGF, respectively. We conclude that by simply optimizing the building materials and the nanoparticle's film composition, MNPs exhibiting various bioactive properties can be generated. PMID:25798789

  10. Laser-induced oxidation of titanium substrate: Analysis of the physicochemical structure of the surface and sub-surface layers

    NASA Astrophysics Data System (ADS)

    Anto?czak, Arkadiusz J.; Skowro?ski, ?ukasz; Trzcinski, Marek; Kinzhybalo, Vasyl V.; ?azarek, ?ukasz K.; Abramski, Krzysztof M.

    2015-01-01

    This paper presents the results of the analysis of the complex chemical structure of the layers made on titanium in the process of the heating of its surfaces in an atmospheric environment, by irradiating samples with a nanosecond-pulsed laser. The study was carried out for electroplated, high purity, polycrystalline titanium substrates using a Yb:glass fiber laser. All measurements were made for samples irradiated in a broad range of accumulated fluence, below the ablation threshold. It has been determined how the complex index of refraction of both the oxynitride layers and the substrate vary as a function of accumulated laser fluence. It was also shown that the top layer of the film produced on titanium, which is transparent, is not a pure TiO2 as had been supposed before. The XPS and XRD analyses confirmed the presence of nitrogen compounds and the existence of nonstoichiometric compounds. By sputtering of the sample's surface using an Ar+ ion gun, the changes in the concentration of individual elements as a function of the layer's cross-section were determined. Lastly, an analysis of the surface morphology has also been carried out, explaining why the layers crack and exfoliate from their substrate.

  11. Monte Carlo simulations of light scattering by composite particles in a planetary surface

    NASA Technical Reports Server (NTRS)

    Hillier, J.; Buratti, B.

    2001-01-01

    Composite particles containing internal scatterers have been proposed as an explanation for the fact that most photometric studies of planetary surfaces based on Hapke's bidirectional reflectance model have found the planetary particles to exhibit moderately backscattering phase functions.

  12. Analysis of plasma particle and energy fluxes to material surfaces from tokamak edge turbulence simulations

    NASA Astrophysics Data System (ADS)

    Umansky, M. V.; Cohen, B. I.; Rognlien, T. D.; Boedo, J. A.; Rudakov, D. L.

    2012-10-01

    Recent BOUT simulations of edge plasma turbulence in L-mode regime in the boundary region of DIII-D tokamak have demonstrated reasonable match with key edge diagnostics [1]. Order-of-magnitude level agreement has been found in the characteristic amplitude, wavenumber, and frequency of turbulent fluctuations, as compared with experimental data from reciprocating edge Langmuir probe and Beam Emission Spectroscopy systems. Owing to this encouraging agreement, output data from these simulations are analyzed to get insights on physical mechanisms and properties of plasma particle and energy fluxes to material surfaces. Of particular interest is plasma turbulence propagating into, or generated in, the far scrape-off layer region where plasma interacts with material walls. Results of statistical analyses of simulated turbulence plasma transport will be presented and physical implications will be discussed. [4pt] [1] B.I. Cohen et al., APS-DPP 2012

  13. Polyvalent surface modification of hydrocarbon polymers via covalent layer-by-layer self-assembly

    E-print Network

    Liao, Kang-Shyang

    2009-05-15

    , reversible, reproducible wettability changes can be prepared by covalent LbL grafting using PNIPAM-c-PNASI and aminated silica nanoparticles. A 65º ?? value was observed with water vs. 1.4 M Na2SO4. The prepared film shows a high surface roughness of ~300 nm...

  14. Quasi-medium energy ion scattering spectroscopy observation of surface segregation of Ge ?-doped layer during Si molecular beam epitaxy

    Microsoft Academic Search

    Takashi Fuse; Kiyoshi Kawamoto; Shigenori Kujime; Takashi Shiizaki; Mitsuhiro Katayama; Kenjiro Oura

    1997-01-01

    We have observed the behavior of Ge ?-doped layers fabricated by molecular beam epitaxy (MBE) on an Si(001) substrate and the surface segregation of Ge atoms from ?-doped layers during a top Si buffer layer growth using quasi-medium energy ion scattering spectroscopy. We have found that the Ge atoms segregate to the surface even at a low substrate temperature of

  15. Vector solution for the mean electromagnetic fields in a layer of random particles

    NASA Technical Reports Server (NTRS)

    Lang, R. H.; Seker, S. S.; Levine, D. M.

    1986-01-01

    The mean electromagnetic fields are found in a layer of randomly oriented particles lying over a half space. A matrix-dyadic formulation of Maxwell's equations is employed in conjunction with the Foldy-Lax approximation to obtain equations for the mean fields. A two variable perturbation procedure, valid in the limit of small fractional volume, is then used to derive uncoupled equations for the slowly varying amplitudes of the mean wave. These equations are solved to obtain explicit expressions for the mean electromagnetic fields in the slab region in the general case of arbitrarily oriented particles and arbitrary polarization of the incident radiation. Numerical examples are given for the application to remote sensing of vegetation.

  16. Structural characterization study of nickel ferrite particles dispersed in a corrosion product deposit layer

    NASA Astrophysics Data System (ADS)

    Kuri, G.; Degueldre, C.; Bertsch, J.; Borca, C. N.

    2010-12-01

    Using X-ray absorption fine structure spectroscopy, both EXAFS and XANES, the cation distributions in NiFe 2O 4 particles dispersed in a corrosion product deposit layer have been studied. The specimen was obtained from a selected fuel rod used in a commercial boiling water reactor plant. EXAFS data allowed the quantitative determination of specific site distributions for all transition metal cations in Ni-ferrite deposits. The results show that the analyzed NiFe 2O 4 particles do not have a totally inverted spinel structure. The relative occupancy of iron and nickel cations in the tetrahedral and octahedral sites of the spinel lattice is determined from the measured data.

  17. Relevance of glycosylation of S-layer proteins for cell surface properties

    PubMed Central

    Schuster, Bernhard; Sleytr, Uwe B.

    2015-01-01

    Elucidating the building principles and intrinsic features modulating certain water-associated processes (e.g., surface roughness in the nanometer scale, surface hydration and accompanied antifouling property, etc.) of surface structures from (micro)organisms is nowadays a highly challenging task in fields like microbiology, biomimetic engineering and (bio)material sciences. Here, we show for the first time the recrystallization of the wild-type S-layer glycoprotein wtSgsE from Geobacillus stearothermophilus NRS 2004/3a and its recombinantly produced non-glycosylated form, rSgsE, on gold sensor surfaces. Whereas the proteinaceous lattice of the S-layer proteins is forming a rigid layer on the sensor surface, the glycan chains are developing an overall soft, highly dissipative film. Interestingly, to the wtSgsE lattice almost twice the amount of water is bound and/or coupled in comparison with the non-glycosylated rSgsE with the preferred region being the extending glycan residues. The present results are discussed in terms of the effect of the glycan residues on the recrystallization, the adjoining hydration layer, and the nanoscale roughness and fluidic behavior. The latter features may turn out to be one of the most general ones among bacterial and archaeal S-layer lattices. PMID:25818946

  18. The effect of nanostructured surface layer on the fatigue behaviors of a carbon steel

    NASA Astrophysics Data System (ADS)

    Li, D.; Chen, H. N.; Xu, H.

    2009-01-01

    A nanostructured surface layer was formed on a carbon steel by means of surface mechanical attrition treatment (SMAT). The microstructure of the surface layer of the SMATed sample was characterized by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Microhardness and residual stress distribution along the depth from the SMATed surface layer were measured at the same time. Fatigue behaviors of the carbon steel subjected to the SMAT process were investigated. A nanostructured layer with average grains size of ˜12.7 nm was formed, of which microhardness is more than twice as high as that in matrix and residual compressive stress can reach about -400 MPa with maximum depth of ˜600 ?m. The fatigue strength of as-received sample is 267 MPa and that of SMATed sample is 302 MPa based on fatigue life 5 × 10 6 cycles. The SMAT process has improved the fatigue strength by as much as 13.1% for the carbon steel. It is shown that the SMAT is an effective method to render the material with the features, such as a nanostructured and work-hardened surface layer as well as compressive residual stresses, which can pronouncedly improve the fatigue strength of the carbon steel.

  19. An investigation in the variance in particle surface interactions and their effects in gas turbines

    SciTech Connect

    Hamed, A. (Dept. of Aerospace Engineering and Engineering Mechanics, Univ. of Cincinnati, Cincinnati, OH (US))

    1992-04-01

    This paper presents the results of a study conducted to investigate particle surface interaction characteristics and their effects on the particle dynamics and blade erosion in axial flow gas turbines. The particle restitution velocities measured experimentally using Laser Doppler Velocimetry in a special tunnel are analyzed using statistical methods. The resulting distribution functions of the rebounding particle velocities after surface impacts are introduced in the particle trajectory simulations through the turbine blade passages, suing a methodology that combines particle dynamics computations in a probabilistic model. The presented results for the simulated ash particle dynamics demonstrate the effect of the experimentally measured variance in the particle restitution characteristics on the particle surface impacts, and the associated blade erosion in an axial flow turbine.

  20. Influence of transverse surface waves on turbulent boundary layers

    NASA Technical Reports Server (NTRS)

    Balasubramanian, R.; Ash, R. L.; Cary, A. M., Jr.; Bushnell, D. M.

    1977-01-01

    Wavy wall experiments using solid waves and progressive waves have been reported. For this paper, the major effects of waviness of the wall on the flow are identified as due to oscillatory curvature (convex-concavity) and oscillatory acceleration/deceleration of the flow, which imposes a highly nonequilibrium influence upon the turbulence structure. The theoretical analysis in this presentation takes into account proper turbulence modeling (including the nonequilibrium effects) for the wavy wall problem. The analysis proceeds in three stages: (1) inviscid solution for induced pressure due to the physical wall, (2) solution of a turbulent boundary layer with pressure gradients and curvature effects in the modeling from which the profile correction is computed, and (3) induced pressure computations for the corrected profile. The phase shift of pressure perturbations with respect to the physical wall can be predicted, and pressure drag and skin friction drag can be estimated, with nonlinear viscous effects included. Comparison of the theoretical estimates with experimental data are also presented.

  1. Computed and experimental interactions between eddy structure and dispersed particles in developing free shear layers

    SciTech Connect

    Buckingham, A.C.; Siekhaus, W.J.; Keller, J.O.; Ellzey, J.; Hubbard, G.; Daily, J.W.

    1982-05-20

    We are investigating the interactive process between turbulent flow and dispersed phase particles. We are focusing on the mechanisms that appear to result in a reduction of local turbulent intensity and a corresponding reduction in wall heat transfer and subsequent wall erosion in turbulent solid propellant combustion flow. We apply computational simulations and physical experiments specialized to a developing free shear layer over a rearward facing step and over a parallel splitter plate. The flow configuration evolves in a two-dimensional, steady, combustion and non-combustion turbulent free shear mixing region, with and without particle additives. The computational simulations combine three basic components: gas phase Navier-Stokes solutions, Lagrange particle field solutions and a Monte Carlo technique for the random encounters, forces and accelerations between the two fields. We concentrate here on relatively large sized additive particles (of the order of tens of microns to 100 microns mean diameter). We examine their apparent influence in breaking up the larger, energy bearing eddy structures into smaller structures which are more readily dissipated.

  2. Optical measurements of surface oxide layer formation on metal films

    SciTech Connect

    Scott, M.L.

    1987-01-01

    We have employed two optical techniques which give complementary indications of the formation of monolayers of oxide on freshly evaporated aluminum and silicon thin films. Visible ellipsometry is utilized to observe the growth of the initial monolayer of oxide on these films. From these data, we deduce the pressure and coverage dependence as well as the growth rate for the initial monolayer arising from these surface reactions. In addition, extreme ultraviolet (xuv) reflectance vs angle of incidence measurements at 58.4 nm wavelength clearly indicate the growth of oxide on the surface of our freshly deposited aluminum and silicon films as well. We have utilized this reflectance data to deduce the optical constants of aluminum and silicon at 58.4 nm. We find that previous xuv measurements of these optical constants were hampered by the presence of oxides. We also determined that the xuv reflectivity performance of aluminum films freshly deposited in our uhv system does not degrade appreciably when stored for four weeks in a helium atmosphere of 2 x 10/sup -9/ Torr. 11 refs., 7 figs., 1 tab.

  3. The measurement of boundary layers on a compressor blade in cascade. III - Pressure surface boundary layers and the near wake

    NASA Technical Reports Server (NTRS)

    Deutsch, Steven; Zierke, William C.

    1987-01-01

    A one-component laser Doppler velocimeter (LDV) has been used to measure the two-dimensional periodic flow field about a double circular arc, compressor blade in cascade. Eleven boundary layer profiles were taken on both the pressure and suction surfaces of the blade, and two profiles were taken in the near wake. In this part of the study, the detailed LDV studies are described. The measurements indicate that the onset of transition occurs near 60 percent chord. The lack of a logarithmic region in the data measured at 97.9 percent chord indicates that transition is not complete. The thin laminar boundary layers near the leading edge led to some measurement problems, characterized by large turbulence intensities, in using the LDV.

  4. The importance of a surface organic layer in simulating permafrost thermal and carbon dynamics

    NASA Astrophysics Data System (ADS)

    Jafarov, E.; Schaefer, K.

    2015-06-01

    Permafrost-affected soils contain twice as much carbon as currently exists in the atmosphere. Studies show that warming of the perennially frozen ground could initiate significant release of the frozen soil carbon into the atmosphere. To reduce the uncertainty associated with the modeling of the permafrost carbon feedback it is important to start with the observed soil carbon distribution and to better address permafrost thermal and carbon dynamics. We used the recent Northern Circumpolar Soil Carbon Dataset to simulate present soil organic carbon (SOC) distribution in permafrost-affected soils under the steady state climate forcing. We implemented a dynamic surface organic layer with vertical carbon redistribution and dynamic root growth controlled by active layer thickness to improve modeling of the permafrost thermodynamics. Our results indicate that a dynamic surface organic layer improved permafrost thermal dynamics and simulated active layer thickness, allowing better simulation of the observed SOC densities and their spatial distribution.

  5. Effects of Dynamic Forcings and Surface Fluxes In The Nocturnal Boundary Layer Simulation

    NASA Astrophysics Data System (ADS)

    Soler, M. R.; Conangla, L.; Cuxart, J.; Terradellas, E.

    The main purpose of this study is to simulate with a second order turbulence model, the main features of the stable nocturnal boundary layer, as the presence of the low-level jets, intermittent turbulence, and elevated turbulent layers decoupled from the surface. These simulations have been done with data collected during SABLES98 (Stable At- mospheric Boundary Layer Experiment in Spain), which took place in September of 1998, from 10th to 27th in the northern Castilla Plateau. The results show that the model reproduce fairly accurately the observations, nevertheless, especial attention is paid on explore the effects of dynamic forcings and surface fluxes on the evolution of the vertical turbulence structures within the nocturnal Boundary Layer.

  6. Influence of surface forcing on near-surface and mixing layer turbulence in the tropical Indian Ocean

    NASA Astrophysics Data System (ADS)

    Callaghan, Adrian H.; Ward, Brian; Vialard, Jérôme

    2014-12-01

    An autonomous upwardly-moving microstructure profiler was used to collect measurements of the rate of dissipation of turbulent kinetic energy (?) in the tropical Indian Ocean during a single diurnal cycle, from about 50 m depth to the sea surface. This dataset is one of only a few to resolve upper ocean ? over a diurnal cycle from below the active mixing layer up to the air-sea interface. Wind speed was weak with an average value of ~5 m s-1 and the wave field was swell-dominated. Within the wind and wave affected surface layer (WWSL), ? values were on the order of 10-7-10-6 W kg-1 at a depth of 0.75 m and when averaged, were almost a factor of two above classical law of the wall theory, possibly indicative of an additional source of energy from the wave field. Below this depth, ? values were closer to wall layer scaling, suggesting that the work of the Reynolds stress on the wind-induced vertical shear was the major source of turbulence within this layer. No evidence of persistent elevated near-surface ? characteristic of wave-breaking conditions was found. Profiles collected during night-time displayed relatively constant ? values at depths between the WWSL and the base of the mixing layer, characteristic of mixing by convective overturning. Within the remnant layer, depth-averaged values of ? started decaying exponentially with an e-folding time of 47 min, about 30 min after the reversal of the total surface net heat flux from oceanic loss to gain.

  7. The role of modifying molecular chains in the formation of organized molecular films of organo-modified nanodiamond: construction of a highly ordered low defect particle layer and evaluation of desorption behavior of organic chains.

    PubMed

    Fujimori, Atsuhiro; Kasahara, Yusuke; Honda, Nanami; Akasaka, Shuichi

    2015-03-10

    The role of organo-modifying molecular chains in the formation of molecular films of organo-modified nanodiamond is discussed herein based on interfacial chemical particle integration of organo-modified nanodiamond having a particle size of 5 nm. The surface of nanodiamond is known to be covered with a nanolayer of adsorbed water. This water nanolayer was exploited for organo-modification of nanodiamond with long-chain fatty acids via adsorption, leading to nanodispersion of nanodiamond in general organic solvents as a mimic of solvency. The organo-modified nanodiamond dispersed "solution" was used as a spreading solution for depositing a mono-"particle" layer on the water surface, and a Langmuir particle layer was integrated at the air/water interface. Multi-"particle" layers were then formed via the Langmuir-Blodgett technique and were subjected to fine structural analysis. The effect of organo-modification enabled integration and multilayer formation of inorganic nanoparticles due to enhancement of the van der Waals interactions between the chains. That is to say, the "encounter" between the organo-modifying chain and the inorganic particles led to solubilization of the inorganic particles and enhanced interactions between the particles, which can be regarded as imparting new function to the organic molecules. The morphology of the single-particle layer was maintained after removal of the organic region of the composite via the baking process, whereas the regularity of the layered period was disordered. Thus, the organic chains are essential as modifiers for maintenance of the layered structure. PMID:25692757

  8. Heat balances of the surface mixed layer in the equatorial Atlantic and Indian Ocean during FGGE

    NASA Technical Reports Server (NTRS)

    Molinari, R. L.

    1985-01-01

    Surface meteorological and surface and subsurface oceanographic data collected during FGGE in the equatorial Atlantic and Indian Oceans are used to estimate the terms in a heat balance relation for the mixed layer. The first balance tested is between changes in mixed layer temperature (MLT) and surface energy fluxes. Away from regions of low variance in MLT time series and equatorial and coastal upwelling, surface fluxes can account for 75 percent of the variance in the observed time series. Differences between observed and estimated MLTs indicate that on the average, maximum errors in surface flux are of the order of 20 to 30 W/sq m. In the Atlantic, the addition of zonal advection does not significantly improve the estimates. However in regions of equatorial upwelling, the eastern Atlantic vertical mixing and meridional advection can play an important role in the evolution of MLTs.

  9. Surface electron accumulation in indium nitride layers grown by high pressure chemical vapor deposition

    Microsoft Academic Search

    R. P. Bhatta; B. D. Thoms; M. Alevli; N. Dietz

    2007-01-01

    Surface termination and electronic properties of InN layers grown by high pressure chemical vapor deposition have been studied by high resolution electron energy loss spectroscopy (HREELS). HREEL spectra from InN after atomic hydrogen cleaning show N–H termination with no indium overlayer or droplets and indicate that the layer is N-polar. Broad conduction band plasmon excitations are observed centered at 3400cm?1

  10. Acoustic receptivity due to weak surface inhomogeneities in adverse pressure gradient boundary layers

    Microsoft Academic Search

    Meelan Choudhari; Lian Ng; Craig Streett

    1995-01-01

    The boundary layer receptivity to free-stream acoustic waves in the presence of localized surface disturbances is studied for the case of incompressible Falkner-Skan flows with adverse pressure gradients. These boundary layers are unstable to both viscous and inviscid (i.e., inflectional) modes, and the finite Reynolds number extension of the Goldstein-Ruban theory provides a convenient method to compare the efficiency of

  11. Preparation and characterization of ultrathin dual-layer ionic liquid lubrication film assembled on silica surfaces

    Microsoft Academic Search

    Jibin Pu; Liping Wang; Yufei Mo; Qunji Xue

    2011-01-01

    A novel ultrathin dual-layer film, which contained both bonded and mobile phases in ionic liquids (ILs) layer, was fabricated successfully on a silicon substrate modified by a self-assembled monolayer (SAM). The formation and surface properties of the films were analyzed using ellipsometer, water contact angle meter, attenuated total reflectance Fourier transform infrared spectroscopy, multi-functional X-ray photoelectron spectroscopy, and atomic force

  12. Controlling the hydrophilicity and contact resistance of fuel cell bipolar plate surfaces using layered nanoparticle assembly

    Microsoft Academic Search

    Feng Wang

    2010-01-01

    Hybrid nanostructured coatings exhibiting the combined properties of electrical conductivity and surface hydrophilicity were obtained by using Layer-by-Layer (LBL) assembly of cationic polymer, silica nanospheres, and carbon nanoplatelets. This work demonstrates that by controlling the nanoparticle zeta (zeta) potential through the suspension parameters (pH, organic solvent type and amount, and ionic content) as well as the assembly sequence, the nanostructure

  13. Investigation of surface topology of printed nanoparticle layers using wide-angle low-Q scattering.

    PubMed

    Jonah, Emmanuel O; Härting, Margit; Gullikson, Eric; Aquila, Andrew; Britton, David T

    2014-05-01

    A new small-angle scattering technique in reflection geometry is described which enables a topological study of rough surfaces. This is achieved by using long-wavelength soft X-rays which are scattered at wide angles but in the low-Q range normally associated with small-angle scattering. The use of nanometre-wavelength radiation restricts the penetration to a thin surface layer which follows the topology of the surface, while moving the scattered beam to wider angles preventing shadowing by the surface features. The technique is, however, only applicable to rough surfaces for which there is no specular reflection, so that only the scattered beam was detected by the detector. As an example, a study of the surfaces of rough layers of silicon produced by the deposition of nanoparticles by blade-coating is presented. The surfaces of the blade-coated layers have rough features of the order of several micrometers. Using 2 nm and 13 nm X-rays scattered at angular ranges of 5° ? ? ? 51° and 5° ? ? ? 45°, respectively, a combined range of scattering vector of 0.00842 Å(-1) ? Q ? 0.4883 Å(-1) was obtained. Comparison with previous transmission SAXS and USAXS studies of the same materials indicates that the new method does probe the surface topology rather than the internal microstructure. PMID:24763644

  14. Turbulent flow over a surface-mounted 2-D block in thermally-stratified boundary layers

    NASA Astrophysics Data System (ADS)

    Zhang, W.; Markfort, C. D.; Porte-Agel, F.

    2013-12-01

    Turbulent boundary-layer flows over complex topography have been of great interest in the atmospheric sciences and wind engineering communities. The geometry of the topography, surface characteristics and atmospheric thermal stability play important roles in determining momentum and scalar flux distribution. Studies of turbulent flow over simplified topography, such as 2-D or 3-D blocks and 2-D or 3-D sinusoidal hills, conducted under neutrally stratified boundary-layer conditions have provided insightful information of fluid dynamics. However, atmospheric thermal stability has rarely been incorporated into laboratory simulations, in particular, wind-tunnel experiments. Extension of such studies in thermally-stratified wind tunnels will fill this gap and advance our understanding of the underlying physics of flow over complex topography. Additionally, experimental data are useful for the development of new parameterizations for surface fluxes and validation of numerical models such as Large-Eddy Simulation (LES). A series of experiments involving neutral and thermally-stratified boundary-layer flows over a surface-mounted 2-D block, conducted at the Saint Anthony Falls Laboratory boundary-layer wind tunnel, will be presented. The 2-D block, with a width to height ratio of 2:1, occupied the lowest 25% of the turbulent boundary layer. Thermal stratification of the boundary layer was achieved by independently controlling the temperature of both the airflow, the test section floor and block surfaces. Measurements using high-resolution PIV, x-wire/cold-wire anemometry, thermal-couples and surface heat flux sensors were made to identify and quantify the turbulent flow properties, including the size of the recirculation zone, coherent vortex structures and the subsequent boundary layer recovery. Emphasis will be put on addressing thermal stability effects on momentum and scalar flux distribution.

  15. Synthesis and sorption properties of porous layers of cyclames on a modified polyvinyl chloride surface

    NASA Astrophysics Data System (ADS)

    Tsivadse, A. Yu.; Fridman, A. Ya.; Morozova, E. M.; Sokolova, N. P.; Voloshchuk, A. M.; Petukhova, G. A.; Bardyshev, I. I.; Gorbunov, A. M.; Polyakova, I. Ya.; Shapokhina, O. P.

    2012-03-01

    The structure and adsorption properties of the porous layers of synthesized ethanol-cyclames and sodium acetate cyclames on a surface of polyvinyl chloride (PVC) encapsulating fibers of the asbestos tissue of chrysotile asbestos are studied. It is established that PVC is linked to the silicon-oxygen chains of magnesium hydrosilicate; the capsule ensures the stability of the asbestos tissue under the action of the concentrated solutions of acids and alkalis; its exterior reproduces the fiber surface and has a typical microrelief; and there are voids in the layers. We conclude that the specific surface of layers and the volume of the adsorption space are larger than those of the initial fibers, and the statistical capacity upon the adsorption of water vapor and polar and nonpolar organic molecules depends on the nature and affinity for cyclames.

  16. Influence of surface steps on glide of threading dislocations during layer growth

    NASA Astrophysics Data System (ADS)

    Hoagland, R. G.; Hirth, J. P.; Misra, A.; Mitlin, D.

    2004-06-01

    We discuss the relaxation of coherency stresses by glide of threading dislocations in a layer that is growing coherently on a substrate. Glide of threading dislocations becomes energetically favorable when the thickness of the layer exceeds a critical value, hc. Predicted values of hc are often less than indicated by experimental observations. We show that the energy associated with the creation or removal of steps on the surface of a growing layer is important in determining the hc associated with glide of threading dislocations.

  17. Solid particles adsorbed on capillary-bridge-shaped fluid polystyrene surfaces.

    PubMed

    McEnnis, Kathleen; Dinsmore, Anthony D; Russell, Thomas P

    2015-05-19

    Particles adsorbed on microscopic polystyrene (PS) capillary bridge surfaces were observed to investigate their motion under capillary forces arising from a nonuniform shape. Capillary bridges were created by placing thin PS films, heated above the glass transition temperature (Tg), between two electrodes with an air gap between the surface of the PS and the upper electrode. Silica particles, 100 nm in diameter, were placed on the surface of the PS capillary bridges, and the sample was heated above the Tg of PS to enable particle motion. Samples were cooled to below Tg, and the locations of the particles were observed using scanning electron microscopy. The particles did not preferentially locate around the center of the capillary bridge, as predicted by others, but instead segregated to the edges. These results indicate that the forces driving particles to the three-phase contact line (air/PS/electrode surface) are greater than those locating particles around the center. PMID:25938879

  18. Interface magnetic coupling of Fe-phthalocyanine layers on a ferromagnetic surface

    NASA Astrophysics Data System (ADS)

    Annese, E.; Casolari, F.; Fujii, J.; Rossi, G.

    2013-02-01

    Fe-phthalocyanine (FePc) molecules bonded to metal surfaces form rehybridized interface states involving the Fe central atom reflected in changes of orbital and spin configuration. X-ray absorption spectroscopy and x-ray magnetic circular dichroism show the ferromagnetic coupling of the FePc molecules that are in contact with the Co(001) surface, even at room temperature (300 K), while the overgrown parallel layers of FePc in thicker molecular films are decoupled from the interface. The magnetized interface molecular layer reproduces the magnetic structures of the substrate (domains, patterns).

  19. Comparison of ambient particle surface area measurement by epiphaniometer and SMPS/APS

    NASA Astrophysics Data System (ADS)

    Shi, Ji Ping; Harrison, Roy M.; Evans, Douglas

    During measurement campaigns at an urban background and a rural site, simultaneous measurements of particle size distributions using a scanning mobility particle sizer (SMPS)/aerodynamic particle sizer (APS) combination and Fuchs surface using an epiphaniometer have been made. The epiphaniometer was calibrated using sub-100 nm monodisperse aerosol and it was found that a calibration based upon particle electrical mobility diameters measured with a SMPS was consistent irrespective of the use of singlet particles of sodium chloride and ammonium sulphate or clusters of carbon. The field intercomparison of surface areas derived directly from the epiphaniometer and calculated from the size distributions determined by the SMPS/APS combination showed a good agreement of Fuchs surface estimates at both measurement sites. However, attempts to estimate a "geometric" surface area from the epiphaniometer data led to significant divergence from the estimates of the SMPS/APS combination when there was a significant fraction of coarser (>700 nm) particles contributing to the aerosol surface area.

  20. Improvement and protection of niobium surface superconductivity by atomic layer deposition and heat treatment

    SciTech Connect

    Proslier, T.; /IIT, Chicago /Argonne; Zasadzinski, J.; /IIT, Chicago; Moore, J.; Pellin, M.; Elam, J.; /Argonne; Cooley, L.; /Fermilab; Antoine, C.; /Saclay

    2008-11-01

    A method to treat the surface of Nb is described, which potentially can improve the performance of superconducting rf cavities. We present tunneling and x-ray photoemission spectroscopy measurements at the surface of cavity-grade niobium samples coated with a 3 nm alumina overlayer deposited by atomic layer deposition. The coated samples baked in ultrahigh vacuum at low temperature degraded superconducting surface. However, at temperatures above 450 C, the tunneling conductance curves show significant improvements in the superconducting density of states compared with untreated surfaces.

  1. Improvement and protection of niobium surface superconductivity by atomic layer deposition and heat treatment.

    SciTech Connect

    Norem, J.; Proslier, T.; Zasadzinski, J.; Moore, J.; Elam, J.; Cooley, L.; Grey, K. E.; FNAL; Commissariat a l'energie Atomique

    2008-01-01

    A method to treat the surface of Nb is described, which potentially can improve the performance of superconducting rf cavities. We present tunneling and x-ray photoemission spectroscopy measurements at the surface of cavity-grade niobium samples coated with a 3 nm alumina overlayer deposited by atomic layer deposition. The coated samples baked in ultrahigh vacuum at low temperature degraded superconducting surface. However, at temperatures above 450 C, the tunneling conductance curves show significant improvements in the superconducting density of states compared with untreated surfaces.

  2. Particle Size Metrology: Comparison Between Aerosol Electrical Mobility and Laser Surface Light Scattering Techniques

    SciTech Connect

    Germer, Thomas A.; Mulholland, George W. [National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD 20899 (United States)

    2005-09-09

    Two different methods used to determine the size of polystyrene spheres were found to disagree by about 5 %. One of the methods, differential mobility analysis, measures particles in the aerosol phase, while the other, laser surface light scattering, measures them bound to a surface. It is believed that the observed discrepancy results from deformation of the particle when it is bound to the surface. The implications of such a deformation on scanning surface inspection system calibration is discussed.

  3. Kinetic multi-layer model of gas-particle interactions in aerosols and clouds (KM-GAP): linking condensation, evaporation and chemical reactions of organics, oxidants and water

    NASA Astrophysics Data System (ADS)

    Shiraiwa, M.; Pfrang, C.; Koop, T.; Pöschl, U.

    2012-03-01

    We present a novel kinetic multi-layer model for gas-particle interactions in aerosols and clouds (KM-GAP) that treats explicitly all steps of mass transport and chemical reaction of semi-volatile species partitioning between gas phase, particle surface and particle bulk. KM-GAP is based on the PRA model framework (Pöschl-Rudich-Ammann, 2007), and it includes gas phase diffusion, reversible adsorption, surface reactions, bulk diffusion and reaction, as well as condensation, evaporation and heat transfer. The size change of atmospheric particles and the temporal evolution and spatial profile of the concentration of individual chemical species can be modeled along with gas uptake and accommodation coefficients. Depending on the complexity of the investigated system and the computational constraints, unlimited numbers of semi-volatile species, chemical reactions, and physical processes can be treated, and the model shall help to bridge gaps in the understanding and quantification of multiphase chemistry and microphysics in atmospheric aerosols and clouds. In this study we demonstrate how KM-GAP can be used to analyze, interpret and design experimental investigations of changes in particle size and chemical composition in response to condensation, evaporation, and chemical reaction. For the condensational growth of water droplets, our kinetic model results provide a direct link between laboratory observations and molecular dynamic simulations, confirming that the accommodation coefficient of water at ~270 K is close to unity (Winkler et al., 2006). Literature data on the evaporation of dioctyl phthalate as a function of particle size and time can be reproduced, and the model results suggest that changes in the experimental conditions like aerosol particle concentration and chamber geometry may influence the evaporation kinetics and can be optimized for efficient probing of specific physical effects and parameters. With regard to oxidative aging of organic aerosol particles, we illustrate how the formation and evaporation of volatile reaction products like nonanal can cause a decrease in the size of oleic acid particles exposed to ozone.

  4. The Role of Contact Angle on the Depletion Layer when at the Interface Between Water and a Hydrophobic Surface

    NASA Astrophysics Data System (ADS)

    Poynor, Adele; Brown, Erin; Petersen, Shannon; McNany, Dylan

    2014-03-01

    By definition hydrophobic substances hate water. Water placed on a hydrophobic surface will form a drop in order to minimize its contact area. What happens when water is forced into contact with a hydrophobic surface? One theory is that an ultra-thin low-density depletion layer forms near the surface. We investigate the role of contact angle on depletion layer formation using the surface sensitive technique of Surface Plasmon Resonance

  5. The Role of Contact Angle on the Depletion Layer when at the Interface Between Water and a Hydrophobic Surface

    NASA Astrophysics Data System (ADS)

    Poynor, Adele; Petersen, Shannon; Ollander, Brooke

    2015-03-01

    By definition hydrophobic substances hate water. Water placed on a hydrophobic surface will form a drop in order to minimize its contact area. What happens when water is forced into contact with a hydrophobic surface? One theory is that an ultra-thin low-density depletion layer forms near the surface. We investigate the role of contact angle on depletion layer formation using the surface sensitive technique of Surface Plasmon Resonance.

  6. The sll1951 Gene Encodes the Surface Layer Protein of Synechocystis sp. Strain PCC 6803

    PubMed Central

    Trautner, Christoph

    2013-01-01

    Sll1951 is the surface layer (S-layer) protein of the cyanobacterium Synechocystis sp. strain PCC 6803. This large, hemolysin-like protein was found in the supernatant of a strain that was deficient in S-layer attachment. An sll1951 deletion mutation was introduced into Synechocystis and was easily segregated to homozygosity under laboratory conditions. By thin-section and negative-stain transmission electron microscopy, a ?30-nm-wide S-layer lattice covering the cell surface was readily visible in wild-type cells but was absent in the ?sll1951 strain. Instead, the ?sll1951 strain displayed a smooth lipopolysaccharide surface as its most peripheral layer. In the presence of chaotropic agents, the wild type released a large (>150-kDa) protein into the medium that was identified as Sll1951 by mass spectrometry of trypsin fragments; this protein was missing in the ?sll1951 strain. In addition, Sll1951 was prominent in crude extracts of the wild type, indicating that it is an abundant protein. The carotenoid composition of the cell wall fraction of the ?sll1951 strain was similar to that of the wild type, suggesting that the S-layer does not contribute to carotenoid binding. Although the photoautotrophic growth rate of the ?sll1951 strain was similar to that of the wild-type strain, the viability of the ?sll1951 strain was reduced upon exposure to lysozyme treatment and hypo-osmotic stress, indicating a contribution of the S-layer to the integrity of the Synechocystis cell wall. This work identifies the S-layer protein in Synechocystis and shows that, at least under laboratory conditions, this very abundant, large protein has a supportive but not a critical role in the function of the cyanobacterium. PMID:24078613

  7. Shear rheology of mixed protein adsorption layers vs their structure studied by surface force measurements.

    PubMed

    Danov, Krassimir D; Kralchevsky, Peter A; Radulova, Gergana M; Basheva, Elka S; Stoyanov, Simeon D; Pelan, Eddie G

    2014-05-01

    The hydrophobins are proteins that form the most rigid adsorption layers at liquid interfaces in comparison with all other investigated proteins. The mixing of hydrophobin HFBII with other conventional proteins is expected to reduce the surface shear elasticity and viscosity, Esh and ?sh, proportional to the fraction of the conventional protein. However, the experiments show that the effect of mixing can be rather different depending on the nature of the additive. If the additive is a globular protein, like ?-lactoglobulin and ovalbumin, the surface rigidity is preserved, and even enhanced. The experiments with separate foam films indicate that this is due to the formation of a bilayer structure at the air/water interface. The more hydrophobic HFBII forms the upper layer adjacent to the air phase, whereas the conventional globular protein forms the lower layer that faces the water phase. Thus, the elastic network formed by the adsorbed hydrophobin remains intact, and even reinforced by the adjacent layer of globular protein. In contrast, the addition of the disordered protein ?-casein leads to softening of the HFBII adsorption layer. Similar (an even stronger) effect is produced by the nonionic surfactant Tween 20. This can be explained with the penetration of the hydrophobic tails of ?-casein and Tween 20 between the HFBII molecules at the interface, which breaks the integrity of the hydrophobin interfacial elastic network. The analyzed experimental data for the surface shear rheology of various protein adsorption layers comply with a viscoelastic thixotropic model, which allows one to determine Esh and ?sh from the measured storage and loss moduli, G' and G?. The results could contribute for quantitative characterization and deeper understanding of the factors that control the surface rigidity of protein adsorption layers with potential application for the creation of stable foams and emulsions with fine bubbles or droplets. PMID:24828304

  8. Quasi-liquid layers on ice crystal surfaces are made up of two different phases

    PubMed Central

    Sazaki, Gen; Zepeda, Salvador; Nakatsubo, Shunichi; Yokomine, Makoto; Furukawa, Yoshinori

    2012-01-01

    Ice plays crucially important roles in various phenomena because of its abundance on Earth. However, revealing the dynamic behavior of quasi-liquid layers (QLLs), which governs the surface properties of ice crystals at temperatures near the melting point, remains an experimental challenge. Here we show that two types of QLL phases appear that exhibit different morphologies and dynamics. We directly visualized the two types of QLLs on ice crystal surfaces by advanced optical microscopy, which can visualize the individual 0.37-nm-thick elementary steps on ice crystal surfaces. We found that they had different stabilities and different interactions with ice crystal surfaces. The two immiscible QLL phases appeared heterogeneously, moved around, and coalesced dynamically on ice crystal surfaces. This picture of surface melting is quite different from the conventional picture in which one QLL phase appears uniformly on ice crystal surfaces. PMID:22232653

  9. Growth and characterization of ZnO multipods on functional surfaces with different sizes and shapes of Ag particles

    NASA Astrophysics Data System (ADS)

    A, Kamalianfar; S, A. Halim; Mahmoud Godarz, Naseri; M, Navasery; Fasih, Ud Din; J, A. M. Zahedi; Kasra, Behzad; K, P. Lim; A Lavari, Monghadam; S, K. Chen

    2013-08-01

    Three-dimensional ZnO multipods are successfully synthesized on functional substrates using the vapor transport method in a quartz tube. The functional surfaces, which include two different distributions of Ag nanoparticles and a layer of commercial Ag nanowires, are coated onto silicon substrates before the growth of ZnO nanostructures. The structures and morphologies of the ZnO/Ag heterostructures are investigated using X-ray diffraction and field emission scanning electron microscopy. The sizes and shapes of the Ag particles affect the growth rates and initial nucleations of the ZnO structures, resulting in different numbers and shapes of multipods. They also influence the orientation and growth quality of the rods. The optical properties are studied by photoluminescence, UV-vis, and Raman spectroscopy. The results indicate that the surface plasmon resonance strongly depends on the sizes and shapes of the Ag particles.

  10. Mechanical characteristics of SiC coating layer in TRISO fuel particles

    SciTech Connect

    Hosemann, Peter [ORNL] [ORNL; Martos, J. N. [University of California, Berkeley] [University of California, Berkeley; Frazer, D. [University of California, Berkeley] [University of California, Berkeley; Vasudevamurthy, Gokul [ORNL] [ORNL; Byun, Thak Sang [ORNL] [ORNL; Hunn, John D [ORNL] [ORNL; Jolly, Brian C [ORNL] [ORNL; Terrani, Kurt A [ORNL] [ORNL; Okuniewski, Maria A. [Idaho National Laboratory (INL)] [Idaho National Laboratory (INL)

    2013-01-01

    Tristructural isotropic (TRISO) particles are considered as advanced fuel forms for a variety of fission platforms. While these fuel structures have been tested and deployed in reactors, the mechanical properties of these structures as a function of production parameters need to be investigated in order to ensure their reliability during service. Nanoindentation techniques, indentation crack testing, and half sphere crush testing were utilized in order to evaluate the integrity of the SiC coating layer that is meant to prevent fission product release in the coated particle fuel form. The results are complimented by scanning electron microscopy (SEM) of the grain structure that is subject to change as a function of processing parameters and can alter the mechanical properties such as hardness, elastic modulus, fracture toughness and fracture strength. Through utilization of these advanced techniques, subtle differences in mechanical properties that can be important for in-pile fuel performance can be distinguished and optimized in iteration with processing science of coated fuel particle production.

  11. Mechanical characteristics of SiC coating layer in TRISO fuel particles

    NASA Astrophysics Data System (ADS)

    Hosemann, P.; Martos, J. N.; Frazer, D.; Vasudevamurthy, G.; Byun, T. S.; Hunn, J. D.; Jolly, B. C.; Terrani, K.; Okuniewski, M.

    2013-11-01

    Tristructural isotropic (TRISO) particles are considered as advanced fuel forms for a variety of fission platforms. While these fuel structures have been tested and deployed in reactors, the mechanical properties of these structures as a function of production parameters need to be investigated in order to ensure their reliability during service. Nanoindentation techniques, indentation crack testing, and half sphere crush testing were utilized in order to evaluate the integrity of the SiC coating layer that is meant to prevent fission product release in the coated particle fuel form. The results are complimented by scanning electron microscopy (SEM) of the grain structure that is subject to change as a function of processing parameters and can alter the mechanical properties such as hardness, elastic modulus, fracture toughness and fracture strength. Through utilization of these advanced techniques, subtle differences in mechanical properties that can be important for in-pile fuel performance can be distinguished and optimized in iteration with processing science of coated fuel particle production.

  12. Surface electrical properties of coal particles on interaction with polyelectrolytes

    SciTech Connect

    Evmenova, G.L. [Kuzbass State Technical University, Kemerovo (Russian Federation)

    2006-07-15

    The paper presents experimental data obtained in determining an electrokinetic potential of coal particles during their interaction with coagulation and flocculation agents. It is established that flocculation agents allow decreasing electrokinetic potential of mineral particles up to the values that promote aggregation of the particles thereby enabling the control over the stability of coal dispersions.

  13. Supramolecular Layer-by-Layer Assembly: Alternating Adsorptions of Guest and Host-Functionalized Molecules and Particles Using Multivalent Supramolecular Interactions

    Microsoft Academic Search

    Olga Crespo-Biel; Barbara Dordi; David N. Reinhoudt; Jurriaan Huskens

    2005-01-01

    The stepwise construction of a novel kind of self-assembled organic\\/inorganic multilayers based on multivalent supramolecular interactions between guest-functionalized dendrimers and host-modified gold nanoparticles has been developed, yielding supramolecular layer-by-layer assembly. The deposition process was monitored by surface plasmon resonance spectroscopy. Further characterization of the multilayer films was performed by means of UV\\/vis absorption spectroscopy, which showed a linear increase in

  14. Spectroscopic study on uranyl carboxylate complexes formed at the surface layer of Sulfolobus acidocaldarius.

    PubMed

    Reitz, Thomas; Rossberg, Andre; Barkleit, Astrid; Steudtner, Robin; Selenska-Pobell, Sonja; Merroun, Mohamed L

    2015-02-14

    The complexation of U(vi) at the proteinaceous surface layer (S-layer) of the archaeal strain Sulfolobus acidocaldarius was investigated over a pH range from pH 1.5 to 6 at the molecular scale using time-resolved laser-induced fluorescence spectroscopy (TRLFS) and U L(III)-edge extended X-ray absorption fine structure (EXAFS). The S-layer, which represents the interface between the cell and its environment, is very stable against high temperatures, proteases, and detergents. This allowed the isolation and purification of S-layer ghosts (= empty cells) that maintain the size and shape of the cells. In contrast to many other microbial cell envelope compounds the studied S-layer is not phosphorylated, enabling the investigation of uranyl carboxylate complexes formed at microbial surfaces. The latter are usually masked by preferentially formed uranyl phosphate complexes. We demonstrated that at highly acidic conditions (pH 1.5 to 3) no uranium was bound by the S-layer. In contrast to that, at moderate acidic pH conditions (pH 4.5 and 6) a complexation of U(vi) at the S-layer via deprotonated carboxylic groups was stimulated. Titration studies revealed dissociation constants for the carboxylic groups of glutamic and aspartic acid residues of pK(a) = 4.78 and 6.31. The uranyl carboxylate complexes formed at the S-layer did not show luminescence properties at room temperature, but only under cryogenic conditions. The obtained luminescence maxima are similar to those of uranyl acetate. EXAFS spectroscopy demonstrated that U(vi) in these complexes is mainly coordinated to carboxylate groups in a bidentate binding mode. The elucidation of the molecular structure of these complexes was facilitated by the absence of phosphate groups in the studied S-layer protein. PMID:25387060

  15. Boundary layer modeling of reactive flow over a porous surface with angled injection

    SciTech Connect

    Liu, Shiling; Fotache, Catalin G.; Hautman, Donald J.; Ochs, Stuart S. [United Technologies Research Center, MS 129-29, 411 Silver Lane, East Hartford, CT 06108 (United States); Chao, Beei-Huan [Department of Mechanical Engineering, University of Hawaii at Manoa, Honolulu, HI 96822 (United States)

    2008-08-15

    An analytical model was developed to investigate the dynamics of nonpremixed flames in a shear layer established between a mainstream flow of fuel-rich combustion products and a porous surface with an angled injection of air. In the model, a one-step overall chemical reaction was employed, together with boundary layer conservation equations solved using similarity solutions. Parametric studies were performed to understand the effects of equivalence ratio, temperature, and mass flow rate of the fuel and air streams on the flame standoff distance, surface temperature, and heat flux at the surface. The analytical model predictions were compared with computational fluid dynamics results obtained using the FLUENT commercial code for both the laminar and the turbulent flow models. Qualitative agreement in surface temperature was observed. Finally, the flame stability limits predicted by the model were compared with available experimental data and found to agree qualitatively, as well. (author)

  16. An exact solution of boundary layer flow over a moving surface embedded into a nanofluid in the presence of magnetic field and suction/injection

    NASA Astrophysics Data System (ADS)

    Elbashbeshy, E. M. A.; Emam, T. G.; Abdel-wahed, M. S.

    2014-01-01

    The effects of magnetic field, suction/injection, nanoparticles type, and nanoparticle volume fraction on heat transfer characteristics and mechanical properties of a moving surface embedded into cooling medium consists of water with Cu, Ag or Al2O3 particles are studied. The governing boundary layer equations are transformed to ordinary differential equations containing, suction/injection parameter, magnetic parameter, nanoparticle and volume fraction. These equations are solved analytically. The velocity and temperature profiles within the boundary layer are plotted and discussed in details for various values of the different parameters.

  17. Organic monolayers as resist layers for Cu deposition on Si (111) surfaces

    Microsoft Academic Search

    E. a Balaur; Y. a Zhang; T. a Djenizian; R. b Boukherroub; P.a Schmuki

    2006-01-01

    Organic covalently attached monolayers (CAMs) were found to be useful as resist layers for patterning Si surfaces. In the present work, we investigate selective plating of Cu on n-type Si (111) surfaces chemically modified with different organic monolayers and subsequently directly patterned by an electron-beam (e-beam) and by AFM induced scratching. The organic molecules (1-undecylenic acid, 1-decene and 1-octadecene) were

  18. Spectroscopic detection of atom-surface interactions in an atomic vapour layer with nanoscale thickness

    E-print Network

    Whittaker, K A; Hughes, I G; Sargsyan, A; Sarkisyan, D; Adams, C S

    2015-01-01

    We measure the resonance line shape of atomic vapor layers with nanoscale thickness confined between two sapphire windows. The measurement is performed by scanning a probe laser through resonance and collecting the scattered light. The line shape is dominated by the effects of Dicke narrowing, self-broadening, and atom-surface interactions. By fitting the measured line shape to a simple model we discuss the possibility to extract information about the atom-surface interaction.

  19. Numerical Simulation of Interaction of the Heavy Gas Cloud with the Atmospheric Surface Layer

    Microsoft Academic Search

    I. V. Kovalets; V. S. Maderich

    2006-01-01

    The numerical time-dependent three-dimensional model [Kovalets, I.V. and Maderich, V.S.: 2001, Int. J. Fluid Mech. Res. 30, 410–429] of the heavy gas dispersion in the atmospheric boundary layer has been improved by parameterizing momentum and\\u000a heat fluxes on the surface of Earth using Monin–Obukhov similarity theory. Three parameterizations of heat exchange with the\\u000a surface of Earth were considered: (A) formula

  20. Polymer drag reduction with surface roughness in flat-plate turbulent boundary layer flow

    Microsoft Academic Search

    H. L. Petrie; S. Deutsch; T. A. Brungart; A. A. Fontaine

    2003-01-01

    Experimental results from a study of surface roughness effects on polymer drag reduction in a zero-pressure gradient flat-plate turbulent boundary layer are presented. Both slot-injected polymer and homogeneous polymer ocean cases were considered over a range of flow conditions and surface roughness. Balance measurements of skin friction drag reduction are presented. Drag reductions over 60% were measured for both the

  1. The characteristics of turbulent velocity components in the surface layer under convective conditions

    Microsoft Academic Search

    H. A. Panofsky; H. Tennekes; D. H. Lenschow; J. C. Wyngaard

    1977-01-01

    It is proposed that the ratios of the standard deviations of the horizontal velocity components to the friction velocity in the surface layer under convective conditions depend only onzi\\/L wherezi is the height of the lowest inversion andL is the Monin-Obukhov length. This hypothesis is tested by using observations from several data sets over uniform surfaces and appears to fit

  2. Impact of surface heterogeneity on a buoyancy-driven convective boundary layer in light winds

    Microsoft Academic Search

    Dominique Courault; Philippe Drobinski; Yves Brunet; Pierre Lacarrere; Charles Talbot

    2007-01-01

    Land-use practices such as deforestation or agricultural management may affect regional climate, ecosystems and water resources.\\u000a The present study investigates the impact of surface heterogeneity on the behaviour of the atmospheric boundary layer (ABL),\\u000a at a typical spatial scale of 1 km. Large-eddy simulations, using an interactive soil–vegetation–atmosphere surface scheme,\\u000a are performed to document the structure of the three-dimensional flow, as

  3. Distribution of icy particles across Enceladus' surface as derived from Cassini-VIMS measurements

    USGS Publications Warehouse

    Jaumann, R.; Stephan, K.; Hansen, G.B.; Clark, R.N.; Buratti, B.J.; Brown, R.H.; Baines, K.H.; Newman, S.F.; Bellucci, G.; Filacchione, G.; Coradini, A.; Cruikshank, D.P.; Griffith, C.A.; Hibbitts, C.A.; McCord, T.B.; Nelson, R.M.; Nicholson, P.D.; Sotin, C.; Wagner, R.

    2008-01-01

    The surface of Enceladus consists almost completely of water ice. As the band depths of water ice absorptions are sensitive to the size of particles, absorptions can be used to map variations of icy particles across the surface. The Visual and Infrared Mapping Spectrometer (VIMS) observed Enceladus with a high spatial resolution during three Cassini flybys in 2005 (orbits EN 003, EN 004 and EN 011). Based on these data we measured the band depths of water ice absorptions at 1.04, 1.25, 1.5, and 2 ??m. These band depths were compared to water ice models that represent theoretically calculated reflectance spectra for a range of particle diameters between 2 ??m and 1 mm. The agreement between the experimental (VIMS) and model values supports the assumption that pure water ice characterizes the surface of Enceladus and therefore that variations in band depth correspond to variations in water ice particle diameters. Our measurements show that the particle diameter of water ice increases toward younger tectonically altered surface units with the largest particles exposed in relatively "fresh" surface material. The smallest particles were generally found in old densely cratered terrains. The largest particles (???0.2 mm) are concentrated in the so called "tiger stripes" at the south pole. In general, the particle diameters are strongly correlated with geologic features and surface ages, indicating a stratigraphic evolution of the surface that is caused by cryovolcanic resurfacing and impact gardening. ?? 2007 Elsevier Inc. All rights reserved.

  4. The dynamic deformation of a layered viscoelastic medium under surface excitation

    NASA Astrophysics Data System (ADS)

    Aglyamov, Salavat R.; Wang, Shang; Karpiouk, Andrei B.; Li, Jiasong; Twa, Michael; Emelianov, Stanislav Y.; Larin, Kirill V.

    2015-06-01

    In this study the dynamic behavior of a layered viscoelastic medium in response to the harmonic and impulsive acoustic radiation force applied to its surface was investigated both theoretically and experimentally. An analytical solution for a layered viscoelastic compressible medium in frequency and time domains was obtained using the Hankel transform. A special incompressible case was considered to model soft biological tissues. To verify our theoretical model, experiments were performed using tissue-like gel-based phantoms with varying mechanical properties. A 3.5?MHz single-element focused ultrasound transducer was used to apply the radiation force at the surface of the phantoms. A phase-sensitive optical coherence tomography system was used to track the displacements of the phantom surface. Theoretically predicted displacements were compared with experimental measurements. The role of the depth dependence of the elastic properties of a medium in its response to an acoustic pulse at the surface was studied. It was shown that the low-frequency vibrations at the surface are more sensitive to the deep layers than high-frequency ones. Therefore, the proposed model in combination with spectral analysis can be used to evaluate depth-dependent distribution of the mechanical properties based on the measurements of the surface deformation.

  5. 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.

  6. 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.

  7. A Unified Account of Perceptual Layering and Surface Appearance in Terms of Gamut Relativity

    PubMed Central

    Vladusich, Tony; McDonnell, Mark D.

    2014-01-01

    When we look at the world—or a graphical depiction of the world—we perceive surface materials (e.g. a ceramic black and white checkerboard) independently of variations in illumination (e.g. shading or shadow) and atmospheric media (e.g. clouds or smoke). Such percepts are partly based on the way physical surfaces and media reflect and transmit light and partly on the way the human visual system processes the complex patterns of light reaching the eye. One way to understand how these percepts arise is to assume that the visual system parses patterns of light into layered perceptual representations of surfaces, illumination and atmospheric media, one seen through another. Despite a great deal of previous experimental and modelling work on layered representation, however, a unified computational model of key perceptual demonstrations is still lacking. Here we present the first general computational model of perceptual layering and surface appearance—based on a boarder theoretical framework called gamut relativity—that is consistent with these demonstrations. The model (a) qualitatively explains striking effects of perceptual transparency, figure-ground separation and lightness, (b) quantitatively accounts for the role of stimulus- and task-driven constraints on perceptual matching performance, and (c) unifies two prominent theoretical frameworks for understanding surface appearance. The model thereby provides novel insights into the remarkable capacity of the human visual system to represent and identify surface materials, illumination and atmospheric media, which can be exploited in computer graphics applications. PMID:25402466

  8. Sensitivity of climate simulations to land-surface and atmospheric boundary-layer treatments - a review

    SciTech Connect

    Garratt, J.R. (CSIRO Division of Atmospheric Research, Victoria (Australia))

    1993-03-01

    Aspects of the land-surface and boundary-layer treatments in 20 or so atmospheric general circulation models (GCMs) are summarized. only a few of these have had significant sensitivity studies published. The sensitivity studies focus upon the parameterization of land- surface processes and specification of land-surface properties including albedo, roughness length, soil moisture status, and vegetation density. The impacts of surface albedo and soil moisture upon the climate simulated in GCMs with bare-soil land surfaces are well known. Continental evaporation and precipitation tend to decrease with increased albedo and decreased soil moisture availability. Few conclusive studies have been carried out on the impact of a gross roughness-length change. A canopy scheme in a GCM ensures the combined impacts of roughness, albedo, and soil-moisture availability upon the simulated climate. The most revealing studies to date involve the regional impact of Amazonian deforestation. Four studies show that replacing tropical forest with a degraded pasture results in decreased evaporation and precipitation, and increased near-surface air temperatures. Sensitivity studies suggest the need for a realistic surface representation in general circulation models of the atmosphere. It is not yet clear how detailed this representation needs to be, but the parameterization of boundary-layer and convective clouds probably represents a greater challenge to improved climate simulations. This is illustrated in the case of surface net radiation for Amazonia, which is not well simulated and tends to be overestimated, leading to evaporation rates that are too large. Underestimates in cloudiness, cloud albedo, and clear-sky shortwave absorption, rather than in surface albedo, appear to be the main culprits. Three major tasks for the researcher of development and validation of atmospheric boundary-layer and surface schemes are detailed.

  9. Using of standard marine radar for determination of a water surface and an atmosphere near-surface layer parameters

    NASA Astrophysics Data System (ADS)

    Bogatov, Nikolay A.; Bakhanov, Victor V.; Ermoshkin, Aleksei V.; Kazakov, Vasily I.; Kemarskaya, Olga N.; Titov, Victor I.; Troitskaya, Yulia I.

    2014-10-01

    At present time radar methods of the seas and oceans diagnostics are actively developing. Using of the radar stations based on satellites and planes allows to receive information on a sea surface and a atmosphere near-surface layer with coverage of big water surface areas independently of day time. The developed methods of satellite radio images processing can be applied to marine radar stations. In Institute of Applied Physics RAS works on sea surface diagnostics systems development on the basis of standard marine radar are actively conducted. Despite smaller coverage of the territory in comparison with satellite data, marine radar have possibility to record spatially temporary radar images and to receive information on a surrounding situation quickly. This work deals with results of the researches which were conducted within the international expedition in the Atlantic Ocean in the autumn of 2012 on a route Rotterdam (Netherlands) - Ushuaya (Argentina) - Antarctica — Ushuaya. During this expedition a complex measurements of a sea surface, a atmosphere near-surface layer parameters and subsurface currents in the wide range of hydroweather conditions, including the storm were carried out. The system developed in IAP RAS on the basis of a marine radar ICOM MR-1200RII and the ADC (Analog Digital Converter) block for data recording on the personal computer was used. Display of a non-uniform near-surface current on sea surface radar images in storm conditions is shown. By means of the high-speed anemometer and meteorological station the measurements of the atmosphere parameters were carried out. Comparison of the anemometer data with calculated from radar images is carried out. Dependence of radar cross section from wind speed in the wide range of wind speeds, including storm conditions is investigated. Possibility of marine radar using for surface waves intensity and ice situation estimates also as icebergs detection is shown.

  10. Production and cell surface display of recombinant anthrax protective antigen on the surface layer of attenuated Bacillus anthracis.

    PubMed

    Wang, Yan-chun; Yuan, Sheng-ling; Tao, Hao-xia; Wang, Ling-chun; Zhang, Zhao-shan; Liu, Chun-jie

    2015-02-01

    To investigate the surface display of the anthrax protective antigen (PA) on attenuated Bacillus anthracis, a recombinant B. anthracis strain, named AP429 was constructed by integrating into the chromosome a translational fusion harboring the DNA fragments encoding the cell wall-targeting domain of the S-layer protein EA1 and the anthrax PA. Crerecombinase action at the loxP sites excised the antibiotic marker. Western blot analysis, fluorescence-activated cell sorting and immunofluorescence analysis confirmed that PA was successfully expressed on the S-layer of the recombinant antibiotic marker-free strain. Notwithstanding extensive proteolytic degradation of the hybrid protein SLHs-PA, quantitative ELISA revealed that approximately 8.1 × 10(6) molecules of SLHs-PA were gained from each Bacillus cell. Moreover, electron microscopy assay indicated that the typical S-layer structures could be clearly observed from the recombinant strain micrographs. PMID:25504373

  11. Synthesis and assembly of hepatitis B virus surface antigen particles in yeast

    Microsoft Academic Search

    Pablo Valenzuela; Angelica Medina; William J. Rutter; Gustav Ammerer; Benjamin D. Hall

    1982-01-01

    The surface antigen of hepatitis B virus (HBsAg) has been synthesized in the yeast Saccharomyces cerevisiae by using an expression vector that employs the 5'-flanking region of yeast alcohol dehydrogenase I as a promoter to transcribe surface antigen coding sequences. The protein synthesized in yeast is assembled into particles having properties similar to the 22-nm particles secreted by human cells.

  12. Surface particle sizes on armoured gravel streambeds: effects of supply and hydraulics

    Microsoft Academic Search

    Peter J. Whiting; John G. King

    2003-01-01

    Most gravel-bed streams exhibit a surface armour in which the median grain size of the surface particles is coarser than that of the subsurface particles. This armour has been interpreted to result when the supply of sediment is less than the ability of the stream to move sediment. While there may be certain sizes in the bed for which the

  13. Manipulating particle trajectories with phase-control in surface acoustic wave microfluidics

    E-print Network

    Rubloff, Gary W.

    Manipulating particle trajectories with phase-control in surface acoustic wave microfluidics Nathan microfluidic flow mixer Biomicrofluidics 6, 012803 (2012) Cell separation and transportation between two particle trajectories with phase-control in surface acoustic wave microfluidics Nathan D. Orloff,1 Jaclyn R

  14. The Effect of Entrapped Bone Particles on the Surface Morphology and Wear of Polyethylene

    Microsoft Academic Search

    Kimberly D. Mimnaugh; Jian Q. Yao; Michel P. Laurent; Roy Crowninshield; James J. Mason; Cheryl Blanchard

    2009-01-01

    Clinically retrieved highly cross-linked ultrahigh molecular weight polyethylene (HXPE) acetabular liners have demonstrated scratching, whereas conventional ultrahigh-molecular-weight polyethylene (UHMWPE) implants show a smoother surface early after implantation. In the present study, the potential of bone particles and soft tissues, rather than cement, to scratch the articular surface of HXPE and UHMWPE (? radiated) acetabular components was evaluated; multiple bone particles

  15. Interaction of silica nano-particles with a flat silica surface through neutron reflectometry

    SciTech Connect

    Chung, Eunhyea [Georgia Institute of Technology; Yiacoumi, Sotira [Georgia Institute of Technology; Halbert, Candice E [ORNL; Ankner, John Francis [ORNL; Wang, Wei [ORNL; Tsouris, Costas [ORNL

    2012-01-01

    Neutron reflectometry (NR) was employed to study the interaction of nanosized silica particles with a flat silica surface in aqueous solutions. Unlike other experimental tools that are used to study surface interactions, NR can provide information on the particle density profile in the solution near the interface. Two types of silica particles (25 and 100 nm) were suspended in aqueous solutions of varying ionic strength. Theoretical calculations of the surface interaction potential between a particle and a flat silica surface using the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory were compared to the experimental data. The theory predicts that the potential energy is highly dependent on the ionic strength. In high ionic strength solutions, NR reveals a high concentration of particles near the flat silica surface. Under the same conditions, theoretical calculations show an attractive force between a particle and a flat surface. For low ionic strength solutions, the particle concentration near the surface obtained from NR is the same as the bulk concentration, while depletion of particles near the surface is expected because of the repulsion predicted by the DLVO theory.

  16. Electromagnetic force on a metallic particle in the presence of a dielectric surface

    Microsoft Academic Search

    P. C. Chaumet; M. Nieto-Vesperinas

    2000-01-01

    By using a method, previously established, to calculate electromagnetic fields, we compute the force of light upon a metallic particle. This procedure is based on both Maxwell's stress tensor and the couple dipole method. With these tools, we study the force when the particle is over a flat dielectric surface. The multiple interaction of light between the particle and the

  17. Numerical simulations of localized surface plasmons at a nano silver particle on a glass substrate

    Microsoft Academic Search

    Masanobu Haraguchi; Masahiko Noguchi; Masamitsu Fujii; Toshihiro Okamoto; Masuo Fukui

    2005-01-01

    We have performed numerical analysis of localized surface plasmons (LSP) at a nano silver particle on a glass substrate using the finite-difference time-domain method, taking into account the size dependence of the dielectric constants of silver. It was found that the characteristics of LSP at a nano metal particle depend on both shapes of the particles and a dielectric constant

  18. Examining Elemental Surface Enrichment in Ultrafine Aerosol Particles Using Analytical Scanning Transmission Electron Microscopy

    Microsoft Academic Search

    Andrew D. Maynard; Yasuo Ito; Ilke Arslan; Anthony T Zimmer; Nigel Browning; Alan Nicholls

    2004-01-01

    The surface structure and chemistry of ultrafine aerosol particles (typically particles smaller than 100 nm in diameter) play key roles in determining physical and chemical behavior, and is relevant to fields as diverse as nanotechnology and aerosol toxicity. Analytical scanning transmission electron microscopy (STEM) is one of the few analytical methods available that is potentially capable of characterizing ultrafine particles

  19. Computational simulation of salt transport and crystallization in surface layers of building envelopes

    NASA Astrophysics Data System (ADS)

    Ko?í, Václav; Mad?ra, Ji?í; ?erný, Robert

    2012-09-01

    A computational model of heat, moisture and salt transport in multi-layered systems of porous materials including salt crystallization is presented. A practical application of the model is illustrated for two different types of wall provided with interior and exterior plasters which are exposed to the climatic conditions characteristic for Central Europe. Temperature, water content, salt concentration and crystallized-salt amount fields are calculated for the time period of five years. Computational results show that water and salt transport parameters of both the load bearing structures and plasters play a very important role in the salt crystallization in surface layers. Lower transport parameters of materials of surface layers and higher transport parameters of materials of load bearing structures are found preferable.

  20. Application of the FEM for the prediction of the surface layer characteristics after shot peening

    Microsoft Academic Search

    M. Klemenz; V. Schulze; I. Rohr; D. Löhe

    2009-01-01

    A finite element (FE) simulation model is presented in order to serve as a fast prediction tool for the surface layer characteristics after shot peening. This includes a FE-geometry model and an elasto-viscoplastic combined isotropic kinematic material. For the detailed validation of its applicability simulated and experimentally measured topographies and residual stresses on plates of AISI 4140 in a quenched