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Sample records for hfo2 spherical particles

  1. PREPARATION OF SPHERICAL URANIUM DIOXIDE PARTICLES

    Science.gov (United States)

    Levey, R.P. Jr.; Smith, A.E.

    1963-04-30

    This patent relates to the preparation of high-density, spherical UO/sub 2/ particles 80 to 150 microns in diameter. Sinterable UO/sub 2/ powder is wetted with 3 to 5 weight per cent water and tumbled for at least 48 hours. The resulting spherical particles are then sintered. The sintered particles are useful in dispersion-type fuel elements for nuclear reactors. (AEC)

  2. Laser Pulse Heating of Spherical Metal Particles

    Directory of Open Access Journals (Sweden)

    Michael I. Tribelsky

    2011-12-01

    Full Text Available We consider the general problem of laser pulse heating of spherical metal particles with the sizes ranging from nanometers to millimeters. We employ the exact Mie solution of the diffraction problem and solve the heat-transfer equation to determine the maximum temperature rise at the particle surface as a function of optical and thermometric parameters of the problem. Primary attention is paid to the case when the thermal diffusivity of the particle is much larger than that of the environment, as it is in the case of metal particles in fluids. We show that, in this case, for any given duration of the laser pulse, the maximum temperature rise as a function of the particle size reaches a maximum at a certain finite size of the particle. We suggest simple approximate analytical expressions for this dependence, which cover the entire parameter range of the problem and agree well with direct numerical simulations.

  3. Optical properties of nanocrystalline HfO2 synthesized by an auto-igniting combustion synthesis

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    H. Padma Kumar

    2015-03-01

    Full Text Available The optical properties of nanocrystalline HfO2 synthesized using a single-step auto-igniting combustion technique is reported. Nanocrystalline hafnium oxide having particle size of the order 10–15 nm were obtained in the present method. The nanopowder was characterized using X-ray diffraction, Fourier transform infrared and Fourier transform Raman spectroscopic studies. All these studies confirm that the phase formation is complete in the combustion synthesis and monoclinic phase [P21/c(14] of HfO2 is obtained without the presence of any impurities or additional phases. The powder morphology of the as-prepared sample was studied using transmission electron microscopy and the results were in good agreement with that of the X-ray diffraction studies. The optical constants such as refractive index, extinction coefficient, optical conductivity and the band gap were estimated from UV–vis spectroscopic techniques. The band gap of nanocrystalline HfO2 was found to be 5.1 eV and the sample shows a broad PL emission at 628 nm. It is concluded that the transitions between intermediate energy levels in the band gap are responsible for the interesting photoluminescent properties of nanocrystalline HfO2.

  4. Measurement of Turbulence Modulation by Non-Spherical Particles

    DEFF Research Database (Denmark)

    Mandø, Matthias; Rosendahl, Lasse

    2010-01-01

    The change in the turbulence intensity of an air jet resulting from the addition of particles to the flow is measured using Laser Doppler Anemometry. Three distinct shapes are considered: the prolate spheroid, the disk and the sphere. Measurements of the carrier phase and particle phase velocities......, the particle mass flow and the integral length scale of the flow. The expression developed on basis of spherical particles only is applied on the data for the non-spherical particles. The results suggest that non-spherical particles attenuate the carrier phase turbulence significantly more than spherical...

  5. Stable tetragonal phase and magnetic properties of Fe-doped HfO2 nanoparticles

    Directory of Open Access Journals (Sweden)

    T. S. N. Sales

    2017-05-01

    Full Text Available In this paper, the effect in structural and magnetic properties of iron doping with concentration of 20% in hafnium dioxide (HfO2 nanoparticles is investigated. HfO2 is a wide band gap oxide with great potential to be used as high-permittivity gate dielectrics, which can be improved by doping. Nanoparticle samples were prepared by sol-gel chemical method and had their structure, morphology, and magnetic properties, respectively, investigated by X-ray diffraction (XRD, transmission electron microscopy (TEM and scanning electron microscopy (SEM with electron back scattering diffraction (EBSD, and magnetization measurements. TEM and SEM results show size distribution of particles in the range from 30 nm to 40 nm with small dispersion. Magnetization measurements show the blocking temperature at around 90 K with a strong paramagnetic contribution. XRD results show a major tetragonal phase (94%.

  6. Thermal stability of HfO2 nanotube arrays

    Energy Technology Data Exchange (ETDEWEB)

    Qiu, Xiaofeng [ORNL; Howe, Jane Y [ORNL; Meyer III, Harry M [ORNL; Tuncer, Enis [ORNL; Paranthaman, Mariappan Parans [ORNL

    2010-01-01

    Thermal stability of highly ordered hafnium oxide (HfO2) nanotube arrays prepared through an electrochemical anodization method in the presence of ammonium fluoride is investigated in a temperature range of room temperature to 900 C in flowing argon atmosphere. The formation of the HfO2 nanotube arrays was monitored by current density transient characteristics during anodization of hafnium metal foil. Morphologies of the as-grown and post-annealed HfO2 nanotube arrays were analyzed by powder Xray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Although monoclinic HfO2 is thermally stable up to 2000K in bulk, the morphology of HfO2 nanotube arrays degraded at 900 C. A detailed X-ray photoelectron spectroscopy (XPS) study revealed that the thermal treatment significantly impacted the composition and the chemical environment of the core elements (Hf and O), as well as F content coming from the electrolyte. Possible reasons for the degradation of the nanotube at high temperature were discussed based on XPS study and possible future improvements have also been suggested. Moreover, dielectric measurements were carried out on both the as-grown amorphous film and 500 C post-annealed crystalline film. This study will help us to understand the temperature impact on the morphology of nanotube arrays, which is important to its further applications at elevated temperatures.

  7. Energetic particles in spherical tokamak plasmas

    Science.gov (United States)

    McClements, K. G.; Fredrickson, E. D.

    2017-05-01

    Spherical tokamaks (STs) typically have lower magnetic fields than conventional tokamaks, but similar mass densities. Suprathermal ions with relatively modest energies, in particular beam-injected ions, consequently have speeds close to or exceeding the Alfvén velocity, and can therefore excite a range of Alfvénic instabilities which could be driven by (and affect the behaviour of) fusion α-particles in a burning plasma. STs heated with neutral beams, including the small tight aspect ratio tokamak (START), the mega amp spherical tokamak (MAST), the national spherical torus experiment (NSTX) and Globus-M, have thus provided an opportunity to study toroidal Alfvén eigenmodes (TAEs), together with higher frequency global Alfvén eigenmodes (GAEs) and compressional Alfvén eigenmodes (CAEs), which could affect beam current drive and channel fast ion energy into bulk ions in future devices. In NSTX GAEs were correlated with a degradation of core electron energy confinement. In MAST pulses with reduced magnetic field, CAEs were excited across a wide range of frequencies, extending to the ion cyclotron range, but were suppressed when hydrogen was introduced to the deuterium plasma, apparently due to mode conversion at ion-ion hybrid resonances. At lower frequencies fishbone instabilities caused fast particle redistribution in some MAST and NSTX pulses, but this could be avoided by moving the neutral beam line away from the magnetic axis or by operating the plasma at either high density or elevated safety factor. Fast ion redistribution has been observed during GAE avalanches on NSTX, while in both NSTX and MAST fast ions were transported by saturated kink modes, sawtooth crashes, resonant magnetic perturbations and TAEs. The energy dependence of fast ion redistribution due to both sawteeth and TAEs has been studied in Globus-M. High energy charged fusion products are unconfined in present-day STs, but have been shown in MAST to provide a useful diagnostic of beam ion

  8. Friction factor for water flow through packed beds of spherical and non-spherical particles

    Directory of Open Access Journals (Sweden)

    Kaluđerović-Radoičić Tatjana

    2017-01-01

    Full Text Available The aim of this work was the experimental evaluation of different friction factor correlations for water flow through packed beds of spherical and non-spherical particles at ambient temperature. The experiments were performed by measuring the pressure drop across the bed. Packed beds made of monosized glass spherical particles of seven different diameters were used, as well as beds made of 16 fractions of quartz filtration sand obtained by sieving (polydisperse non-spherical particles. The range of bed voidages was 0.359–0.486, while the range of bed particle Reynolds numbers was from 0.3 to 286 for spherical particles and from 0.1 to 50 for non-spherical particles. The obtained results were compared using a number of available literature correlations. In order to improve the correlation results for spherical particles, a new simple equation was proposed in the form of Ergun’s equation, with modified coefficients. The new correlation had a mean absolute deviation between experimental and calculated values of pressure drop of 9.04%. For non-spherical quartz filtration sand particles the best fit was obtained using Ergun’s equation, with a mean absolute deviation of 10.36%. Surface-volume diameter (dSV necessary for correlating the data for filtration sand particles was calculated based on correlations for dV = f(dm and Ψ = f(dm. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. ON172022

  9. Properties of HfO2 and HfO2: Y films grown by atomic layer deposition in an advanced monocyclopentadienyl-based process

    Science.gov (United States)

    Tamm, A.; Kukli, K.; Niinistö, J.; Lu, J.; Ritala, M.; Leskelä, M.

    2010-02-01

    Uniform HfO2 and HfO2:Y (7-8 cat.% Y) thin films were grown from a novel cyclopentadienyl-alkylamido precursor CpHf(NMe2)3, (CpMe)3Y and O3 at 300 °C. HfO2:Y films possessed somewhat higher roughness, and crystallized upon annealing at 500 °C in the form of cubic or tetragonal polymorph, compared to monoclinic HfO2 films. HfO2:Y demonstrated lower capacitance equivalent oxide thickness compared to HfO2, although HfO2films occurred slightly better insulating. Higher capacitance required intense crystallization achieved in the films grown to thicknesses exceeding 6 nm.

  10. Synthesis of freestanding HfO2 nanostructures

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    Boyle Kayla

    2011-01-01

    Full Text Available Abstract Two new methods for synthesizing nanostructured HfO2 have been developed. The first method entails exposing HfTe2 powders to air. This simple process resulted in the formation of nanometer scale crystallites of HfO2. The second method involved a two-step heating process by which macroscopic, freestanding nanosheets of HfO2 were formed as a byproduct during the synthesis of HfTe2. These highly two-dimensional sheets had side lengths measuring up to several millimeters and were stable enough to be manipulated with tweezers and other instruments. The thickness of the sheets ranged from a few to a few hundred nanometers. The thinnest sheets appeared transparent when viewed in a scanning electron microscope. It was found that the presence of Mn enhanced the formation of HfO2 by exposure to ambient conditions and was necessary for the formation of the large scale nanosheets. These results present new routes to create freestanding nanostructured hafnium dioxide. PACS: 81.07.-b, 61.46.Hk, 68.37.Hk.

  11. Fluorescence of molecules placed near a spherical particle: Rabi splitting

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    M.M. Dvoynenko

    2017-12-01

    Full Text Available Theoretical study of spontaneously emitted spectra of point-like source placed near spherical Ag particle was performed. It was shown that near-field electromagnetic interaction between a point-like emitter and spherical Ag particle leads to strong coupling between them at very small emitter-metal surface distances. It was shown that values of Rabi splitting are quantitatively close to that of emitter-flat substrate interaction.

  12. Turbulence Modulation by Non-Spherical Particles

    DEFF Research Database (Denmark)

    Mandø, Matthias

    This study deals with the interaction between turbulence and non-spherical particles and represents an extension of the modeling framework for particleladen flows. The effect of turbulence on particles is commonly referred to as turbulent dispersion while the effect of particles on the carrier...... phase turbulence is known as turbulence modulation. Whereas the former is well understood, no commonly accepted explanation has been presented for the latter. Moreover, considerations regarding the influence of shape on the experienced turbulence modulation must be considered as terra incognita......-spherical particles and turbulence modulation are outlined. A complete description of the motion of non-spherical particles is still lacking. However, evidence suggests that the equation of motion for a sphere only represent an asymptotical value for a more general, but yet unformulated, description of the motion...

  13. Preparation of spherical particles by vibrating orifice technique

    Science.gov (United States)

    Shibata, Shuichi; Tomizawa, Atsushi; Yoshikawa, Hidemi; Yano, Tetsuji; Yamane, Masayuki

    2000-05-01

    Preparation of micrometer-sized spherical particles containing Rhodamine 6G (R6G) has been investigated for the spherical cavity micro-laser. Using phenyl triethoxy silane (PTES) as a starting material, R6G-doped monodisperse spherical particles were prepared by the vibrating orifice technique. Processing consists of two major processes: (1) Hydrolysis and polymerization of PTES and (2) Droplet formation from PTES oligomers by vibrating orifice technique. A cylindrical liquid jet passing through the orifice of 10 and 20 micrometers in diameter breaks up into equal- sized droplets by mechanical vibration. Alcohol solvent of these droplets was evaporated during flying with carrier gas and subsequently solidified in ammonium water trap. For making smooth surface and god shaped particles, control of molecular weight of PTES oligomer was essential. R6G-doped hybrid spherical particles of 4 to 10 micrometers size of cavity structure were successfully obtained. The spherical particles were pumped by a second harmonic pulse of Q- switched Nd:YAG laser and laser emission peaks were observed at wavelengths which correspond to the resonance modes.

  14. Study of Direct-Contact HfO2/Si Interfaces

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    Noriyuki Miyata

    2012-03-01

    Full Text Available Controlling monolayer Si oxide at the HfO2/Si interface is a challenging issue in scaling the equivalent oxide thickness of HfO2/Si gate stack structures. A concept that the author proposes to control the Si oxide interface by using ultra-high vacuum electron-beam HfO2 deposition is described in this review paper, which enables the so-called direct-contact HfO2/Si structures to be prepared. The electrical characteristics of the HfO2/Si metal-oxide-semiconductor capacitors are reviewed, which suggest a sufficiently low interface state density for the operation of metal-oxide-semiconductor field-effect-transistors (MOSFETs but reveal the formation of an unexpected strong interface dipole. Kelvin probe measurements of the HfO2/Si structures provide obvious evidence for the formation of dipoles at the HfO2/Si interfaces. The author proposes that one-monolayer Si-O bonds at the HfO2/Si interface naturally lead to a large potential difference, mainly due to the large dielectric constant of the HfO2. Dipole scattering is demonstrated to not be a major concern in the channel mobility of MOSFETs.

  15. DLVO interaction energies between hollow spherical particles and collector surfaces

    Science.gov (United States)

    The surface element integration technique was used to systematically study Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energies/forces between hollow spherical particles (HPs) and a planar surface or two intercepting half planes under different ionic strength conditions. The inner and outer ...

  16. Calculation of the electrophoretic mobility of a spherical colloid particle

    NARCIS (Netherlands)

    Wiersema, P.H.; Loeb, A.L.; Overbeek, J.Th.G.

    A new calculation of the relation between the electrophoretic mobility and the ζ-potential of a spherical colloid particle is presented. The model consists of a rigid, electrically insulating sphere surrounded by a Gouy-Chapman double layer. The appropriate differential equations (which account for

  17. Dye-doped spherical particles of optical cavity structure

    Science.gov (United States)

    Shibata, Shuichi; Yano, Tetsuji; Yamane, Masayuki

    1997-10-01

    Preparation of micrometer-sized spherical particles containing Rhodamine 6G (R6G) has been investigated for spherical cavity structure. Hydrolysis and polymerization processes of phenyltriethoxysilane (PTES) as a starting material was pursued by observing the change of PTES/R6G in HCl solution with its optical absorption and viscosity. As the polymerization of PTES proceeded, increase of molecular size resulted in change its properties from hydrophilic to hydrophobic, and subsequently the solution separated into two layers of aqueous and organic. Polymerized PTES in the organic layer showed good affinity with incorporated R6G, and high monomer/dimer ratio in particles was achieved. Moreover, using them intermixing of unsuitable particles of submicron size was avoided, because hydrolyzed PTES of small molecular size that is the origin of submicron-sized particles was removed to the aqueous layer. With stirring, titration of diluted droplets containing polymerized PTES was suitable for preparing several micrometer sized particles, and followed by solidification in ammonia water. Degree of the polymerization of PTES and viscosity of liquid droplets were the key factors for determining the properties of R6G-doped spherical particles of optical cavity structure.

  18. Orientation statistics of non-spherical particles sedimenting in turbulence

    Science.gov (United States)

    Kramel, Stefan; Tierney, Lydia; Rees, Wyatt; Voth, Greg A.; Menon, Udayshankar; Roy, Anubhab; Koch, Donald L.

    2016-11-01

    We study the sedimentation of non-spherical particles in turbulence. The particle orientation is determined by a competition between inertial torques causing a preferential alignment and turbulence randomizing the orientation. The relative importance is quantified by a settling number SF defined as the ratio of the tumbling-rate from inertial torques and from turbulence. The experiments focus on the orientation statistics of particles formed from several slender arms, including fibers and particles with three arms in planar symmetry (triads), which allows us to study alignment of both fibers and disk-like particles. We measure the time-resolved 3D orientations of the particles along with the fluid velocity field around them in a vertical water tunnel. An active jet array with 40 individually controllable jets enables us to adjust the turbulence intensity and observe the transition from strongly aligned particles to randomized orientations as SF is decreased. Results are compared to simulations and theory based on slender body theory.

  19. Strongly Localized Image States of Spherical Graphitic Particles

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    Godfrey Gumbs

    2014-01-01

    Full Text Available We investigate the localization of charged particles by the image potential of spherical shells, such as fullerene buckyballs. These spherical image states exist within surface potentials formed by the competition between the attractive image potential and the repulsive centripetal force arising from the angular motion. The image potential has a power law rather than a logarithmic behavior. This leads to fundamental differences in the nature of the effective potential for the two geometries. Our calculations have shown that the captured charge is more strongly localized closest to the surface for fullerenes than for cylindrical nanotube.

  20. Ultrasmooth, Highly Spherical Monocrystalline Gold Particles for Precision Plasmonics

    KAUST Repository

    Lee, You-Jin

    2013-12-23

    Ultrasmooth, highly spherical monocrystalline gold particles were prepared by a cyclic process of slow growth followed by slow chemical etching, which selectively removes edges and vertices. The etching process effectively makes the surface tension isotropic, so that spheres are favored under quasi-static conditions. It is scalable up to particle sizes of 200 nm or more. The resulting spherical crystals display uniform scattering spectra and consistent optical coupling at small separations, even showing Fano-like resonances in small clusters. The high monodispersity of the particles we demonstrate should facilitate the self-assembly of nanoparticle clusters with uniform optical resonances, which could in turn be used to fabricate optical metafluids. Narrow size distributions are required to control not only the spectral features but also the morphology and yield of clusters in certain assembly schemes. © 2013 American Chemical Society.

  1. Rheotaxis of spherical active particles near a planar wall.

    Science.gov (United States)

    Uspal, W E; Popescu, M N; Dietrich, S; Tasinkevych, M

    2015-09-07

    For active particles the interplay between the self-generated hydrodynamic flow and an external shear flow, especially near bounding surfaces, can result in a rich behavior of the particles not easily foreseen from the consideration of the active and external driving mechanisms in isolation. For instance, under certain conditions, the particles exhibit "rheotaxis", i.e., they align their direction of motion with the plane of shear spanned by the direction of the flow and the normal of the bounding surface and move with or against the flow. To date, studies of rheotaxis have focused on elongated particles (e.g., spermatozoa), for which rheotaxis can be understood intuitively in terms of a "weather vane" mechanism. Here we investigate the possibility that spherical active particles, for which the "weather vane" mechanism is excluded due to the symmetry of the shape, may nevertheless exhibit rheotaxis. Combining analytical and numerical calculations, we show that, for a broad class of spherical active particles, rheotactic behavior may emerge via a mechanism which involves "self-trapping" near a hard wall owing to the active propulsion of the particles, combined with their rotation, alignment, and "locking" of the direction of motion into the shear plane. In this state, the particles move solely up- or downstream at a steady height and orientation.

  2. Hierarchical structures of ZnO spherical particles synthesized solvothermally

    Directory of Open Access Journals (Sweden)

    Noriko Saito and Hajime Haneda

    2011-01-01

    Full Text Available We review the solvothermal synthesis, using a mixture of ethylene glycol (EG and water as the solvent, of zinc oxide (ZnO particles having spherical and flower-like shapes and hierarchical nanostructures. The preparation conditions of the ZnO particles and the microscopic characterization of the morphology are summarized. We found the following three effects of the ratio of EG to water on the formation of hierarchical structures: (i EG restricts the growth of ZnO microcrystals, (ii EG promotes the self-assembly of small crystallites into spheroidal particles and (iii the high water content of EG results in hollow spheres.

  3. Energetic particle acceleration in spherically symmetric accretion flows and shocks

    Science.gov (United States)

    Webb, G. M.; Bogdan, T. J.

    1987-01-01

    Steady state, spherically symmetric solutions of the cosmic-ray transport equation describing the acceleration of energetic particles in galactic accretion flows onto neutron stars, black holes, white dwarfs, and protostars are studied. The results indicate that astrophysical accretion flows can be partitioned into distinct classes depending upon whether the accretion rate lies above or below a critical value of a few times 10 to the -7th stellar masses/yr. When the particle transport is convection-dominated, both classes of accretion flows exhibit a spectral index appropriate for first-order Fermi acceleration at a plane shock in the absence of losses. As the particle transport becomes diffusion-dominated, both classes show a break and precipitous falloff in the particle spectrum due to the escape of these particles from the accretion flow. The precise nature of the spectrum depends on the relationship between the particle momentum and the spatial diffusion coefficient.

  4. Rigid spherical particles in highly turbulent Taylor-Couette flow

    Science.gov (United States)

    Bakhuis, Dennis; Verschoof, Ruben A.; Mathai, Varghese; Huisman, Sander G.; Lohse, Detlef; Sun, Chao

    2016-11-01

    Many industrial and maritime processes are subject to enormous frictional losses. Reducing these losses even slightly will already lead to large financial and environmental benefits. The understanding of the underlying physical mechanism of frictional drag reduction is still limited, for example, in bubbly drag reduction there is an ongoing debate whether deformability and bubble size are the key parameters. In this experimental study we report high precision torque measurements using rigid non-deformable spherical particles in highly turbulent Taylor-Couette flow with Reynolds numbers up to 2 ×106 . The particles are made of polystyrene with an average density of 1.036 g cm-3 and three different diameters: 8mm, 4mm, and 1.5mm. Particle volume fractions of up to 6% were used. By varying the particle diameter, density ratio of the particles and the working fluid, and volume fraction of the particles, the effect on the torque is compared to the single phase case. These systematic measurements show that adding rigid spherical particles only results in very minor drag reduction. This work is financially supported by Netherlands Organisation for Scientific Research (NWO) by VIDI Grant Number 13477.

  5. Kinetic pathway of the ferroelectric phase formation in doped HfO2 films

    Science.gov (United States)

    Xu, Lun; Nishimura, Tomonori; Shibayama, Shigehisa; Yajima, Takeaki; Migita, Shinji; Toriumi, Akira

    2017-09-01

    The dopant-induced ferroelectric HfO2 formation has been systematically investigated by using cation (Sc, Y, Nb, Al, Si, Ge, and Zr) and anion (N) dopants. Both differences and similarities are discussed among various dopants by focusing on two major factors, the oxygen vacancy (Vo) and the dopant ionic size. First, the doping concentration dependence of the remanent polarization in 27 (±2) nm HfO2 films is quantitatively estimated. Then, by comparing the polarization result with the structural transformation in doped HfO2, the pathway of the dopant-induced HfO2 phase transition is discussed among monoclinic, ferroelectric orthorhombic, tetragonal, and cubic phases. Finally, it is addressed that a dopant species independent phase transition route may exist in HfO2 owing to the same kinetic transition process, in which the ferroelectric phase seems to be at an intermediate state between tetragonal and monoclinic phases.

  6. Particle digital in-line holography with spherical wave recording

    Science.gov (United States)

    Ge, Baozhen; Lu, Qieni; Zhang, Yimo

    2003-09-01

    In this paper, we propose a method of digital in-line holography of particle. A diverging spherical beam is used for illumination in recording hologram, the complex amplitude distribution generated by particle field at a single plane located in the Fresnel diffraction region is recorded by CCD, and a plane beam for reconstructing hologram, then, the magnified image can be obtained by numerical reconstruction in computer. This procedure can be interpreted by Fourier optical theory and the theoretical analysis have been done in detail, the experimental results, the air freshener being subject, are also given.

  7. Magnetic-luminescent spherical particles synthesized by ultrasonic spray pyrolysis

    Science.gov (United States)

    Michel, Norma L.; Flores, Dora L.; Hirata, Gustavo A.

    2015-07-01

    The combination of magnetic and luminescent properties in a single particle system, opens-up a wide range of potential applications in biotechnology and biomedicine. In this work, we performed the synthesis of magnetic-luminescent Gd2O3:Eu3+@Fe2O3 particles by ultrasonic spray pyrolysis performed in a tubular furnace. In order to achieve the composite formation, commercial superparamagnetic Fe3O4 nanoparticles were coated with a luminescent Eu3+-doped Gd2O3 shell in a low-cost one-step process. The spray pyrolysis method yields deagglomerated spherical shape magneto/luminescent particles. The photoluminescence spectra under UV excitation (λExc = 265 nm) of the magnetic Gd2O3:Eu3+@Fe2O3 compound showed the characteristic red emission of Eu3+ (λEm = 612 nm). This magneto/luminescent system will find applications in biomedicine and biotechnology.

  8. Spherical particle sedimenting in weakly viscoelastic shear flow

    Science.gov (United States)

    Einarsson, Jonas; Mehlig, Bernhard

    2017-06-01

    We consider the dynamics of a small spherical particle driven through an unbounded viscoelastic shear flow by an external force. We give analytical solutions to both the mobility problem (the velocity of a forced particle) and the resistance problem (the force on a fixed particle), valid to second order in the dimensionless Deborah and Weissenberg numbers, which represent the elastic relaxation time of the fluid relative to the rate of translation and the imposed shear rate. We find a shear-induced lift at O (Wi ) , a modified drag at O (De2) and O (Wi2) , and a second lift that is orthogonal to the first, at O (Wi2) . The relative importance of these effects depends strongly on the orientation of the forcing relative to the shear. We discuss how these forces affect the terminal settling velocity in an inclined shear flow. We also describe a basis set of symmetric Cartesian tensors and demonstrate how they enable general tensorial perturbation calculations such as the present theory. In particular, this scheme allows us to write down a solution to the inhomogeneous Stokes equations, required by the perturbation expansion, by a sequence of algebraic manipulations well suited to computer implementation.

  9. Direct Simulation of Extinction in a Slab of Spherical Particles

    Science.gov (United States)

    Mackowski, D.W.; Mishchenko, Michael I.

    2013-01-01

    The exact multiple sphere superposition method is used to calculate the coherent and incoherent contributions to the ensemble-averaged electric field amplitude and Poynting vector in systems of randomly positioned nonabsorbing spherical particles. The target systems consist of cylindrical volumes, with radius several times larger than length, containing spheres with positional configurations generated by a Monte Carlo sampling method. Spatially dependent values for coherent electric field amplitude, coherent energy flux, and diffuse energy flux, are calculated by averaging of exact local field and flux values over multiple configurations and over spatially independent directions for fixed target geometry, sphere properties, and sphere volume fraction. Our results reveal exponential attenuation of the coherent field and the coherent energy flux inside the particulate layer and thereby further corroborate the general methodology of the microphysical radiative transfer theory. An effective medium model based on plane wave transmission and reflection by a plane layer is used to model the dependence of the coherent electric field on particle packing density. The effective attenuation coefficient of the random medium, computed from the direct simulations, is found to agree closely with effective medium theories and with measurements. In addition, the simulation results reveal the presence of a counter-propagating component to the coherent field, which arises due to the internal reflection of the main coherent field component by the target boundary. The characteristics of the diffuse flux are compared to, and found to be consistent with, a model based on the diffusion approximation of the radiative transfer theory.

  10. Small intestinal transit of spherical particles in the active rat

    Energy Technology Data Exchange (ETDEWEB)

    Beall, P.T.; Sutton, S.C.; LeRoy-Wayne, S.

    1986-03-05

    Reproducible measurements of small intestine transit for spherical particles of 0.5 ..mu.. to 1 mm diameter, have been accomplished in the conscious rat. A short cannula of polyethylene is surgically implanted into the duodenum and exists through the abdominal wall. After recovery, a bolus of saline containing colored or isotopically labeled particulate material and an internal standard of NaCr/sup 51/O/sub 4/ is introduced with a modified pipette tip that snugly fills the cannula to prevent back flow. The rats eat and drink during the transit period and are maintained on a reversed light cycle so that transit is measured during their physically active period. Glass microspheres of 1mm, 500 ..mu.., and 50 ..mu.. were followed at 30 min, 1 hr, and 2 hr intervals by opening the intestine and photographing 1 cm segments along its length. Polymer beads of 500 ..mu.., 125 ..mu.., and 70 ..mu.. were labeled with /sup 125/I and located by freezing the exteriorized intestine and counting 1 cm segments in a gamma counter. Movement of the fluid bolus as detected by NaCr/sup 51/O/sub 4/ was reproducible with the fluid front moving through 59%, 73%, and 81% of the length at 30 min, 1 hr, and 2 hr. One millimeter to 125 ..mu.. glass and polymer beads moved with the fluid bolus. Evidence for separation of the fluid phase and particles under approx. 100 ..mu.. is accumulating. It is hypothesized that small particles under a critical size may become lodged in the mucus lining of the intestinal wall.

  11. Conduction Mechanism and Improved Endurance in HfO2-Based RRAM with Nitridation Treatment

    Science.gov (United States)

    Yuan, Fang-Yuan; Deng, Ning; Shih, Chih-Cheng; Tseng, Yi-Ting; Chang, Ting-Chang; Chang, Kuan-Chang; Wang, Ming-Hui; Chen, Wen-Chung; Zheng, Hao-Xuan; Wu, Huaqiang; Qian, He; Sze, Simon M.

    2017-10-01

    A nitridation treatment technology with a urea/ammonia complex nitrogen source improved resistive switching property in HfO2-based resistive random access memory (RRAM). The nitridation treatment produced a high performance and reliable device which results in superior endurance (more than 109 cycles) and a self-compliance effect. Thus, the current conduction mechanism changed due to defect passivation by nitrogen atoms in the HfO2 thin film. At a high resistance state (HRS), it transferred to Schottky emission from Poole-Frenkel in HfO2-based RRAM. At low resistance state (LRS), the current conduction mechanism was space charge limited current (SCLC) after the nitridation treatment, which suggests that the nitrogen atoms form Hf-N-Ox vacancy clusters (Vo +) which limit electron movement through the switching layer.

  12. Optical characterization of polar HfO2 nanoparticles in the mid- and far-infrared

    Science.gov (United States)

    Dominguez, O.; McGinnity, T. L.; Roeder, R. K.; Hoffman, A. J.

    2017-07-01

    Monoclinic HfO2 nanoparticles with nominal diameters of 9, 30, and 45 nm are characterized using transmission and reflection spectroscopy from the mid- to far-infrared. Phonon modes are identified in the measured spectra and agree with previously reported values in HfO2 thin films and density functional perturbation theory calculations. An anomaly in both reflection and transmission is observed at 556 cm-1 that is not attributed to the optical phonon modes. Numerical models predict a localized surface phonon polariton mode near this frequency, and we attribute the anomaly to coupling to this surface mode. The results of this work suggest that HfO2 nanoparticles could enable engineered optical properties in new mid- and far-infrared materials and devices.

  13. The use of rotating electric are for spherical particle production

    Directory of Open Access Journals (Sweden)

    Bica, Ion

    2000-08-01

    Full Text Available This work presents an experimental device designed to obtain spherical partióles by means of a rotating electric are. A rotation frequency of the electric are of 750 s-1, a voltage of 50 V (dc and a current of 100 A was used. The mass flow rate was 3 g.min-1. Under these conditions particles of 15 to 20 μm in diameter were obtained.

    Este trabajo presenta la instalación experimental destinada a la obtención de partículas esféricas utilizando un arco eléctrico rotatorio. Para ello se utilizó una frecuencia de rotación del arco eléctrico de 750 s-1 a un voltaje del arco de 50 V (cc y una corriente de 100 A. La velocidad de flujo de materia fue de 3 g.min-1 obteniéndose partículas de diámetros comprendidos entre 15 y 20 μm.

  14. RAPID OPTIMAL SPH PARTICLE DISTRIBUTIONS IN SPHERICAL GEOMETRIES FOR CREATING ASTROPHYSICAL INITIAL CONDITIONS

    Energy Technology Data Exchange (ETDEWEB)

    Raskin, Cody; Owen, J. Michael [Lawrence Livermore National Laboratory, P.O. Box 808, L-038, Livermore, CA 94550 (United States)

    2016-04-01

    Creating spherical initial conditions in smoothed particle hydrodynamics simulations that are spherically conformal is a difficult task. Here, we describe two algorithmic methods for evenly distributing points on surfaces that when paired can be used to build three-dimensional spherical objects with optimal equipartition of volume between particles, commensurate with an arbitrary radial density function. We demonstrate the efficacy of our method against stretched lattice arrangements on the metrics of hydrodynamic stability, spherical conformity, and the harmonic power distribution of gravitational settling oscillations. We further demonstrate how our method is highly optimized for simulating multi-material spheres, such as planets with core–mantle boundaries.

  15. A CFD-DEM study of single bubble formation in gas fluidization of spherical and non-spherical particles

    Directory of Open Access Journals (Sweden)

    Shrestha Siddhartha

    2017-01-01

    Full Text Available Bubble dynamics significantly affect the hydrodynamics of gas-solid fluidized bed since they influence the gas-solid mixing. In this study, simulations using CFD-DEM were carried out to characterize the bubble size and shape for a bubble formed at a single orifice in gas-solid fluidized bed. Impact of parameters such as jet velocity, orifice size and particle shape on bubble equivalent diameter and bubble aspect ratio were analysed and discussed. Bubble equivalent diameter was found to increase with increasing jet velocity, decreasing bed width to orifice width ratio, and particle shape deviating from spherical. The bubble shape illustrated by aspect ratio, was found to elongate more as it rise through the bed and then commence to expand horizontally after it was detached from the orifice. Aspect ratio was found to be closer to a circle for the bubble at higher jet velocity, lower orifice width to bed ratio and for non-spherical particles.

  16. A CFD-DEM study of single bubble formation in gas fluidization of spherical and non-spherical particles

    Science.gov (United States)

    Shrestha, Siddhartha; Zhou, Zongyan

    2017-06-01

    Bubble dynamics significantly affect the hydrodynamics of gas-solid fluidized bed since they influence the gas-solid mixing. In this study, simulations using CFD-DEM were carried out to characterize the bubble size and shape for a bubble formed at a single orifice in gas-solid fluidized bed. Impact of parameters such as jet velocity, orifice size and particle shape on bubble equivalent diameter and bubble aspect ratio were analysed and discussed. Bubble equivalent diameter was found to increase with increasing jet velocity, decreasing bed width to orifice width ratio, and particle shape deviating from spherical. The bubble shape illustrated by aspect ratio, was found to elongate more as it rise through the bed and then commence to expand horizontally after it was detached from the orifice. Aspect ratio was found to be closer to a circle for the bubble at higher jet velocity, lower orifice width to bed ratio and for non-spherical particles.

  17. The conduction bands of MgO, MgS and HfO2

    NARCIS (Netherlands)

    Boer, P.K. de; Groot, R.A. de

    1998-01-01

    Electronic structure calculations for MgO, MgS and HfO2 are reported. It is shown that the conduction bands of MgO and MgS have predominantly anion character, contrary to the common picture of the conduction band being derived from cation states. In transition metal oxides, unoccupied anion states

  18. Thermal Conductivity and Water Vapor Stability of Ceramic HfO2-Based Coating Materials

    Science.gov (United States)

    Zhu, Dong-Ming; Fox, Dennis S.; Bansal, Narottam P.; Miller, Robert A.

    2004-01-01

    HfO2-Y2O3 and La2Zr2O7 are candidate thermal/environmental barrier coating materials for gas turbine ceramic matrix composite (CMC) combustor liner applications because of their relatively low thermal conductivity and high temperature capability. In this paper, thermal conductivity and high temperature phase stability of plasma-sprayed coatings and/or hot-pressed HfO2-5mol%Y2O3, HfO2-15mol%Y2O3 and La2Zr2O7 were evaluated at temperatures up to 1700 C using a steady-state laser heat-flux technique. Sintering behavior of the plasma-sprayed coatings was determined by monitoring the thermal conductivity increases during a 20-hour test period at various temperatures. Durability and failure mechanisms of the HfO2-Y2O3 and La2Zr2O7 coatings on mullite/SiC Hexoloy or CMC substrates were investigated at 1650 C under thermal gradient cyclic conditions. Coating design and testing issues for the 1650 C thermal/environmental barrier coating applications will also be discussed.

  19. Nanomechanical study of amorphous and polycrystalline ALD HfO2 thin films

    Science.gov (United States)

    K. Tapily; J.E. Jakes; D. Gu; H. Baumgart; A.A. Elmustafa

    2011-01-01

    Thin films of hafnium oxide (HfO2) were deposited by atomic layer deposition (ALD). The structural properties of the deposited films were characterised by transmission electron microscopy (TEM) and X-ray diffraction (XRD). We investigated the effect of phase transformations induced by thermal treatments on the mechanical properties of ALD HfO

  20. Elongated dust particles growth in a spherical glow discharge in ethanol

    Science.gov (United States)

    Fedoseev, A. V.; Sukhinin, G. I.; Sakhapov, S. Z.; Zaikovskii, A. V.; Novopashin, S. A.

    2018-01-01

    The formation of elongated dust particles in a spherical dc glow discharge in ethanol was observed for the first time. Dust particles were formed in the process of coagulation of ethanol dissociation products in the plasma of gas discharge. During the process the particles were captured into clouds in the electric potential wells of strong striations of spherical discharge. The size and the shape of dust particles are easily detected by naked eye after the illumination of the laser sheet. The description of the experimental setup and conditions, the analysis of size, shape and composition of the particles, the explanation of spatial ordering and orientation of these particles are presented.

  1. Application of spherical harmonics analysis on LBS particles and LBS fragments

    Directory of Open Access Journals (Sweden)

    Zhao Budi

    2017-01-01

    Full Text Available This paper applies surface parameterization and spherical harmonics analysis to the characterization of particle shapes of Leighton Buzzard sand (LBS particles and LBS fragments obtained from X-ray micro-tomography (μCT. The rotation, transition and scale independent spherical coefficients were obtained. The relationship between spherical coefficients and shape parameters of form, roundness and compactness was investigated. The coefficients of degree one determine the principal dimensions of an ellipsoid, which has a similar aspect ratio with the original surface. The coefficients of higher degree characterise more details by increasing the percentage of higher and lower mean curvature on the reconstructed surface. As the spherical degree increases, the reconstructed surface tend to have lower particle roundness, sphericity and convexity, and higher aspect ratio.

  2. Spherical molecularly imprinted polymer particles : A promising tool for molecular recognition in capillary electrokinetic separations

    NARCIS (Netherlands)

    de Boer, T; Mol, R; de Zeeuw, RA; de Jong, GJ; Sherrington, DC; Cormack, PAG; Ensing, K

    Spherical molecularly imprinted polymer particles obtained via precipitation polymerization, were introduced as a pseudostationary phase in capillary electrophoresis (CE) to study molecular recognition. Analyses were performed via a partial filling technique using (+)-ephedrine-imprinted

  3. On the motion of non-spherical particles at high Reynolds number

    DEFF Research Database (Denmark)

    Mandø, Matthias; Rosendahl, Lasse

    2010-01-01

    This paper contains a critical review of available methodology for dealing with the motion of non-spherical particles at higher Reynolds numbers in the Eulerian- Lagrangian methodology for dispersed flow. First, an account of the various attempts to classify the various shapes and the efforts...... towards finding a universal shape parameter is given and the details regarding the significant secondary motion associated with non-spherical particles are outlined. Most investigations concerning large non-spherical particles to date have been focused on finding appropriate correlations of the drag...... coefficient for specific shapes either by parameter variation or by using shape parameters. Particular emphasis is here placed on showing the incapability of one-dimensional shape parameters to predict the multifaceted secondary motion associated with non-spherical particles. To properly predict secondary...

  4. Gravitational sedimentation of cloud of solid spherical particles at small Reynolds numbers

    Directory of Open Access Journals (Sweden)

    Arkhipov Vladimir

    2015-01-01

    Full Text Available The experimental results of study of gravitational sedimentation of highly-concentrated systems of solid spherical particles at small Reynolds numbers Re<1 are presented. Empirical equation for drag coefficient of the particle assembly has been obtained. The influence of initial particle concentration in the cloud on its dynamics and velocity has been analysed.

  5. Formation of Al2O3-HfO2 Eutectic EBC Film on Silicon Carbide Substrate

    Directory of Open Access Journals (Sweden)

    Kyosuke Seya

    2015-01-01

    Full Text Available The formation mechanism of Al2O3-HfO2 eutectic structure, the preparation method, and the formation mechanism of the eutectic EBC layer on the silicon carbide substrate are summarized. Al2O3-HfO2 eutectic EBC film is prepared by optical zone melting method on the silicon carbide substrate. At high temperature, a small amount of silicon carbide decomposed into silicon and carbon. The components of Al2O3 and HfO2 in molten phase also react with the free carbon. The Al2O3 phase reacts with free carbon and vapor species of AlO phase is formed. The composition of the molten phase becomes HfO2 rich from the eutectic composition. HfO2 phase also reacts with the free carbon and HfC phase is formed on the silicon carbide substrate; then a high density intermediate layer is formed. The adhesion between the intermediate layer and the substrate is excellent by an anchor effect. When the solidification process finished before all of HfO2 phase is reduced to HfC phase, HfC-HfO2 functionally graded layer is formed on the silicon carbide substrate and the Al2O3-HfO2 eutectic structure grows from the top of the intermediate layer.

  6. Hydrogen-dependent low frequency noise and its physical mechanism of HfO2 resistance change random access memory

    Science.gov (United States)

    Chen, Y. Q.; Liu, X.; Liu, Y.; Peng, C.; Fang, W. X.; En, Y. F.; Huang, Y.

    2017-12-01

    The effect of hydrogen on low frequency noise characteristics of HfO2 resistance change random access memories (RRAMs) was investigated in this paper. The experimental results show that HfO2 RRAMs after hydrogen treatment take on the better uniformity of switch characteristics and the conduction enhancement behavior. Furthermore, it was found that the low frequency noise characteristics of the HfO2 RRAMs was significantly impacted by the hydrogen treatment, and at three kinds of typical resistance states, the low frequency noises of the HfO2 RRAMs after hydrogen treatment are larger than those of the fresh HfO2 RRAMs. The mechanism could be attributed to H induced oxygen vacancies, which serve as the additional traps for conduction due to the trap-assisted tunneling process. This will result in more random trap/detrap processes in the conducting filament, which gives rise to the larger low frequency noise in the HfO2 RRAMs. The results of this study may be useful in the design and application of HfO2 RRAMs.

  7. High Purity Tungsten Spherical Particle Preparation From WC-Co Spent Hard Scrap

    Directory of Open Access Journals (Sweden)

    Han Chulwoong

    2015-06-01

    Full Text Available Tungsten carbide-cobalt hard metal scrap was recycled to obtain high purity spherical tungsten powder by a combined hydrometallurgy and physical metallurgy pathway. Selective leaching of tungsten element from hard metal scrap occurs at solid / liquid interface and therefore enlargement of effective surface area is advantageous. Linear oxidation behavior of Tungsten carbide-cobalt and the oxidized scrap is friable to be pulverized by milling process. In this regard, isothermally oxidized Tungsten carbide-cobalt hard metal scrap was mechanically broken into particles and then tungsten trioxide particle was recovered by hydrometallurgical method. Recovered tungsten trioxide was reduced to tungsten particle in a hydrogen environment. After that, tungsten particle was melted and solidified to make a spherical one by RF (Ratio Frequency thermal plasma process. Well spherical tungsten micro-particle was successfully obtained from spent scrap. In addition to the morphological change, thermal plasma process showed an advantage for the purification of feedstock particle.

  8. Investigation of Gas Solid Fluidized Bed Dynamics with Non-Spherical Particles

    Energy Technology Data Exchange (ETDEWEB)

    Choudhuri, Ahsan [Univ. of Texas, El Paso, TX (United States). Dept. of Mechanical Engineering

    2013-06-30

    One of the largest challenges for 21st century is to fulfill global energy demand while also reducing detrimental impacts of energy generation and use on the environment. Gasification is a promising technology to meet the requirement of reduced emissions without compromising performance. Coal gasification is not an incinerating process; rather than burning coal completely a partial combustion takes place in the presence of steam and limited amounts of oxygen. In this controlled environment, a chemical reaction takes place to produce a mixture of clean synthetic gas. Gas-solid fluidized bed is one such type of gasification technology. During gasification, the mixing behavior of solid (coal) and gas and their flow patterns can be very complicated to understand. Many attempts have taken place in laboratory scale to understand bed hydrodynamics with spherical particles though in actual applications with coal, the particles are non-spherical. This issue drove the documented attempt presented here to investigate fluidized bed behavior using different ranges of non-spherical particles, as well as spherical. For this investigation, various parameters are controlled that included particle size, bed height, bed diameter and particle shape. Particles ranged from 355 µm to 1180 µm, bed diameter varied from 2 cm to 7 cm, two fluidized beds with diameters of 3.4 cm and 12.4 cm, for the spherical and non-spherical shaped particles that were taken into consideration. Pressure drop was measured with increasing superficial gas velocity. The velocity required in order to start to fluidize the particle is called the minimum fluidization velocity, which is one of the most important parameters to design and optimize within a gas-solid fluidized bed. This minimum fluidization velocity was monitored during investigation while observing variables factors and their effect on this velocity. From our investigation, it has been found that minimum fluidization velocity is independent of bed

  9. Role of Al doping in the filament disruption in HfO2 resistance switches

    Science.gov (United States)

    Brivio, Stefano; Frascaroli, Jacopo; Spiga, Sabina

    2017-09-01

    Resistance switching devices, whose operation is driven by formation (SET) and dissolution (RESET) of conductive paths shorting and disconnecting the two metal electrodes, have recently received great attention and a deep general comprehension of their operation has been achieved. However, the link between switching characteristics and material properties is still quite weak. In particular, doping of the switching oxide layer has often been investigated only for looking at performance upgrade and rarely for a meticulous investigation of the switching mechanism. In this paper, the impact of Al doping of HfO2 devices on their switching operations, retention loss mechanisms and random telegraph noise traces is investigated. In addition, phenomenological modeling of the switching operation is performed for device employing both undoped and doped HfO2. We demonstrate that Al doping influences the filament disruption process during the RESET operation and, in particular, it contributes in preventing an efficient restoration of the oxide with respect to undoped devices.

  10. Design and Fabrication of Interdigital Nanocapacitors Coated with HfO2

    Directory of Open Access Journals (Sweden)

    Gabriel González

    2015-01-01

    Full Text Available In this article nickel interdigital capacitors were fabricated on top of silicon substrates. The capacitance of the interdigital capacitor was optimized by coating the electrodes with a 60 nm layer of HfO2. An analytical solution of the capacitance was compared to electromagnetic simulations using COMSOL and with experimental measurements. Results show that modeling interdigital capacitors using Finite Element Method software such as COMSOL is effective in the design and electrical characterization of these transducers.

  11. Growth and phase stabilization of HfO 2 thin films by ALD using novel precursors

    Science.gov (United States)

    Niinistö, Jaakko; Mäntymäki, Miia; Kukli, Kaupo; Costelle, Leila; Puukilainen, Esa; Ritala, Mikko; Leskelä, Markku

    2010-01-01

    HfO 2 thin films were grown at temperatures between 250 and 400 °C by atomic layer deposition using novel cyclopentadienyl-alkylamido precursors, namely CpHf(NMe 2) 3 and (CpMe)Hf(NMe 2) 3 (Cp, cyclopentadienyl=C 5H 5). Ozone was used as the oxygen source. The self-limiting growth mode was verified at 300 °C with a growth rate of 0.7-0.8 Å/cycle, depending on the precursor. Thermal decomposition started to have an effect on the growth mechanism at temperatures near 350 °C. As compared to the widely applied Hf(NEtMe) 4 precursor, these novel precursors with higher thermal stability resulted in HfO 2 films with lower impurity contents. The carbon and hydrogen contents below 0.5 and 1.0 at.%, respectively, were characterized for films deposited at 300 °C from both novel precursors. The 50-nm-thick HfO 2 films deposited at 300 °C or above were crystallized in mixture of monoclinic and cubic or tetragonal phases. Doping with low amounts of yttrium and subsequent annealing of 7-nm-thick film on TiN stabilized the preferred high-permittivity cubic or tetragonal phases, resulting in low capacitance equivalent thickness and leakage current density.

  12. MISR Dark Water aerosol retrievals: operational algorithm sensitivity to particle non-sphericity

    Directory of Open Access Journals (Sweden)

    O. V. Kalashnikova

    2013-08-01

    Full Text Available The aim of this study is to theoretically investigate the sensitivity of the Multi-angle Imaging SpectroRadiometer (MISR operational (version 22 Dark Water retrieval algorithm to aerosol non-sphericity over the global oceans under actual observing conditions, accounting for current algorithm assumptions. Non-spherical (dust aerosol models, which were introduced in version 16 of the MISR aerosol product, improved the quality and coverage of retrievals in dusty regions. Due to the sensitivity of the retrieval to the presence of non-spherical aerosols, the MISR aerosol product has been successfully used to track the location and evolution of mineral dust plumes from the Sahara across the Atlantic, for example. However, the MISR global non-spherical aerosol optical depth (AOD fraction product has been found to have several climatological artifacts superimposed on valid detections of mineral dust, including high non-spherical fraction in the Southern Ocean and seasonally variable bands of high non-sphericity. In this paper we introduce a formal approach to examine the ability of the operational MISR Dark Water algorithm to distinguish among various spherical and non-spherical particles as a function of the variable MISR viewing geometry. We demonstrate the following under the criteria currently implemented: (1 Dark Water retrieval sensitivity to particle non-sphericity decreases for AOD below about 0.1 primarily due to an unnecessarily large lower bound imposed on the uncertainty in MISR observations at low light levels, and improves when this lower bound is removed; (2 Dark Water retrievals are able to distinguish between the spherical and non-spherical particles currently used for all MISR viewing geometries when the AOD exceeds 0.1; (3 the sensitivity of the MISR retrievals to aerosol non-sphericity varies in a complex way that depends on the sampling of the scattering phase function and the contribution from multiple scattering; and (4 non-sphericity

  13. Retrieval of spherical particle size distribution with an improved Tikhonov iteration method

    OpenAIRE

    Tang Hong

    2012-01-01

    The problem of retrieval for spherical particle size distribution in the independent mode is studied, and an improved Tikhonov iteration method is proposed. In this method, the particle size distribution is retrieved from the light extinction data through the Phillips-Twomey method firstly in the independent mode, and then the obtained inversion results of the particle size distribution is used as the initial distribution and the final retrieved particle size distribution is obtained. S...

  14. Collision efficiencies of diffusing spherical particles: hydrodynamic, van der Waals and electrostatic forces

    OpenAIRE

    Valioulis, Iraklis A.; List, E. John

    1984-01-01

    A practical limitation of the application of Smoluchowski's classical estimate for the collisions probability of two diffusing spherical particles in Brownian motion is the non-consideration of interparticle forcves. For suspended particles in water such forces can arise from the disturbance the particle causes in the fluid (hydrodynamic forces), from the cloud of ions which surround an electrically charged particle (double layer forces) or they can be of molecular origin (van der Waals force...

  15. Cavitation inception by almost spherical solid particles in water

    DEFF Research Database (Denmark)

    Marschall, H.B.; Mørch, Knud Aage; Keller, A.P.

    2003-01-01

    The tensile strength of water increases when solid particles are filtered out, and it becomes greater the smaller the remaining particles are. Natural particles are of random shape, making parametric studies on the relationship between tensile strength and particle characteristics difficult. In t...... that cavitation nuclei are related to the fine scale surface structures observed on the balls, and in dependence of their global radii of curvature, critical cavities are developed. A model of this development is presented. ©2003 American Institute of Physics....

  16. Investigation of point defects in HfO2 using positron annihilation spectroscopy: internal electric fields impact

    Science.gov (United States)

    Alemany, M.; Chabli, A.; Oudot, E.; Pierre, F.; Desgardin, P.; Bertin, F.; Gros-Jean, M.; Barthe, M. F.

    2017-01-01

    In this work, we report on the PAS characterization of sintered HfO2 bulk ceramic and HfO2 layers deposited with various methods on a silicon substrate with a layer thickness ranging from 25 to 100 nm. PAS measurements are sensitive to the deposition process type and the post-deposition annealing. Chemical and structural characterisations have been performed on the same samples. The PAS results are discussed regarding to the material defects of the different layers. In addition, a built-in electrical field induced by charged defects located at the HfO2/Si interface as well as in the HfO2 layer must be taken into account in the PAS data fitting. Both non-contact internal electrical field measurements and internal electrical field simulations support the PAS finding.

  17. Preparation for Spherical particles of Praseodymium doped Perovskite Red Phosphor by Hydrothermal Reaction

    Science.gov (United States)

    Kosaka, T.; Matsuda, A.; Mizunuma, M.; Tanaka, Y.

    2017-02-01

    Spherical particles of 0.5mol%Pr3+-doped CaTiO3 were prepared by hydrothermal reaction on dissolved CaCl2, Pr(NO3)3, and ammonium citratoperoxotitanate (IV) complex precursor solution with molar ratio of Ti/CA=1:2 and calcination in ambient atmosphere. The obtained particle exhibited red photoluminescence at 610nm. It is found that several particles have hollow structure. It is required that further investigation is needed to clarify the formation mechanism of these spherical hollow paricles.

  18. Sheet-like assemblies of spherical particles with point-symmetrical patches.

    Science.gov (United States)

    Mani, Ethayaraja; Sanz, Eduardo; Roy, Soumyajit; Dijkstra, Marjolein; Groenewold, Jan; Kegel, Willem K

    2012-04-14

    We report a computational study on the spontaneous self-assembly of spherical particles into two-dimensional crystals. The experimental observation of such structures stabilized by spherical objects appeared paradoxical so far. We implement patchy interactions with the patches point-symmetrically (icosahedral and cubic) arranged on the surface of the particle. In these conditions, preference for self-assembly into sheet-like structures is observed. We explain our findings in terms of the inherent symmetry of the patches and the competition between binding energy and vibrational entropy. The simulation results explain why hollow spherical shells observed in some Keplerate-type polyoxometalates (POM) appear. Our results also provide an explanation for the experimentally observed layer-by-layer growth of apoferritin--a quasi-spherical protein.

  19. Newtonian wormholes with spherical symmetry and tidal forces on test particles

    CERN Document Server

    Luz, Paulo

    2015-01-01

    A spherically symmetric wormhole in Newtonian gravitation in curved space, enhanced with a connection between the mass density and the Ricci scalar, is presented. The wormhole, consisting of two connected asymptotically flat regions, inhabits a spherically symmetric curved space. The gravitational potential, gravitational field and the pressure that supports the fluid that permeates the Newtonian wormhole are computed. Particle dynamics and tidal effects in this geometry are studied. The possibility of having Newtonian black holes in this theory is sketched.

  20. Stimulated emission from spherical particles - thermal stability of PTES-derived hybrid materials -

    Science.gov (United States)

    Yano, Tetsuji; Kitajima, Takahiro; Araya, Akinori; Shibata, Shuichi

    2002-10-01

    The effects of heat treatment on the optical quality of organic-norganic hybrid spherical particles were investigated. The spherical particles with a diameter of 6μm were prepared via sol-gel process from phenyl-tetraethyl-silane(PTES) using the vibrating orifice technique, and they showed strong oscillation signals based on the spherical resonance mode with low power threshold of the incident CW-Ar+ laser. Against the heat treatment on the slide glass plate, there were some particles which remained their spherical shape after 400°C heating depending on the condition of sol preparation. The survived particles were also found to have high photo-stability that they were not damaged from the laser irradiation of 514.5nm Ar+ light with a power >120mW/particle, while as-prepared particles were bursted by the irradiation <20mW/particles. From the measurements of micro Raman scattering spectroscopy, optical and secondary electron microscope and thermal analysis, the thermal stability of hybrid materials was considered.

  1. Density-conserving shape factors for particle simulations in cylindrical and spherical coordinates

    Science.gov (United States)

    Ruyten, Wilhelmus M.

    1993-01-01

    It is established that a particle-to-grid weighting which is based on both conventional particle-in-cell (PIC) and cloud-in-cell (CIC) shape factors will yield nonuniform grid densities, even in the case of uniform particle distributions, in both cylindrical and spherical coordinates. In view of this, alternative density-conserving weighting schemes are discussed which encompass modified PIC and CIC weighting. These alternative shape factors are mathematically no more complicated than the conventional nondensity-conserving expressions.

  2. A kinetic model for heterogeneous condensation of vapor on an insoluble spherical particle.

    Science.gov (United States)

    Luo, Xisheng; Fan, Yu; Qin, Fenghua; Gui, Huaqiao; Liu, Jianguo

    2014-01-14

    A kinetic model is developed to describe the heterogeneous condensation of vapor on an insoluble spherical particle. This new model considers two mechanisms of cluster growth: direct addition of water molecules from the vapor and surface diffusion of adsorbed water molecules on the particle. The effect of line tension is also included in the model. For the first time, the exact expression of evaporation coefficient is derived for heterogeneous condensation of vapor on an insoluble spherical particle by using the detailed balance. The obtained expression of evaporation coefficient is proved to be also correct in the homogeneous condensation and the heterogeneous condensation on a planar solid surface. The contributions of the two mechanisms to heterogeneous condensation including the effect of line tension are evaluated and analysed. It is found that the cluster growth via surface diffusion of adsorbed water molecules on the particle is more important than the direct addition from the vapor. As an example of our model applications, the growth rate of the cap shaped droplet on the insoluble spherical particle is derived. Our evaluation shows that the growth rate of droplet in heterogeneous condensation is larger than that in homogeneous condensation. These results indicate that an explicit kinetic model is benefit to the study of heterogeneous condensation on an insoluble spherical particle.

  3. Spherical Harmonic Analysis of Particle Velocity Distribution Function: Comparison of Moments and Anisotropies using Cluster Data

    Science.gov (United States)

    Gurgiolo, Chris; Vinas, Adolfo F.

    2009-01-01

    This paper presents a spherical harmonic analysis of the plasma velocity distribution function using high-angular, energy, and time resolution Cluster data obtained from the PEACE spectrometer instrument to demonstrate how this analysis models the particle distribution function and its moments and anisotropies. The results show that spherical harmonic analysis produced a robust physical representation model of the velocity distribution function, resolving the main features of the measured distributions. From the spherical harmonic analysis, a minimum set of nine spectral coefficients was obtained from which the moment (up to the heat flux), anisotropy, and asymmetry calculations of the velocity distribution function were obtained. The spherical harmonic method provides a potentially effective "compression" technique that can be easily carried out onboard a spacecraft to determine the moments and anisotropies of the particle velocity distribution function for any species. These calculations were implemented using three different approaches, namely, the standard traditional integration, the spherical harmonic (SPH) spectral coefficients integration, and the singular value decomposition (SVD) on the spherical harmonic methods. A comparison among the various methods shows that both SPH and SVD approaches provide remarkable agreement with the standard moment integration method.

  4. Hydrogen doping in HfO2 resistance change random access memory

    Science.gov (United States)

    Duncan, D.; Magyari-Köpe, B.; Nishi, Y.

    2016-01-01

    The structures and energies of hydrogen-doped monoclinic hafnium dioxide were calculated using density-functional theory. The electronic interactions are described within the LDA + U formalism, where on-site Coulomb corrections are applied to the 5d orbital electrons of Hf atoms and 2p orbital electrons of the O atoms. The effects of charge state, defect-defect interactions, and hydrogenation are investigated and compared with experiment. It is found that hydrogenation of HfO2 resistance-change random access memory devices energetically stabilizes the formation of oxygen vacancies and conductive vacancy filaments through multiple mechanisms, leading to improved switching characteristic and device yield.

  5. HfO 2 -based ferroelectric modulator of terahertz waves with graphene metamaterial

    Science.gov (United States)

    Jiang, Ran; Wu, Zheng-Ran; Han, Zu-Yin; Jung, Hyung-Suk

    2016-10-01

    Tunable modulations of terahertz waves in a graphene/ferroelectric-layer/silicon hybrid structure are demonstrated at low bias voltages. The modulation is due to the creation/elimination of an extra barrier in Si layer in response to the polarization in the ferroelectric Si:HfO2 layer. Considering the good compatibility of HfO2 with the Si-based semiconductor process, the highly tunable characteristics of the graphene metamaterial device under ferroelectric effect open up new avenues for graphene-based high performance integrated active photonic devices compatible with the silicon technology. Project supported by the National Natural Science Foundation of China (Grant No. 11374182).

  6. Fabrication and Application of Mono-sized Spherical Micro Particles by Pulsated Orifice Ejection Method

    Directory of Open Access Journals (Sweden)

    DONG Wei

    2018-02-01

    Full Text Available A novel technology called pulsated orifice ejection method(POEM and used for preparing mono-sized and high-precision spherical micro particles was introduced in this article. The working principle of the technique was illustrated and it was in two modes:low-melting point diaphragm mode and high-melting point rod mode, depending on the different melting points of materials. The particles prepared by POEM have the advantages of mono-sized, uniform and controllable particle size, high sphericity, and consistent thermal history. By introducing the application of particles prepared by this method, showing the huge application prospects of this technology in electronic packaging, bioengineering, micro-fabrication, rapid solidification analysis of metal droplets, additive manufacturing and so on.With the development of POEM, this technology is predicted to have wider prospects due to its unique characteristics.

  7. Preparation of Fe3O4Spherical Nanoporous Particles Facilitated by Polyethylene Glycol 4000

    Directory of Open Access Journals (Sweden)

    Wang Li-Li

    2009-01-01

    Full Text Available Abstract Much interest has been attracted to the magnetic materials with porous structure because of their unique properties and potential applications. In this report, Fe3O4nanoporous particles assembled from small Fe3O4nanoparticles have been prepared by thermal decomposition of iron acetylacetonate in the presence of polyethylene glycol 4000. The size of the spherical nanoporous particles is 100–200 nm. Surface area measurement shows that these Fe3O4nanoporous particles have a high surface area of 87.5 m2/g. Magnetization measurement and Mössbauer spectrum indicate that these particles are nearly superparamagnetic at room temperature. It is found that the morphology of the products is greatly influenced by polyethylene glycol concentration and the polymerization degree of polyethylene glycol. Polyethylene glycol molecules are believed to facilitate the formation of the spherical assembly.

  8. DNA adsorption characteristics of hollow spherical allophane nano-particles

    Science.gov (United States)

    Matsuura, Yoko; Iyoda, Fumitoshi; Hayashi, Shuhei; Arakawa, Shuichi; Okamoto, Masami; Hayashi, Hidetomo

    2014-05-01

    To understand the propensity of the natural allophane to adsorb the DNA molecules, the adsorption characteristics were assessed against a natural allophane, using single-stranded DNA (ss-DNA) and adenosine 5'-monophosphate (5'-AMP) as a reference molecule. The adsorption capacity of ss-DNA on AK70 exhibited one order of magnitude lower value as compared with that of 5'-AMP. The adsorption capacity of ss-DNA decreased with increasing pH due to the interaction generated between phosphate groups of ss-DNA and functional Al-OH groups on the wall perforations through deprotonation, associated with higher energy barrier for the adsorption of ss-DNA. The adsorption morphologies consisting of the individual ss-DNA with mono-layer coverage of the allophane clustered particle was successfully observed through TEM analysis.

  9. Precipitation of spherical and 'fiber-like' silver particles.

    Science.gov (United States)

    Lu, Lu; Goia, Dan V

    2013-10-01

    Silver nanoparticles with various sizes and shapes were prepared by adding silver nitrate to ascorbic acid solutions containing nitric acid and a dispersant (Daxad 11G). It is shown that the reaction environment significantly affects the nature of the interactions between silver ions and dispersant molecules. The stability of the Ag(+)/Daxad 11G intermediate species formed, which determines the reduction rate and, implicitly, the particle size and shape, is strongly affected by the dispersant/Ag(+) ratio and the concentration of nitric acid. Uniform highly dispersed Ag nanoparticles were obtained at high concentrations of HNO3, while lower acid concentrations favored the formation of 'fiber-like' metallic structures. The propensity for forming anisotropic silver structures is attributed to the planar structure and chromonic properties of dispersant molecules. Copyright © 2013 Elsevier Inc. All rights reserved.

  10. Atomic layer deposition of {HfO}_2 for integration into three-dimensional metal-insulator-metal devices

    Science.gov (United States)

    Assaud, Loïc; Pitzschel, Kristina; Barr, Maïssa K. S.; Petit, Matthieu; Monier, Guillaume; Hanbücken, Margrit; Santinacci, Lionel

    2017-12-01

    {HfO}_2 nanotubes have been fabricated via a template-assisted deposition process for further use in three-dimensional metal-insulator-metal (MIM) devices. {HfO}_2 thin layers were grown by Atomic Layer Deposition (ALD) in anodic alumina membranes (AAM). The ALD was carried out using tetrakis(ethylmethylamino)hafnium and water as Hf and O sources, respectively. Long exposure durations to the precursors have been used to maximize the penetration depth of the {HfO}_2 layer within the AAM and the effect of the process temperature was investigated. The morphology, the chemical composition, and the crystal structure were studied as a function of the deposition parameters using transmission and scanning electron microscopies, X-ray photoelectron spectroscopy, and X-ray diffraction, respectively. As expected, the {HfO}_2 layers grown at low-temperature (T = 150°C) were amorphous, while for a higher temperature (T= 250°C), polycrystalline films were observed. The electrical characterizations have shown better insulating properties for the layers grown at low temperature. Finally, {TiN}/ {HfO}_2/ {TiN} multilayers were grown in an AAM as proof-of-concept for three-dimensional MIM nanostructures.

  11. Spherical active coated nano-particles – impact of the electric Hertzian dipole orientation

    DEFF Research Database (Denmark)

    Arslanagic, Samel; Mostafavi, M.; Malureanu, Radu

    2011-01-01

    Spherical active coated nano-particles comprised of a silica nano-cylinder core covered with a plasmonic nano-shell are investigated with regard to their near- and far-field properties. The source of excitation is taken to be that of a tangential or a radial electric Hertizan dipole while three...

  12. Cr/alpha-Cr 2O3 monodispersed spherical core-shell particles based solar absorbers

    CSIR Research Space (South Africa)

    Khamlich, S

    2011-07-01

    Full Text Available as reported. The coated Cr/alpha-Cr 2O3 spherical particles on rough copper substrates by a simple self-assembly-like method were characterized by scanning electron microscopy, energy dispersive spectrometry, Raman spectroscopy, and diffuse reflectance UV...

  13. PROCESS INVESTIGATIONS OF SELECTIVE LASER SINTERING OF TITANIUM POWDER POROUS MATERIALS WITH SPHERICAL PARTICLES

    Directory of Open Access Journals (Sweden)

    R. E. Bykau

    2011-01-01

    Full Text Available The paper describes a technology of selective laser sintering of porous materials with complicated surface geometry of spherical titanium powders. A mechanism of contact formation between powder particles at SLS and its influence on the geometrical form of the obtained received materials have been investigated in the paper.

  14. Morphology and Photoluminescence of HfO2Obtained by Microwave-Hydrothermal

    Directory of Open Access Journals (Sweden)

    Cavalcante LS

    2009-01-01

    Full Text Available Abstract In this letter, we report on the obtention of hafnium oxide (HfO2 nanostructures by the microwave-hydrothermal method. These nanostructures were analyzed by X-ray diffraction (XRD, field-emission gum scanning electron microscopy (FEG-SEM, transmission electron microscopy (TEM, energy dispersive X-ray spectrometry (EDXS, ultraviolet–visible (UV–vis spectroscopy, and photoluminescence (PL measurements. XRD patterns confirmed that this material crystallizes in a monoclinic structure. FEG-SEM and TEM micrographs indicated that the rice-like morphologies were formed due to an increase in the effective collisions between the nanoparticles during the MH processing. The EDXS spectrum was used to verify the chemical compositional of this oxide. UV–vis spectrum revealed that this material have an indirect optical band gap. When excited with 488 nm wavelength at room temperature, the HfO2nanostructures exhibited only one broad PL band with a maximum at around 548 nm (green emission.

  15. Photovoltaic Enhancement with Ferroelectric HfO2Embedded in the Structure of Solar Cells

    Science.gov (United States)

    Eskandari, Rahmatollah; Malkinski, Leszek

    Enhancing total efficiency of the solar cells is focused on the improving one or all of the three main stages of the photovoltaic effect: absorption of the light, generation of the carriers and finally separation of the carriers. Ferroelectric photovoltaic designs target the last stage with large electric forces from polarized ferroelectric films that can be larger than band gap of the material and the built-in electric fields in semiconductor bipolar junctions. In this project we have fabricated very thin ferroelectric HfO2 films ( 10nm) doped with silicon using RF sputtering method. Doped HfO2 films were capped between two TiN layers ( 20nm) and annealed at temperatures of 800ºC and 1000ºC and Si content was varied between 6-10 mol. % using different size of mounted Si chip on hafnium target. Piezoforce microscopy (PFM) method proved clear ferroelectric properties in samples with 6 mol. % of Si that were annealed at 800ºC. Ferroelectric samples were poled in opposite directions and embedded in the structure of a cell and an enhancement in photovoltaic properties were observed on the poled samples vs unpoled ones with KPFM and I-V measurements. The current work is funded by the NSF EPSCoR LA-SiGMA project under award #EPS-1003897.

  16. Nanopore fabricated in pyramidal HfO2 film by dielectric breakdown method

    Science.gov (United States)

    Wang, Yifan; Chen, Qi; Deng, Tao; Liu, Zewen

    2017-10-01

    The dielectric breakdown method provides an innovative solution to fabricate solid-state nanopores on insulating films. A nanopore generation event via this method is considered to be caused by random charged traps (i.e., structural defects) and high electric fields in the membrane. Thus, the position and number of nanopores on planar films prepared by the dielectric breakdown method is hard to control. In this paper, we propose to fabricate nanopores on pyramidal HfO2 films (10-nm and 15-nm-thick) to improve the ability to control the location and number during the fabrication process. Since the electric field intensity gets enhanced at the corners of the pyramid-shaped film, the probability of nanopore occurrence at vertex and edge areas increases. This priority of appearance provides us chance to control the location and number of nanopores by monitoring a sudden irreversible discrete increase in current. The experimental results showed that the probability of nanopore occurrence decreases in an order from the vertex area, the edge area to the side face area. The sizes of nanopores ranging from 30 nm to 10 nm were obtained. Nanopores fabricated on the pyramid-shaped HfO2 film also showed an obvious ion current rectification characteristic, which might improve the nanopore performance as a biomolecule sequencing platform.

  17. HfO2 and SiO2 as barriers in magnetic tunneling junctions

    Science.gov (United States)

    Shukla, Gokaran; Archer, Thomas; Sanvito, Stefano

    2017-05-01

    SiO2 and HfO2 are both high-k, wide-gap semiconductors, currently used in the microelectronic industry as gate barriers. Here we investigate whether the same materials can be employed to make magnetic tunnel junctions, which in principle can be amenable for integration in conventional Si technology. By using a combination of density functional theory and the nonequilibrium Green's functions method for quantum transport we have studied the transport properties of Co [0001 ] /SiO2[001 ] /Co [0001 ] and Fe [001 ] /HfO2[001 ] /Fe [001 ] junctions. In both cases we found a quite large magnetoresistance, which is explained through the analysis of the real band structure of the magnets and the complex one of the insulator. We find that there is no symmetry spin filtering for the Co-based junction since the high transmission Δ2' band crosses the Fermi level, EF, for both spin directions. However, the fact that Co is a strong ferromagnet makes the orbital contribution to the two Δ2' spin subbands different, yielding magnetoresistance. In contrast for the Fe-based junction symmetry filtering is active for an energy window spanning between the Fermi level and 1 eV below EF, with Δ1 symmetry contributing to the transmission.

  18. Perpendicular magnetic anisotropy of CoFeB\\Ta bilayers on ALD HfO2

    Directory of Open Access Journals (Sweden)

    Bart F. Vermeulen

    2017-05-01

    Full Text Available Perpendicular magnetic anisotropy (PMA is an essential condition for CoFe thin films used in magnetic random access memories. Until recently, interfacial PMA was mainly known to occur in materials stacks with MgO\\CoFe(B interfaces or using an adjacent crystalline heavy metal film. Here, PMA is reported in a CoFeB\\Ta bilayer deposited on amorphous high-κ dielectric (relative permittivity κ=20 HfO2, grown by atomic layer deposition (ALD. PMA with interfacial anisotropy energy Ki up to 0.49 mJ/m2 appears after annealing the stacks between 200°C and 350°C, as shown with vibrating sample magnetometry. Transmission electron microscopy shows that the decrease of PMA starting from 350°C coincides with the onset of interdiffusion in the materials. High-κ dielectrics are potential enablers for giant voltage control of magnetic anisotropy (VCMA. The absence of VCMA in these experiments is ascribed to a 0.6 nm thick magnetic dead layer between HfO2 and CoFeB. The results show PMA can be easily obtained on ALD high-κ dielectrics.

  19. A better understanding of biomass co-firing by developing an advanced non-spherical particle tracking model

    DEFF Research Database (Denmark)

    Yin, Chungen; Rosendahl, Lasse Aistrup; Kær, Søren Knudsen

    2004-01-01

    . To better understand biomass co-firing and therefore improve the design for co-firing biomass in wall-fired burners, the most commonly used spherical particle shape assumption is not used here, which may deviate a lot from reality for big biomass particles. A sphere gives a minimum in terms of the surface......-gradient force. Since the drag and lift forces are both shape factor- and orientation-dependent, coupled particle rotation equations are resolved to update particle orientation. In the reaction of biomass particles, the actual particle surface area available and the average oxygen mass flux at particle surface......-area-to-volume ratio and thus experiences a totally different motion and reaction as a non-spherical particle. Therefore, an advanced non-spherical particle-tracking model is developed to calculate the motion and reaction of nonspherical biomass particles. The biomass particles are assumed as solid or hollow cylinders...

  20. Well controlled multiple resistive switching states in the Al local doped HfO2 resistive random access memory device

    Science.gov (United States)

    Chen, Y. S.; Chen, B.; Gao, B.; Liu, L. F.; Liu, X. Y.; Kang, J. F.

    2013-04-01

    The resistive switching behaviors in the sandwiched Ti/HfO2/Pt devices with different doping condition were systematically investigated. We show that, comparing with the undoped and the Al layer doped HfO2 devices, significant improvement of switching characteristics is achieved in the Al local doped HfO2 device, including uniformity, reliability, and operation current. As a result, well controlled multiple switching states are obtained in the local doping device by modulating the set current compliance or the maximal reset voltage, respectively. Our results suggest that the switching characteristics of HfO2 device are very closely related to the inducement and controlling of conductive filaments' growth in the dielectric layer, which can be considered in the optimization of resistive random access memory device design.

  1. Exciton polaritons of nano-spherical-particle photonic crystals in compound lattices

    Science.gov (United States)

    Zeng, Y.; Chen, X. S.; Lu, W.; Fu, Y.

    2006-02-01

    Nonlocal investigations are presented for exciton-photon coupling in three-dimensional nano-spherical-particle photonic crystals in compound lattices for a tailored dielectric environment to optimize the optical properties of nano particles. The photonic band structure can be modified by tuning the nano particle size and the distance between two interlacing identical face-centered sub-lattices making up the photonic crystal lattice. A complete photonic band gap with a gap-midgap ratio as large as 40.82% has been found in the wurzite structure under the current investigation.

  2. 3D numerical model of the spherical particle saltation in a channel with a rough fixed bed

    OpenAIRE

    Lukerchenko, Nikolay; Piatsevich, Ssiarhei; Chara, Zdenek; Vlasak, Pavel

    2009-01-01

    The paper describes a 3D numerical model of the spherical particle saltation. Two stages of particle saltation were distinguished – the particle free motion in water and the particle-bed collision. The particle motion consists of the translational and rotational particle motion. A stochastic method of calculation of the particle-bed collision was developed. The collision height and the contact point were defined as random variables. Impulse equations were used and the translational and angula...

  3. Study of strained-Si p-channel MOSFETs with HfO2 gate dielectric

    Science.gov (United States)

    Pradhan, Diana; Das, Sanghamitra; Dash, Tara Prasanna

    2016-10-01

    In this work, the transconductance of strained-Si p-MOSFETs with high-K dielectric (HfO2) as gate oxide, has been presented through simulation using the TCAD tool Silvaco-ATLAS. The results have been compared with a SiO2/strained-Si p-MOSFET device. Peak transconductance enhancement factors of 2.97 and 2.73 has been obtained for strained-Si p-MOSFETs in comparison to bulk Si channel p-MOSFETs with SiO2 and high-K dielectric respectively. This behavior is in good agreement with the reported experimental results. The transconductance of the strained-Si device at low temperatures has also been simulated. As expected, the mobility and hence the transconductance increases at lower temperatures due to reduced phonon scattering. However, the enhancements with high-K gate dielectric is less as compared to that with SiO2.

  4. Atomic Layer Deposition of Gd-Doped HfO2 Thin Films

    OpenAIRE

    Adelmann, C.; Tielens, H.; DEWULF, Daan; HARDY, An; Pierreux, D.; Swerts, J.; Rosseel, E.; Shi, X.; VAN BAEL, Marlies; Kittl, J. A.; Van Elshocht, S.

    2010-01-01

    GdxHf1-xOy thin films were deposited by atomic layer deposition (ALD) using tris(isopropyl-cyclopentadienyl) gadolinium [Gd((PrCp)-Pr-i)(3)] and HfCl4 in combination with H2O as an oxidizer. Growth curves showed a nearly ideal ALD behavior. The growth per individual Gd((PrCp)-Pr-i)(3)/H2O or HfCl4/H2O cycle was 0.55 A degrees, independent of the Gd/(Gd+Hf) composition x in the studied range. This indicates that the amount of HfO2 deposited during a HfCl4/H2O cycle was essentially identical to...

  5. Statistical analysis of random telegraph noise in HfO2-based RRAM devices in LRS

    Science.gov (United States)

    Puglisi, Francesco Maria; Pavan, Paolo; Larcher, Luca; Padovani, Andrea

    2015-11-01

    In this work, we present a thorough statistical characterization of Random Telegraph Noise (RTN) in HfO2-based Resistive Random Access Memory (RRAM) cells in Low Resistive State (LRS). Devices are tested under a variety of operational conditions. A Factorial Hidden Markov Model (FHMM) analysis is exploited to extrapolate the properties of the traps causing multi-level RTN in LRS. The trapping and de-trapping of charge carriers into/out of defects located in the proximity of the conductive filament results in a shielding effect on a portion of the conductive filament, leading to the observed RTN current fluctuations. It is found that both oxygen vacancies and oxygen ions defects may be responsible for the observed RTN. The variations of the current observed at subsequent set/reset cycles are instead attributed to the stochastic variations in the filament due to oxidation/reduction processes during reset and set operations, respectively.

  6. HfO2-based resistive switching memory with CNTs electrode for high density storage

    Science.gov (United States)

    Cheng, W. K.; Wang, F.; Han, Y. M.; Zhang, Z. C.; Zhao, J. S.; Zhang, K. L.

    2017-06-01

    In this paper, the HfO2-based resistive switching memory (RRAM) using carbon nanotubes (CNTs) as contact electrodes for high density integration is demonstrated. The Al/HfO2/CNTs devices show self-compliance, forming-free and low resistive state (LRS) nonlinearity with less than 130 nA reset current (Ireset). By contrast with the Al/HfO2/Ti devices, resistive switching behavior has been enhanced significantly by using CNTs electrode. For the Al/HfO2/CNTs devices, current-voltage (I-V) characteristics demonstrate that the current conduction in high resistive state (HRS) and low resistive state (LRS) is controlled by space-charge-limited current (SCLC) and trap-controlled SCLC mechanism, respectively.

  7. First principle simulations on the effects of oxygen vacancy in HfO2-based RRAM

    Directory of Open Access Journals (Sweden)

    Yuehua Dai

    2015-01-01

    Full Text Available HfO2-based resistive random access memory (RRAM takes advantage of oxygen vacancy (V o defects in its principle of operation. Since the change in resistivity of the material is controlled by the level of oxygen deficiency in the material, it is significantly important to study the performance of oxygen vacancies in formation of conductive filament. Excluding effects of the applied voltage, the Vienna ab initio simulation package (VASP is used to investigate the orientation and concentration mechanism of the oxygen vacancies based on the first principle. The optimal value of crystal orientation [010] is identified by means of the calculated isosurface plots of partial charge density, formation energy, highest isosurface value, migration barrier, and energy band of oxygen vacancy in ten established orientation systems. It will effectively influence the SET voltage, forming voltage, and the ON/OFF ratio of the device. Based on the results of orientation dependence, different concentration models are established along crystal orientation [010]. The performance of proposed concentration models is evaluated and analyzed in this paper. The film is weakly conductive for the samples deposited in a mixture with less than 4.167at.% of V o contents, and the resistive switching (RS phenomenon cannot be observed in this case. The RS behavior improves with an increase in the V o contents from 4.167at.% to 6.25at.%; nonetheless, it is found difficult to switch to a stable state. However, a higher V o concentration shows a more favorable uniformity and stability for HfO2-based RRAM.

  8. Strength of wet agglomerates of spherical particles: effects of friction and size distribution

    Science.gov (United States)

    Vo, Thanh-Trung; Mutabaruka, Patrick; Delenne, Jean-Yves; Nezamabadi, Saeid; Radjai, Farhang

    2017-06-01

    We investigate the mechanical behavior of wet granular agglomerates composed of spherical particles by means of molecular dynamics simulations. The capillary cohesion force is modeled as an attraction force at the contact between two particles and expressed as an explicit function of the gap and volume of the liquid bridge. We are interested in the effect of the friction coefficient between primary particles. The agglomerates are subjected to diametrical compression tests. We find that the deformation is ductile involving particle rearrangements. However, a well-defined stress peak is observed and the peak stress is used as a measure of the compressive strength of the agglomerate. The strength increases with friction coefficient but levels off at friction coefficients above 0.4. Furthermore, the compressive strength is an increasing function of particle size span.

  9. Importance of Variable Density and Non-Boussinesq Effects on the Drag of Spherical Particles

    Science.gov (United States)

    Ganguli, Swetava; Lele, Sanjiva

    2017-11-01

    What are the forces that act on a particle as it moves in a fluid? How do they change in the presence of significant heat transfer from the particle, a variable density fluid or gravity? Last year, using particle-resolved simulations we quantified these effects on a single spherical particle and on particles in periodic lattices when O(10-3) 50%) in the absolute drag are observed as λ approaches unity. Oppenheimer, et al. (2016) [1] have proposed a theoretical formula for the drag of a heated sphere at extremely low Re. We show that when Re >O(10), inertial effects completely dominate the drag while when Re zero volumetric dilation rate. In the limit of λ approaching 0 (Stokes' limit), the drag modification can also be captured as a correction to Stokes' drag using a suitable scaling based on the dilation rate. Stanford University - Predictive Science Academic Alliance Program (PSSAP II).

  10. Strength of wet agglomerates of spherical particles: effects of friction and size distribution

    Directory of Open Access Journals (Sweden)

    Vo Thanh-Trung

    2017-01-01

    Full Text Available We investigate the mechanical behavior of wet granular agglomerates composed of spherical particles by means of molecular dynamics simulations. The capillary cohesion force is modeled as an attraction force at the contact between two particles and expressed as an explicit function of the gap and volume of the liquid bridge. We are interested in the effect of the friction coefficient between primary particles. The agglomerates are subjected to diametrical compression tests. We find that the deformation is ductile involving particle rearrangements. However, a well-defined stress peak is observed and the peak stress is used as a measure of the compressive strength of the agglomerate. The strength increases with friction coefficient but levels off at friction coefficients above 0.4. Furthermore, the compressive strength is an increasing function of particle size span.

  11. Ultra-directional super-scattering of homogenous spherical particles with radial anisotropy

    CERN Document Server

    Liu, Wei

    2015-01-01

    We study the light scattering of homogenous radially-anisotropic spherical particles. It is shown that radial anisotropy can be employed to tune effectively the electric resonances, and thus enable flexible overlapping of electric and magnetic dipoles of various numbers, which leads to unidirectional forward super-scattering at different spectral positions. We further reveal that through adjusting the radial anisotropy parameters, electric and magnetic resonances of higher orders can be also made overlapped, thus further collimating the forward scattering lobes. The ultra-directional super-scattering we have obtained with individual homogenous radially anisotropic spherical particles may shed new light to the design of compact and efficient nanoantennas, which may find various applications in solar cells, bio-sensing and many other antenna based researches.

  12. Temperature Effects on a-IGZO Thin Film Transistors Using HfO2 Gate Dielectric Material

    Directory of Open Access Journals (Sweden)

    Yu-Hsien Lin

    2014-01-01

    Full Text Available This study investigated the temperature effect on amorphous indium gallium zinc oxide (a-IGZO thin film transistors (TFTs using hafnium oxide (HfO2 gate dielectric material. HfO2 is an attractive candidate as a high-κ dielectric material for gate oxide because it has great potential to exhibit superior electrical properties with a high drive current. In the process of integrating the gate dielectric and IGZO thin film, postannealing treatment is an essential process for completing the chemical reaction of the IGZO thin film and enhancing the gate oxide quality to adjust the electrical characteristics of the TFTs. However, the hafnium atom diffused the IGZO thin film, causing interface roughness because of the stability of the HfO2 dielectric thin film during high-temperature annealing. In this study, the annealing temperature was optimized at 200°C for a HfO2 gate dielectric TFT exhibiting high mobility, a high ION/IOFF ratio, low IOFF current, and excellent subthreshold swing (SS.

  13. Coexistence of different charge states in Ta-doped monoclinic HfO2: Theoretical and experimental approaches

    DEFF Research Database (Denmark)

    Taylor, M.A.; Alonso, R.E.; Errico, L.A.

    2010-01-01

    A combination of experiments and ab initio quantum-mechanical calculations has been applied to examine hyperfine interactions in Ta-doped hafnium dioxide. Although the properties of monoclinic HfO2 have been the subject of several earlier studies, some aspects remain open. In particular, time dif...

  14. Shape evolution of a core-shell spherical particle under hydrostatic pressure.

    Science.gov (United States)

    Colin, Jérôme

    2012-03-01

    The morphological evolution by surface diffusion of a core-shell spherical particle has been investigated theoretically under hydrostatic pressure when the shear modulii of the core and shell are different. A linear stability analysis has demonstrated that depending on the pressure, shear modulii, and radii of both phases, the free surface of the composite particle may be unstable with respect to a shape perturbation. A stability diagram finally emphasizes that the roughness development is favored in the case of a hard shell with a soft core.

  15. Fabrication of high-alloy powders consisting of spherical particles from ultradispersed components

    Science.gov (United States)

    Samokhin, A. V.; Fadeev, A. A.; Sinayskiy, M. A.; Alekseev, N. V.; Tsvetkov, Yu. V.; Arzhatkina, O. A.

    2017-07-01

    It is shown that powders of a model high alloy consisting of spherical particles 25-50 μm in size can be synthesized from a starting ultradispersed powder, which is made of a mixture of the alloy components and is fabricated by the magnesiothermal reduction of metal chlorides in the potassium chloride melt. The synthesis includes the stages of microgranulation of an ultradispersed powder, heat treatment of microgranules, classification of the microgranules with the separation of microgranule fraction of 25-50 μm, spheroidization of the separated fraction in a thermal plasma flow, and classification with the separation of a fraction of micro- and submicrometer-sized particles.

  16. Electrokinetic motion of a spherical polystyrene particle at a liquid-fluid interface.

    Science.gov (United States)

    Zhang, Junyan; Song, Yongxin; Li, Dongqing

    2018-01-01

    Electrokinetic movement of spherical polystyrene particles at different liquid-fluid interfaces was experimentally investigated in this paper. A novel method was developed to place the particles rightly at the interfaces formed in a large plastic container. The velocity was measured by an optical microscope. The experimental results show that the particles (3, 5 and 10μm in diameter) at the water-air interface, water-dodecane interface and NaCl solution-air interface move in the opposite direction of the applied electric field. The magnitude of the particles' velocity increases linearly with the increase in the applied electric field. Moreover, for particles of the same size, the electrokinetic velocity at the liquid-fluid interfaces is larger than particles' electrophoretic velocity in the bulk liquid phase. Under the same electric field, however, the electrokinetic velocity of smaller particles at the liquid-fluid interfaces is larger than that of larger particles. Such results are attributed to the surface charges at the liquid-fluid interface and the particle-liquid interface. Copyright © 2017 Elsevier Inc. All rights reserved.

  17. Size controllable synthesis of ultrafine spherical gold particles and their simulation of plasmonic and SERS behaviors

    Energy Technology Data Exchange (ETDEWEB)

    Yi, Zao [Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, Sichuan (China); College of Physics and Electronics, Central South University, Changsha 410083 (China); Science and Technology on Plasma Physics Laboratory, China Academy of Engineering Physics, Mianyang 621900 (China); Xu, Xibin [Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, Sichuan (China); College of Physics and Electronics, Central South University, Changsha 410083 (China); Luo, Jiangshan; Li, Xibo [Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, Sichuan (China); Science and Technology on Plasma Physics Laboratory, China Academy of Engineering Physics, Mianyang 621900 (China); Yi, Yong [Joint Laboratory for Extreme Conditions Matter Properties, Southwest University of Science and Technology and Research Center of Laser Fusion, Mianyang (China); Jiang, Xiaodong [Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, Sichuan (China); Yi, Yougen, E-mail: yougenyi@mail.csu.edu.cn [College of Physics and Electronics, Central South University, Changsha 410083 (China); Tang, Yongjian [Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, Sichuan (China); Science and Technology on Plasma Physics Laboratory, China Academy of Engineering Physics, Mianyang 621900 (China)

    2014-04-01

    A simple and reproducible way was explored to synthesize quasi-spherical gold particles with different size distributions in water by rapidly adding a mixture solution of HAuCl{sub 4}, sodium citrate, and a trace amount of silver nitrate. By careful tuning of the reaction parameters, mono-disperse gold particles with the diameter of 5–220 nm can be obtained controllably. The particle size of 130 nm for the particles film showed the highest SERS activity with the 632.8 nm excitation. The theoretical calculations of the UV–vis extinction spectra can be directly compared with experiments by using the discrete-dipole approximation (DDA). Control of nanostructure shape allows optimization of plasmon resonance for molecular detection and spectroscopy.

  18. Electrokinetic motion of a spherical micro particle at an oil-water interface in microchannel.

    Science.gov (United States)

    Wang, Chengfa; Li, Mengqi; Song, Yongxin; Pan, Xinxiang; Li, Dongqing

    2017-09-19

    The electrokinetic motion of a negatively charged spherical particle at an oil-water interface in a microchannel is numerically investigated and analyzed in this paper. A three-dimensional (3D) transient numerical model is developed to simulate the particle electrokinetic motion. The channel wall, the surface of the particle and the oil-water interface are all considered negatively charged. The effects of the direct current (DC) electric field, the zeta potentials of the particle-water interface and the oil-water interface, and the dynamic viscosity ratio of oil to water on the velocity of the particle are studied in this paper. In addition, the influences of the particle size are also discussed. The simulation results show that the micro-particle with a small value of negative zeta potential moves in the same direction of the external electric field. However, if the zeta potential value of the particle-water interface is large enough, the moving direction of the particle is opposite to that of the electric field. The velocity of the particle at the interface increases with the increase in the electric field strength and the particle size, but decreases with the increase in the dynamic viscosity ratio of oil to water, and the absolute value of the negative zeta potentials of both the particle-water interface and the oil-water interface. This work is the first numerical study of the electrokinetic motion of a charged particle at an oil-water interface in a microchannel. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Carbon-coated ZnO mat passivation by atomic-layer-deposited HfO2 as an anode material for lithium-ion batteries.

    Science.gov (United States)

    Jung, Mi-Hee

    2017-11-01

    ZnO has had little consideration as an anode material in lithium-ion batteries compared with other transition-metal oxides due to its inherent poor electrical conductivity and large volume expansion upon cycling and pulverization of ZnO-based electrodes. A logical design and facile synthesis of ZnO with well-controlled particle sizes and a specific morphology is essential to improving the performance of ZnO in lithium-ion batteries. In this paper, a simple approach is reported that uses a cation surfactant and a chelating agent to synthesize three-dimensional hierarchical nanostructured carbon-coated ZnO mats, in which the ZnO mats are composed of stacked individual ZnO nanowires and form well-defined nanoporous structures with high surface areas. In order to improve the performance of lithium-ion batteries, HfO2 is deposited on the carbon-coated ZnO mat electrode via atomic layer deposition. Lithium-ion battery devices based on the carbon-coated ZnO mat passivation by atomic layer deposited HfO2 exhibit an excellent initial discharge and charge capacities of 2684.01 and 963.21mAhg(-1), respectively, at a current density of 100mAg(-1) in the voltage range of 0.01-3V. They also exhibit cycle stability after 125 cycles with a capacity of 740mAhg(-1) and a remarkable rate capability. Copyright © 2017 Elsevier Inc. All rights reserved.

  20. Columnar structure formation of a dilute suspension of settling spherical particles in a quiescent fluid

    Science.gov (United States)

    Huisman, Sander G.; Barois, Thomas; Bourgoin, Mickaël; Chouippe, Agathe; Doychev, Todor; Huck, Peter; Morales, Carla E. Bello; Uhlmann, Markus; Volk, Romain

    2016-11-01

    The settling of heavy spherical particles in a column of quiescent fluid is investigated. The performed experiments cover a range of Galileo numbers (110 ≤Ga≤310 ) for a fixed density ratio of Γ =ρp/ρf=2.5 . In this regime the particles are known to show a variety of motions [Jenny, Dušek, and Bouchet, Instabilities and transition of a sphere falling or ascending freely in a Newtonian fluid, J. Fluid Mech. 508, 201 (2004), 10.1017/S0022112004009164]. It is known that the wake undergoes several transitions for increasing Ga resulting in particle motions that are successively vertical, oblique, oblique oscillating, and finally chaotic. Not only does this change the trajectory of single, isolated, settling particles, but it also changes the dynamics of a swarm of particles as collective effects become important even for dilute suspensions with volume fraction up to ΦV=O (10-3) , which are investigated in this work. Multicamera recordings of settling particles are recorded and tracked over time in three dimensions. A variety of analyses are performed and show a strong clustering behavior. The distribution of the cell areas of the Voronoï tessellation in the horizontal plane is compared to that of a random distribution of particles and shows clear clustering. Moreover, a negative correlation was found between the Voronoï area and the particle velocity; clustered particles fall faster. In addition, the angle between adjacent particles and the vertical is calculated and compared to a homogeneous distribution of particles, clear evidence of vertical alignment of particles is found. The experimental findings are compared to simulations.

  1. Electrokinetics of charged spherical colloidal particles taking into account the effect of ion size constraints.

    Science.gov (United States)

    López-García, J J; Aranda-Rascón, M J; Grosse, C; Horno, J

    2011-04-01

    The electrokinetic properties of suspended spherical particles are examined using a modified standard electrokinetic model, which takes into account the finite ion size and considers that the minimum approach distance of ions to the particle surface need not be equal to their effective radius in the bulk solution. We calculate the conductivity increment and the electrophoretic mobility and present a detailed interpretation of the obtained results, based on the analysis of the equilibrium and field-induced ion concentrations, as well as the convective fluid flow in the neighborhood of the particle surface. We show that when charge reversal takes place, the sign of the concentration polarization remains unchanged while the sign of the electrophoretic mobility only changes under favorable circumstances. Copyright © 2010 Elsevier Inc. All rights reserved.

  2. Computational study of the effect of gradient magnetic field in navigation of spherical particles

    Science.gov (United States)

    Karvelas, E. G.; Lampropoulos, N. K.; Papadimitriou, D. I.; Karakasidis, T. E.; Sarris, I. E.

    2017-11-01

    The use of spherical magnetic nanoparticles that are coated with drugs and can be navigated in arteries to attack tumors is proposed as an alternative to chemotherapy. Navigation of particles is due to magnetic field gradients that may be produced in an MRI device. In the present work, a computational study for the evaluation of the magnitude of the gradient magnetic field for particles navigation in Y bifurcations is presented. For this purpose, the presented method solves for the fluid flow and includes all the important forces that act on the particles in their discrete motion. The method is based on an iteration algorithm that adjusts the gradient magnetic field to minimize the particles’ deviation from a desired trajectory. Using the above mentioned method, the appropriate range of the gradient magnetic field for optimum navigation of nanoparticles’s aggregation is found.

  3. The synthesis of clusters of iron oxides in mesopores of monodisperse spherical silica particles

    Science.gov (United States)

    Stovpiaga, E. Yu.; Eurov, D. A.; Kurdyukov, D. A.; Smirnov, A. N.; Yagovkina, M. A.; Grigorev, V. Yu.; Romanov, V. V.; Yakovlev, D. R.; Golubev, V. G.

    2017-08-01

    The method of obtaining nanoclusters α-Fe2O3 in the pores of monodisperse spherical particles of mesoporous silica ( mSiO2) by a single impregnation of the pores with a melt of crystalline hydrate of ferric nitrate and its subsequent thermal destruction has been proposed. Fe3O4 nanoclusters are synthesized from α-Fe2O3 in the pores by reducing in thermodynamically equilibrium conditions. Then particles containing Fe3O4 were annealed in oxygen for the conversion of Fe3O4 back to α-Fe2O3. In the result, the particles with the structure of the core-shell mSiO2/Fe3O4@ mSiO2/α-Fe2O3 are obtained. The composition and structure of synthesized materials as well as the field dependence of the magnetic moment on the magnetic field strength have been investigated.

  4. A non-iterative immersed boundary method for spherical particles of arbitrary density ratio

    Science.gov (United States)

    Tschisgale, Silvio; Kempe, Tobias; Fröhlich, Jochen

    2017-06-01

    In this paper an immersed boundary method with semi-implicit fluid-solid coupling for mobile particles of arbitrary density ratio is developed. The new scheme does not require any iterations to balance fluid forces and particle forces at the interface. A new formulation of the particle equations of motion is proposed which not only accounts for the particle itself but also for a Lagrangian layer surrounding the particle surface. Furthermore, it is shown by analytical considerations that the six equations for the linear and angular velocity of the spherical particle decouple which allows their sequential solution. On this basis a new time integration scheme is obtained which is unconditionally stable for all fluid-solid density ratios and enables large time steps, with Courant numbers around unity. The new scheme is extensively validated for various test cases and its convergence is assessed. An appealing issue is that compared to existing immersed boundary methods the new scheme only alters coefficients in the particle equations and the order of the steps, making it easy to implement in present codes with explicit coupling. This substantially extends the field of application of such methods.

  5. Experimental study of forces on freely moving spherical particles during resuspension into turbulent flow

    CERN Document Server

    Traugott, Hadar

    2015-01-01

    Turbulent resuspension is the process of lifting solid particles from the bottom by turbulent flow, ubiquitous in natural and industrial problems. The process is a sequence of events that start with an incipient motion when the particle is dislodged from its place, continue as sliding or rolling along the surface, and ending with the detachment of the particle from the surface and lifting it up into the flow. In this study we measure in details the motion of freely moving solid spherical particles along the bottom smooth wall under an oscillating grid turbulence and track them through the lift-off events. We measure simultaneously the Lagrangian trajectories of the particles and the flow tracers around them. We estimate the local flow parameters and extract the different force terms that act on a particle. For the particles of the diameter comparable with the Kolmogorov length scale, either sliding or rolling along the smooth wall under a zero-mean turbulent flow, we find that: i) the lift force is a dominant...

  6. Four-Bits-Per-Cell Operation in an HfO2 -Based Resistive Switching Device.

    Science.gov (United States)

    Kim, Gun Hwan; Ju, Hyunsu; Yang, Min Kyu; Lee, Dong Kyu; Choi, Ji Woon; Jang, Jae Hyuck; Lee, Sang Gil; Cha, Ik Su; Park, Bo Keun; Han, Jeong Hwan; Chung, Taek-Mo; Kim, Kyung Min; Hwang, Cheol Seong; Lee, Young Kuk

    2017-10-01

    The quadruple-level cell technology is demonstrated in an Au/Al2 O3 /HfO2 /TiN resistance switching memory device using the industry-standard incremental step pulse programming (ISPP) and error checking/correction (ECC) methods. With the highly optimistic properties of the tested device, such as self-compliance and gradual set-switching behaviors, the device shows 6σ reliability up to 16 states with a state current gap value of 400 nA for the total allowable programmed current range from 2 to 11 µA. It is demonstrated that the conventional ISPP/ECC can be applied to such resistance switching memory, which may greatly contribute to the commercialization of the device, especially competitively with NAND flash. A relatively minor improvement in the material and circuitry may enable even a five-bits-per-cell technology, which can hardly be imagined in NAND flash, whose state-of-the-art multiple-cell technology is only at three-level (eight states) to this day. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Mechanistic Insight into the Stability of HfO2-Coated MoS2 Nanosheet Anodes for Sodium Ion Batteries

    KAUST Repository

    Ahmed, Bilal

    2015-06-01

    It is demonstrated for the first time that surface passivation of 2D nanosheets of MoS2 by an ultrathin and uniform layer of HfO2 can significantly improve the cyclic performance of sodium ion batteries. After 50 charge/discharge cycles, bare MoS2 and HfO2 coated MoS2 electrodes deliver the specific capacity of 435 and 636 mAh g-1, respectively, at current density of 100 mA g-1. These results imply that batteries using HfO2 coated MoS2 anodes retain 91% of the initial capacity; in contrast, bare MoS2 anodes retain only 63%. Also, HfO2 coated MoS2 anodes show one of the highest reported capacity values for MoS2. Cyclic voltammetry and X-ray photoelectron spectroscopy results suggest that HfO2 does not take part in electrochemical reaction. The mechanism of capacity retention with HfO2 coating is explained by ex situ transmission electron microscope imaging and electrical impedance spectroscopy. It is illustrated that HfO2 acts as a passivation layer at the anode/electrolyte interface and prevents structural degradation during charge/discharge process. Moreover, the amorphous nature of HfO2 allows facile diffusion of Na ions. These results clearly show the potential of HfO2 coated MoS2 anodes, which performance is significantly higher than previous reports where bulk MoS2 or composites of MoS2 with carbonaceous materials are used. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Gas-phase reaction studies of dipositive hafnium and hafnium oxide ions: generation of the peroxide HfO2(2+).

    Science.gov (United States)

    Lourenço, Célia; Michelini, Maria del Carmen; Marçalo, Joaquim; Gibson, John K; Oliveira, Maria Conceição

    2012-12-27

    Fourier transform ion cyclotron resonance mass spectrometry was used to characterize the gas-phase reactivity of Hf dipositive ions, Hf(2+)and HfO(2+), toward several oxidants: thermodynamically facile O-atom donor N(2)O, ineffective donor CO, and intermediate donors O(2), CO(2), NO, and CH(2)O. The Hf(2+) ion exhibited electron transfer with N(2)O, O(2), NO, and CH(2)O, reflecting the high ionization energy of Hf(+). The HfO(2+) ion was produced by O-atom transfer to Hf(2+) from N(2)O, O(2), and CO(2), and the HfO(2)(2+) ion by O-atom transfer to HfO(2+) from N(2)O; these reactions were fairly efficient. Density functional theory revealed the structure of HfO(2)(2+) as a peroxide. The HfO(2)(2+) ion reacted by electron transfer with N(2)O, CO(2), and CO to give HfO(2)(+). Estimates were made for the second ionization energies of Hf (14.5 ± 0.5 eV), HfO (14.3 ± 0.5 eV), and HfO(2) (16.2 ± 0.5 eV), and also for the bond dissociation energies, D[Hf(2+)-O] = 686 ± 69 kJ mol(-1) and D[OHf(2+)-O] = 186 ± 98 kJ mol(-1). The computed bond dissociation energies, 751 and 270 kJ mol(-1), respectively, are within these experimental ranges. Additionally, it was found that HfO(2)(2+) oxidized CO to CO(2) and is thus a catalyst in the oxidation of CO by N(2)O and that Hf(2+) activates methane to produce a carbene, HfCH(2)(2+).

  9. Thermal conversion of filamentous potato virus X into spherical particles with different properties from virions.

    Science.gov (United States)

    Nikitin, Nikolai; Ksenofontov, Alexander; Trifonova, Ekaterina; Arkhipenko, Marina; Petrova, Ekaterina; Kondakova, Olga; Kirpichnikov, Mikhail; Atabekov, Joseph; Dobrov, Evgeny; Karpova, Olga

    2016-05-01

    We developed a method for the fast transformation of virions of tobacco mosaic virus (TMV) in so-called spherical particles (SPs) of different sizes. These SPs turned out to be highly useful for the preparation of different kinds of important biotechnological products. In this communication, we report that a representative of the flexuous helical virus group-potato virus X (PVX), produces SPs as well, but these SPs differ from TMV SPs in several important aspects. PVX SPs may be useful biotechnological devices. © 2016 Federation of European Biochemical Societies.

  10. Nonlinear dynamics of spherical particles in Poiseuille flow under creeping-flow condition.

    Science.gov (United States)

    Reddig, S; Stark, H

    2013-06-21

    We study the nonlinear dynamics of spherical colloids under the influence of a pressure driven flow at vanishing Reynolds number. The colloids are confined between two parallel planar walls with a distance comparable to the particle diameter and they interact hydrodynamically via the solvent. We show that the bounded Poiseuille flow gives rise to new classes of trajectories resulting in cross-streamline migration. Two particles moving on these new trajectories exhibit either bound or unbound states. In the first case they oscillate on closed trajectories in the center-of-mass frame. In the second case, they exhibit cross-swapping trajectories in addition to swapping trajectories which were already observed in unbounded or bounded linear shear flow. The different classes of trajectories occur depending on the initial positions of the two particles and their size. We present state diagrams in the lateral positions, where we categorize the trajectories and color code the oscillation frequencies of the bound states. Finally we discuss how the results on the two-particle system help to understand the stability of particle trains composed of several particles.

  11. Inertial migration regimes of spherical particles suspended in square tube flows

    Science.gov (United States)

    Shichi, Hiroyuki; Yamashita, Hiroshi; Seki, Junji; Itano, Tomoaki; Sugihara-Seki, Masako

    2017-04-01

    The inertial migration of neutrally buoyant spherical particles suspended in tube flows of square cross sections was investigated experimentally in the range of Reynolds numbers (Re) from 1 to 800 for particle-to-tube-size ratios from 0.075 to 0.175. Direct observations of the particle distribution in the cross section at various distances from the tube inlet revealed that at low Re, smaller than a certain critical value, particles were focused on four equilibrium positions, located at the center of channel faces, consistent with previous studies on microchannel flows, whereas at higher Re, larger than another critical value, four additional equilibrium positions were observed near the channel corners. At intermediate Re, between these two critical values, we observed new focusing positions of particles, located on a heteroclinic orbit joining the channel face and corner equilibrium positions. Comparing these results with corresponding numerical simulations, we examined the migration properties in detail and categorized their types. It was found that the critical Re values depended considerably on the particle-to-tube-size ratio.

  12. Enhancement of Endurance in HfO2-Based CBRAM Device by Introduction of a TaN Diffusion Blocking Layer

    KAUST Repository

    Chand, Umesh

    2017-08-05

    We propose a new method to improve resistive switching properties in HfO2 based CBRAM crossbar structure device by introducing a TaN thin diffusion blocking layer between the Cu top electrode and HfO2 switching layer. The Cu/TaN/HfO2/TiN device structure exhibits high resistance ratio of OFF/ON states without any degradation in switching during endurance test. The improvement in the endurance properties of the Cu/TaN/HfO2/TiN CBRAM device is thus attributed to the relatively low amount of Cu migration into HfO2 switching layer.

  13. Enhanced PEC performance of nanoporous Si photoelectrodes by covering HfO2 and TiO2 passivation layers.

    Science.gov (United States)

    Xing, Zhuo; Ren, Feng; Wu, Hengyi; Wu, Liang; Wang, Xuening; Wang, Jingli; Wan, Da; Zhang, Guozhen; Jiang, Changzhong

    2017-03-02

    Nanostructured Si as the high efficiency photoelectrode material is hard to keep stable in aqueous for water splitting. Capping a passivation layer on the surface of Si is an effective way of protecting from oxidation. However, it is still not clear in the different mechanisms and effects between insulating oxide materials and oxide semiconductor materials as passivation layers. Here, we compare the passivation effects, the photoelectrochemical (PEC) properties, and the corresponding mechanisms between the HfO2/nanoporous-Si and the TiO2/nanoporous-Si by I-V curves, Motte-schottky (MS) curves, and electrochemical impedance spectroscopy (EIS). Although the saturated photocurrent densities of the TiO2/nanoporous Si are lower than that of the HfO2/nanoporous Si, the former is more stable than the later.

  14. Electronic structure and relative stability of the coherent and semi-coherent HfO2/III-V interfaces

    Science.gov (United States)

    Lahti, A.; Levämäki, H.; Mäkelä, J.; Tuominen, M.; Yasir, M.; Dahl, J.; Kuzmin, M.; Laukkanen, P.; Kokko, K.; Punkkinen, M. P. J.

    2018-01-01

    III-V semiconductors are prominent alternatives to silicon in metal oxide semiconductor devices. Hafnium dioxide (HfO2) is a promising oxide with a high dielectric constant to replace silicon dioxide (SiO2). The potentiality of the oxide/III-V semiconductor interfaces is diminished due to high density of defects leading to the Fermi level pinning. The character of the harmful defects has been intensively debated. It is very important to understand thermodynamics and atomic structures of the interfaces to interpret experiments and design methods to reduce the defect density. Various realistic gap defect state free models for the HfO2/III-V(100) interfaces are presented. Relative energies of several coherent and semi-coherent oxide/III-V semiconductor interfaces are determined for the first time. The coherent and semi-coherent interfaces represent the main interface types, based on the Ga-O bridges and As (P) dimers, respectively.

  15. Nanoindentation investigation of HfO2 and Al2O3 films grown by atomic layer deposition

    Science.gov (United States)

    K. Tapily; Joseph E. Jakes; D. S. Stone; P. Shrestha; D. Gu; H. Baumgart; A. A. Elmustafa

    2008-01-01

    The challenges of reducing gate leakage current and dielectric breakdown beyond the 45 nm technology node have shifted engineers’ attention from the traditional and proven dielectric SiO2 to materials of higher dielectric constant also known as high-k materials such as hafnium oxide (HfO2) and aluminum oxide (Al2O3). These high-k materials are projected to...

  16. Discrete Element Simulation of Elastoplastic Shock Wave Propagation in Spherical Particles

    Directory of Open Access Journals (Sweden)

    M. Shoaib

    2011-01-01

    Full Text Available Elastoplastic shock wave propagation in a one-dimensional assembly of spherical metal particles is presented by extending well-established quasistatic compaction models. The compaction process is modeled by a discrete element method while using elastic and plastic loading, elastic unloading, and adhesion at contacts with typical dynamic loading parameters. Of particular interest is to study the development of the elastoplastic shock wave, its propagation, and reflection during entire loading process. Simulation results yield information on contact behavior, velocity, and deformation of particles during dynamic loading. Effects of shock wave propagation on loading parameters are also discussed. The elastoplastic shock propagation in granular material has many practical applications including the high-velocity compaction of particulate material.

  17. Theoretical Model for Predicting Moisture Ratio during Drying of Spherical Particles in a Rotary Dryer

    Directory of Open Access Journals (Sweden)

    F. T. Ademiluyi

    2013-01-01

    Full Text Available A mathematical model was developed for predicting the drying kinetics of spherical particles in a rotary dryer. Drying experiments were carried out by drying fermented ground cassava particles in a bench scale rotary dryer at inlet air temperatures of 115–230°C, air velocities of 0.83 m/s–1.55 m/s, feed mass of 50–500 g, drum drive speed of 8 rpm, and feed drive speed of 100 rpm to validate the model. The data obtained from the experiments were used to calculate the experimental moisture ratio which compared well with the theoretical moisture ratio calculated from the newly developed Abowei-Ademiluyi model. The comparisons and correlations of the results indicate that validation and performance of the established model are rather reasonable.

  18. Dimensional analysis and prediction of dielectrophoretic crossover frequency of spherical particles

    Directory of Open Access Journals (Sweden)

    Che-Kai Yeh

    2017-06-01

    Full Text Available The manipulation of biological cells and micrometer-scale particles using dielectrophoresis (DEP is an indispensable technique for lab-on-a-chip systems for many biological and colloidal science applications. However, existing models, including the dipole model and numerical simulations based on Maxwell stress tensor (MST, cannot achieve high accuracy and high computation efficiency at the same time. The dipole model is widely used and provides adequate predictions on the crossover frequency of submicron particles, but cannot predict the crossover frequency for larger particles accurately; on the other hand, the MST method offers high accuracy for a wide variety of particle sizes and shapes, but is time-consuming and may lack predictive understanding of the interplay between key parameters. Here we present a mathematical model, using dimensional analysis and the Buckingham pi theorem, that permits high accuracy and efficiency in predicting the crossover frequency of spherical particles. The curve fitting and calculation are performed using commercial packages OriginLab and MATLAB, respectively. In addition, through this model we also can predict the conditions in which no crossover frequency exists. Also, we propose a pair of dimensionless parameters, forming a functional relation, that provide physical insights into the dependency of the crossover frequency on five key parameters. The model is verified under several scenarios using comprehensive MST simulations by COMSOL Multiphysics software (COMSOL, Inc. and some published experimental data.

  19. Dimensional analysis and prediction of dielectrophoretic crossover frequency of spherical particles

    Science.gov (United States)

    Yeh, Che-Kai; Juang, Jia-Yang

    2017-06-01

    The manipulation of biological cells and micrometer-scale particles using dielectrophoresis (DEP) is an indispensable technique for lab-on-a-chip systems for many biological and colloidal science applications. However, existing models, including the dipole model and numerical simulations based on Maxwell stress tensor (MST), cannot achieve high accuracy and high computation efficiency at the same time. The dipole model is widely used and provides adequate predictions on the crossover frequency of submicron particles, but cannot predict the crossover frequency for larger particles accurately; on the other hand, the MST method offers high accuracy for a wide variety of particle sizes and shapes, but is time-consuming and may lack predictive understanding of the interplay between key parameters. Here we present a mathematical model, using dimensional analysis and the Buckingham pi theorem, that permits high accuracy and efficiency in predicting the crossover frequency of spherical particles. The curve fitting and calculation are performed using commercial packages OriginLab and MATLAB, respectively. In addition, through this model we also can predict the conditions in which no crossover frequency exists. Also, we propose a pair of dimensionless parameters, forming a functional relation, that provide physical insights into the dependency of the crossover frequency on five key parameters. The model is verified under several scenarios using comprehensive MST simulations by COMSOL Multiphysics software (COMSOL, Inc.) and some published experimental data.

  20. Spherical silica particles decorated with graphene oxide nanosheets as a new sorbent in inorganic trace analysis.

    Science.gov (United States)

    Sitko, Rafal; Zawisza, Beata; Talik, Ewa; Janik, Paulina; Osoba, Grzegorz; Feist, Barbara; Malicka, Ewa

    2014-06-27

    Graphene oxide (GO) is a novel material with excellent adsorptive properties. However, the very small particles of GO can cause serious problems is solid-phase extraction (SPE) such as the high pressure in SPE system and the adsorbent loss through pores of frit. These problems can be overcome by covalently binding GO nanosheets to a support. In this paper, GO was covalently bonded to spherical silica by coupling the amino groups of spherical aminosilica and the carboxyl groups of GO (GO@SiO2). The successful immobilization of GO nanosheets on the aminosilica was confirmed by scanning electron microscopy and X-ray photoelectron spectroscopy. The spherical particle covered by GO with crumpled silk wave-like carbon sheets are an ideal sorbent for SPE of metal ions. The wrinkled structure of the coating results in large surface area and a high extractive capacity. The adsorption bath experiment shows that Cu(II) and Pb(II) can be quantitatively adsorbed at pH 5.5 with maximum adsorption capacity of 6.0 and 13.6 mg g(-1), respectively. Such features of GO nanosheets as softness and flexibility allow achieving excellent contact with analyzed solution in flow-rate conditions. In consequence, the metal ions can be quantitatively preconcentrated from high volume of aqueous samples with excellent flow-rate. SPE column is very stable and several adsorption-elution cycles can be performed without any loss of adsorptive properties. The GO@SiO2 was used for analysis of various water samples by flame atomic absorption spectrometry with excellent enrichment factors (200-250) and detection limits (0.084 and 0.27 ng mL(-1) for Cu(II) and Pb(II), respectively). Copyright © 2014 Elsevier B.V. All rights reserved.

  1. Investigations on new carbon-based nanohybrids combining carbon nanotubes, HfO2 and ZnO nanoparticles

    Science.gov (United States)

    Rauwel, P.; Galeckas, A.; Salumaa, M.; Aasna, A.; Ducroquet, F.; Rauwel, E.

    2017-02-01

    In this work, we present two types of hybrid materials. The first hybrid material is a combination of carbon nanotubes (CNT) with HfO2 nanoparticles. The latter constituent on its own exhibits unusual visible photoluminescence, which is in stark contrast to non-luminescent HfO2 in the bulk form. The small size of HfO2 nanoparticles, 2.6 nm in average, suggests surface-defect related origin of the observed photoluminescence. The other hybrid material is CNT-ZnO with the embedded ZnO nanoparticles ranging from 50nm to 100nm in size. ZnO represents a direct bandgap semiconductor renowned as highly-luminescent in a broad spectral range. The visible region is attributed to luminescence involving deep-level defects, and hence depends on the synthesis conditions. In this study we compare the morphology of the two hybrid materials with transmission electron microscopy. We further compare the photoluminescence properties and the influence of the CNT coupling on enhancing or suppressing defect related emissions. Finally, we present a novel hybrid material CNT-HfO2 capable of producing a photocurrent under zero bias.

  2. Effect of heat treatment on properties of HfO2 film deposited by ion-beam sputtering

    Science.gov (United States)

    Liu, Huasong; Jiang, Yugang; Wang, Lishuan; Li, Shida; Yang, Xiao; Jiang, Chenghui; Liu, Dandan; Ji, Yiqin; Zhang, Feng; Chen, Deying

    2017-11-01

    The effects of atmosphere heat treatment on optical, stress, and microstructure properties of an HfO2 film deposited by ion-beam sputtering were systematically researched. The relationships among annealing temperature and refractive index, extinction coefficient, physical thickness, forbidden-band width, tape trailer width, Urbach energy, crystal phase structure, and stress were assessed. The results showed that 400 °C is the transformation point, and the microstructure of the HfO2 film changed from an amorphous into mixed-phase structure. Multistage phonons appeared on the HfO2 film, and the trends of the refractive index, extinction coefficient, forbidden-band width change, and Urbach energy shifted from decrease to increase. With the elevation of the annealing temperature, the film thickness increased monotonously, the compressive stress gradually turned to tensile stress, and the transformation temperature point for the stress was between 200 °C and 300 °C. Therefore, the change in the stress is the primary cause for the shifts in thin-film thickness.

  3. Dynamics of a spherical particle in an acoustic field: A multiscale approach

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Jin-Han, E-mail: J.H.Xie@ed.ac.uk; Vanneste, Jacques [School of Mathematics and Maxwell Institute for Mathematical Sciences, University of Edinburgh, Edinburgh EH9 3JZ (United Kingdom)

    2014-10-15

    A rigid spherical particle in an acoustic wave field oscillates at the wave period but has also a mean motion on a longer time scale. The dynamics of this mean motion is crucial for numerous applications of acoustic microfluidics, including particle manipulation and flow visualisation. It is controlled by four physical effects: acoustic (radiation) pressure, streaming, inertia, and viscous drag. In this paper, we carry out a systematic multiscale analysis of the problem in order to assess the relative importance of these effects depending on the parameters of the system that include wave amplitude, wavelength, sound speed, sphere radius, and viscosity. We identify two distinguished regimes characterised by a balance among three of the four effects, and we derive the equations that govern the mean particle motion in each regime. This recovers and organises classical results by King [“On the acoustic radiation pressure on spheres,” Proc. R. Soc. A 147, 212–240 (1934)], Gor'kov [“On the forces acting on a small particle in an acoustical field in an ideal fluid,” Sov. Phys. 6, 773–775 (1962)], and Doinikov [“Acoustic radiation pressure on a rigid sphere in a viscous fluid,” Proc. R. Soc. London A 447, 447–466 (1994)], clarifies the range of validity of these results, and reveals a new nonlinear dynamical regime. In this regime, the mean motion of the particle remains intimately coupled to that of the surrounding fluid, and while viscosity affects the fluid motion, it plays no part in the acoustic pressure. Simplified equations, valid when only two physical effects control the particle motion, are also derived. They are used to obtain sufficient conditions for the particle to behave as a passive tracer of the Lagrangian-mean fluid motion.

  4. dc Electrokinetics for spherical particles in salt-free concentrated suspensions including ion size effects.

    Science.gov (United States)

    Roa, Rafael; Carrique, Félix; Ruiz-Reina, Emilio

    2011-11-21

    We study the electrophoretic mobility of spherical particles and the electrical conductivity in salt-free concentrated suspensions including finite ion size effects. An ideal salt-free suspension is composed of just charged colloidal particles and the added counterions that counterbalance their surface charge. In a very recent paper [Roa et al., Phys. Chem. Chem. Phys., 2011, 13, 3960-3968] we presented a model for the equilibrium electric double layer for this kind of suspensions considering the size of the counterions, and now we extend this work to analyze the response of the suspension under a static external electric field. The numerical results show the high importance of such corrections for moderate to high particle charges, especially when a region of closest approach of the counterions to the particle surface is considered. The present work sets the basis for further theoretical models with finite ion size corrections, concerning particularly the ac electrokinetics and rheology of such systems. This journal is © the Owner Societies 2011

  5. SnO2 anode surface passivation by atomic layer deposited HfO2 improves li-ion battery performance

    KAUST Repository

    Yesibolati, Nulati

    2014-03-14

    For the first time, it is demonstrated that nanoscale HfO2 surface passivation layers formed by atomic layer deposition (ALD) significantly improve the performance of Li ion batteries with SnO2-based anodes. Specifically, the measured battery capacity at a current density of 150 mAg -1 after 100 cycles is 548 and 853 mAhg-1 for the uncoated and HfO2-coated anodes, respectively. Material analysis reveals that the HfO2 layers are amorphous in nature and conformably coat the SnO2-based anodes. In addition, the analysis reveals that ALD HfO2 not only protects the SnO2-based anodes from irreversible reactions with the electrolyte and buffers its volume change, but also chemically interacts with the SnO2 anodes to increase battery capacity, despite the fact that HfO2 is itself electrochemically inactive. The amorphous nature of HfO2 is an important factor in explaining its behavior, as it still allows sufficient Li diffusion for an efficient anode lithiation/delithiation process to occur, leading to higher battery capacity. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Thickness scaling of atomic-layer-deposited HfO2 films and their application to wafer-scale graphene tunnelling transistors.

    Science.gov (United States)

    Jeong, Seong-Jun; Gu, Yeahyun; Heo, Jinseong; Yang, Jaehyun; Lee, Chang-Seok; Lee, Min-Hyun; Lee, Yunseong; Kim, Hyoungsub; Park, Seongjun; Hwang, Sungwoo

    2016-02-10

    The downscaling of the capacitance equivalent oxide thickness (CET) of a gate dielectric film with a high dielectric constant, such as atomic layer deposited (ALD) HfO2, is a fundamental challenge in achieving high-performance graphene-based transistors with a low gate leakage current. Here, we assess the application of various surface modification methods on monolayer graphene sheets grown by chemical vapour deposition to obtain a uniform and pinhole-free ALD HfO2 film with a substantially small CET at a wafer scale. The effects of various surface modifications, such as N-methyl-2-pyrrolidone treatment and introduction of sputtered ZnO and e-beam-evaporated Hf seed layers on monolayer graphene, and the subsequent HfO2 film formation under identical ALD process parameters were systematically evaluated. The nucleation layer provided by the Hf seed layer (which transforms to the HfO2 layer during ALD) resulted in the uniform and conformal deposition of the HfO2 film without damaging the graphene, which is suitable for downscaling the CET. After verifying the feasibility of scaling down the HfO2 thickness to achieve a CET of ~1.5 nm from an array of top-gated metal-oxide-graphene field-effect transistors, we fabricated graphene heterojunction tunnelling transistors with a record-low subthreshold swing value of <60 mV/dec on an 8" glass wafer.

  7. Topological defects in an unconfined nematic fluid induced by single and double spherical colloidal particles

    Science.gov (United States)

    Wang, Yiwei; Zhang, Pingwen; Chen, Jeff Z. Y.

    2017-10-01

    We present numerical solutions to the Landau-de Gennes free-energy model under the one-constant approximation for systems of single and double spherical colloidal particles immersed in an otherwise uniformly aligned nematic liquid crystal. A perfect homeotropic surface anchoring of liquid-crystal molecules on the spherical surface is considered. A large parameter space is carefully examined, including those in the free-energy model and those describing the dimer configurations and the background liquid-crystal orientation. The stability of the resulting liquid-crystal defects appearing in the neighborhood of the colloidal dimer pair is analyzed in light of the numerical results for their free energies. A number of scenarios are considered: a free dimer pair in a nematic fluid where the free-energy ground states are described in terms of a phase diagram, and a constrained dimer pair where the interparticle distance and the relative orientation of the distance vector to the nematic director can be manipulated. We pay particular attention to the nonsymmetric solutions, which yield several metastable defect states that can be observed in real systems. The high-precision numerical calculations are based on a spectral method, which is an enabling factor that allows us to compare the subtle difference in the free energies of different defect structures.

  8. Shape effects on time-scale divergence at athermal jamming transition of frictionless non-spherical particles

    Science.gov (United States)

    Yuan, Ye; Jin, Weiwei; Liu, Lufeng; Li, Shuixiang

    2017-10-01

    The critical behaviors of a granular system at the jamming transition have been extensively studied from both mechanical and thermodynamic perspectives. In this work, we numerically investigate the jamming behaviors of a variety of frictionless non-spherical particles, including spherocylinder, ellipsoid, spherotetrahedron and spherocube. In particular, for a given particle shape, a series of random configurations at different fixed densities are generated and relaxed to minimize interparticle overlaps using the relaxation algorithm. We find that as the jamming point (i.e., point J) is approached, the number of iteration steps (defined as the ;time-scale; for our systems) required to completely relax the interparticle overlaps exhibits a clear power-law divergence. The dependence of the detailed mathematical form of the power-law divergence on particle shapes is systematically investigated and elucidated, which suggests that the shape effects can be generally categorized as elongation and roundness. Importantly, we show the jamming transition density can be accurately determined from the analysis of time-scale divergence for different non-spherical shapes, and the obtained values agree very well with corresponding ones reported in literature. Moreover, we study the plastic behaviors of over-jammed packings of different particles under a compression-expansion procedure and find that the jamming of ellipsoid is much more robust than other non-spherical particles. This work offers an alternative approximate procedure besides conventional packing algorithms for studying athermal jamming transition in granular system of frictionless non-spherical particles.

  9. RUSHMAPS: Real-Time Uploadable Spherical Harmonic Moment Analysis for Particle Spectrometers

    Science.gov (United States)

    Figueroa-Vinas, Adolfo

    2013-01-01

    programmable gate arrays), and DSP (digital signal processing) elements. The fundamental computational algorithm de constructs 3D velocity distributions in terms of spherical harmonic spectral coefficients (which are analogous to a Fourier sine-cosine decomposition), but uses instead spherical harmonics Legendre polynomial orthogonal functions as a basis for the expansion, portraying each 2D angular distribution at every energy or, geometrically, spherical speed-shell swept by the particle spectrometer. Optionally, these spherical harmonic spectral coefficients may be telemetered to the ground. These will provide a smoothed description of the velocity distribution function whose quality will depend on the number of coefficients determined. Successfully implemented on the GSFC-developed processor, the capability to integrate the proposed methodology with both heritage and anticipated future plasma particle spectrometer designs is demonstrated (with sufficiently detailed design analysis to advance TRL) to show specific science relevancy with future HSD (Heliophysics Science Division) solar-interplanetary, planetary missions, sounding rockets and/or CubeSat missions.

  10. Electrical four-point probing of spherical metallic thin films coated onto micron sized polymer particles

    Energy Technology Data Exchange (ETDEWEB)

    Pettersen, Sigurd R., E-mail: sigurd.r.pettersen@ntnu.no, E-mail: jianying.he@ntnu.no; Stokkeland, August Emil; Zhang, Zhiliang; He, Jianying, E-mail: sigurd.r.pettersen@ntnu.no, E-mail: jianying.he@ntnu.no [NTNU Nanomechanical Lab, Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), NO-7491 Trondheim (Norway); Kristiansen, Helge [NTNU Nanomechanical Lab, Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), NO-7491 Trondheim (Norway); Conpart AS, Dragonveien 54, NO-2013 Skjetten (Norway); Njagi, John; Goia, Dan V. [Center for Advanced Materials Processing, Clarkson University, Potsdam, New York 13699-5814 (United States); Redford, Keith [Conpart AS, Dragonveien 54, NO-2013 Skjetten (Norway)

    2016-07-25

    Micron-sized metal-coated polymer spheres are frequently used as filler particles in conductive composites for electronic interconnects. However, the intrinsic electrical resistivity of the spherical thin films has not been attainable due to deficiency in methods that eliminate the effect of contact resistance. In this work, a four-point probing method using vacuum compatible piezo-actuated micro robots was developed to directly investigate the electric properties of individual silver-coated spheres under real-time observation in a scanning electron microscope. Poly(methyl methacrylate) spheres with a diameter of 30 μm and four different film thicknesses (270 nm, 150 nm, 100 nm, and 60 nm) were investigated. By multiplying the experimental results with geometrical correction factors obtained using finite element models, the resistivities of the thin films were estimated for the four thicknesses. These were higher than the resistivity of bulk silver.

  11. On the Effective Thermal Conductivity of Porous Packed Beds with Uniform Spherical Particles

    Science.gov (United States)

    Kandula, Max

    2010-01-01

    Point contact models for the effective thermal conductivity of porous media with uniform spherical inclusions have been briefly reviewed. The model of Zehner and Schlunder (1970) has been further validated with recent experimental data over a broad range of conductivity ratio from 8 to 1200 and over a range of solids fraction up to about 0.8. The comparisons further confirm the validity of Zehner-Schlunder model, known to be applicable for conductivity ratios less than about 2000, above which area contact between the particles becomes significant. This validation of the Zehner-Schlunder model has implications for its use in the prediction of the effective thermal conductivity of water frost (with conductivity ratio around 100) which arises in many important areas of technology.

  12. Entropy generation during the quasi-steady burning of spherical fuel particles

    Energy Technology Data Exchange (ETDEWEB)

    Raghavan, V.; Gogos, G. [Department of Mechanical Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588 (United States); Babu, V.; Sundararajan, T. [Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai 600036 (India)

    2007-06-15

    Entropy generation during the quasi-steady combustion of spherical liquid fuel particles has been presented in detail. The effects of freestream velocity, particle diameter, ambient temperature and gravity, on the entropy generation rate, have been discussed in detail. In the range of sub-critical freestream velocity, where an envelope flame is present, the entropy generation rate presents a minimum value. At a critical velocity, where the flame transition occurs, the entropy generation rate reaches a maximum value. Flame transition significantly affects the entropy generation rate, which suffers a sharp decrease in its value after the transition. Heat transfer and chemical reaction contribute almost equally to the total entropy generation rate. When normal gravity is considered in an upward flow configuration, there is an increase in the entropy generation rate as compared to the zero gravity case. The effect of gravity poses a complex variation pattern in the entropy generation rate, for a downward flow configuration. The entropy generation rate decreases with increasing ambient temperature. The entropy generation rate increases with the particle diameter. A correlation has been presented for the non-dimensional entropy generation number as a function of Froude number. (author)

  13. Role of non-convexity in characterizing single-scattering properties for ensembles of non-spherical precipitation particles

    Science.gov (United States)

    Kuo, K.; Clune, T.; Pearson, C.; Olson, W. S.; Skofronick-Jackson, G.; Gravner, J.; Griffeath, D.

    2010-12-01

    This study improves upon an earlier, preliminary study using only three size bins based on maximum diameter in which it is found that the single-scattering properties of ensembles of non-spherical precipitation particles can be better characterized by considering the non-convexity of these particles. The difficulty of retrievals involving non-spherical particles stems not only from the fact that these particles are not spherical but also the fact that the shape composition of an ensemble of particles is usually unknown and the possibility of its mixture is infinite. Being able to adequately characterize the single-scattering properties of ensembles involving these non-spherical particles with as few parameters as possible is at the heart of solving this thorny remote sensing problem. Inspired by how well three parameters, i.e. water content, effective radius, and effective variance (or their equivalent), characterize the single-scattering properties of an ensemble of spherical particles of varying sizes, we set out to find additional parameters that generalize these three for ensembles of non-spherical particles. We find that a non-convexity measure appears to be one of these additional parameters. Non-convexity is expressed as a ratio of two effective radii derived from the moments of a given particle size distribution (PSD), each of which is in essence a ratio of ensemble particle volume to area. The effective radius in the numerator (denoted as rA) of the non-convexity ratio is based on the projection area of the particle ensemble whereas the one in the denominator (denoted as rS) is based on the surface area. In the preliminary study with PSDs having only three size bins, it is found that variations in the single-scattering properties, such as the scattering and extinction coefficients, the asymmetry factor, and even the scattering phase function, of a particle ensemble with a specified water content are very limited (practically non-existent), if 1) the habit

  14. A study of the pneumatic conveying of non-spherical particles in a turbulent horizontal channel flow

    Directory of Open Access Journals (Sweden)

    S. Laín

    2007-12-01

    Full Text Available In this work, the pneumatic conveying of non-spherical isometric particles with different degrees of non-sphericity is studied. The solids mass loading fraction is small enough in order to have a dilute flow, so inter-particle collisions can be neglected. As a first approximation, only the aerodynamic drag force acting on the particles is considered, neglecting the lift forces and the particle rotation. The drag coefficient is calculated using the correlations of Haider and Levenspiel (1989 and Ganser (1993. The numerical simulations are compared with experimental data in a narrow six meters long horizontal channel flow laden with quartz and duroplastic particles with mean diameters of 185 and 240 mu m, respectively (Kussin, 2004.

  15. The Acceleration of Charged Particles at a Spherical Shock Moving through an Irregular Magnetic Field

    Science.gov (United States)

    Giacalone, J.

    2017-10-01

    We investigate the physics of charged-particle acceleration at spherical shocks moving into a uniform plasma containing a turbulent magnetic field with a uniform mean. This has applications to particle acceleration at astrophysical shocks, most notably, to supernovae blast waves. We numerically integrate the equations of motion of a large number of test protons moving under the influence of electric and magnetic fields determined from a kinematically defined plasma flow associated with a radially propagating blast wave. Distribution functions are determined from the positions and velocities of the protons. The unshocked plasma contains a magnetic field with a uniform mean and an irregular component having a Kolmogorov-like power spectrum. The field inside the blast wave is determined from Maxwell’s equations. The angle between the average magnetic field and unit normal to the shock varies with position along its surface. It is quasi-perpendicular to the unit normal near the sphere’s equator, and quasi-parallel to it near the poles. We find that the highest intensities of particles, accelerated by the shock, are at the poles of the blast wave. The particles “collect” at the poles as they approximately adhere to magnetic field lines that move poleward from their initial encounter with the shock at the equator, as the shock expands. The field lines at the poles have been connected to the shock the longest. We also find that the highest-energy protons are initially accelerated near the equator or near the quasi-perpendicular portion of the shock, where the acceleration is more rapid.

  16. Particle acceleration during merging-compression plasma start-up in the Mega Amp Spherical Tokamak

    Science.gov (United States)

    McClements, K. G.; Allen, J. O.; Chapman, S. C.; Dendy, R. O.; Irvine, S. W. A.; Marshall, O.; Robb, D.; Turnyanskiy, M.; Vann, R. G. L.

    2018-02-01

    Magnetic reconnection occurred during merging-compression plasma start-up in the Mega Amp Spherical Tokamak (MAST), resulting in the prompt acceleration of substantial numbers of ions and electrons to highly suprathermal energies. Accelerated field-aligned ions (deuterons and protons) were detected using a neutral particle analyser at energies up to about 20 keV during merging in early MAST pulses, while nonthermal electrons have been detected indirectly in more recent pulses through microwave bursts. However no increase in soft x-ray emission was observed until later in the merging phase, by which time strong electron heating had been detected through Thomson scattering measurements. A test-particle code CUEBIT is used to model ion acceleration in the presence of an inductive toroidal electric field with a prescribed spatial profile and temporal evolution based on Hall-MHD simulations of the merging process. The simulations yield particle distributions with properties similar to those observed experimentally, including strong field alignment of the fast ions and the acceleration of protons to higher energies than deuterons. Particle-in-cell modelling of a plasma containing a dilute field-aligned suprathermal electron component suggests that at least some of the microwave bursts can be attributed to the anomalous Doppler instability driven by anisotropic fast electrons, which do not produce measurable enhancements in soft x-ray emission either because they are insufficiently energetic or because the nonthermal bremsstrahlung emissivity during this phase of the pulse is below the detection threshold. There is no evidence of runaway electron acceleration during merging, possibly due to the presence of three-dimensional field perturbations.

  17. Simulation of filtration processes in deformable media Part 3.1: Basic concepts and particle-fluid force implementation of a non-spherical dirt particle solver

    Directory of Open Access Journals (Sweden)

    G Boiger

    2016-04-01

    Full Text Available A Lagrangian solver to realistically model large, non-spherical dirt particlesand their behaviour in the vicinity of deformable filtration fibres has beenprogrammed. While this paper focuses on basic solver concepts as well asdrag force implementations, a related article, concerning the realisation ofinteraction effects and result verification, is forthcoming, [3].Within the framework of a digitally reconstructed, deformable filter fibregeometry, the solver traces the governing multi physics effects down to theoccurrence of single force- and torque vectors. In order to go from an initial,spherical particle model [2], to a more sophisticated, non-spherical model,the capabilities of a Six Degrees of Freedom Solver have been included inthe programming. A panel model and the concept of satellite help points areused to handle particles that encompass several fluid calculation cells.An innovative drag force implementation allows the consideration ofrotational- and shear flow effects on particle motion. Results are evaluatedand compared to an analytical formulation.

  18. Hafnium carbamates and ureates: new class of precursors for low-temperature growth of HfO2 thin films.

    Science.gov (United States)

    Pothiraja, Ramasamy; Milanov, Andrian P; Barreca, Davide; Gasparotto, Alberto; Becker, Hans-Werner; Winter, Manuela; Fischer, Roland A; Devi, Anjana

    2009-04-21

    Novel volatile compounds of hafnium, namely tetrakis-N,O-dialkylcarbamato hafnium(iv) [Hf((i)PrNC(O)O(i)Pr)(4)] () and tetrakis-N,N,N'-trialkylureato hafnium(iv) [Hf((i)PrNC(O)N-(Me)Et)(4)] (), have been synthesized through the simple insertion reaction of isopropyl isocyanate into hafnium isopropoxide and hafnium ethylmethylamide, respectively; based on the promising thermal properties, compound has been evaluated as a precursor for metalorganic chemical vapor deposition (MOCVD) of HfO(2) thin films, which resulted in the growth of stoichiometric and crystalline layers with a uniform morphology at temperature as low as 250 degrees C.

  19. Simulation study of HEMT structures with HfO2 cap layer for mitigating inverse piezoelectric effect related device failures

    Directory of Open Access Journals (Sweden)

    Deepthi Nagulapally

    2015-01-01

    Full Text Available The Inverse Piezoelectric Effect (IPE is thought to contribute to possible device failure of GaN High Electron Mobility Transistors (HEMTs. Here we focus on a simulation study to probe the possible mitigation of the IPE by reducing the internal electric fields and related elastic energy through the use of high-k materials. Inclusion of a HfO2 “cap layer” above the AlGaN barrier particularly with a partial mesa structure is shown to have potential advantages. Simulations reveal even greater reductions in the internal electric fields by using “field plates” in concert with high-k oxides.

  20. Electromagnetic interaction between a rising spherical particle in a conducting liquid and a localized magnetic field

    Science.gov (United States)

    Lyu, Z.; Tran, N.; Boeck, T.; Karcher, C.

    2017-07-01

    Lorentz force velocimetry (LFV) is a non-contact electromagnetic flow measurement technique for electrically conductive liquids. It is based on measuring the flow-induced force acting on an external permanent magnet. Motivated by extending LFV to liquid metal two-phase flow measurement, in a first test we consider the free rising of a non-conductive spherical particle in a thin tube of liquid metal (GaInSn) initially at rest. Here the measured force is due to the displacement flow induced by the rising particle. In this paper, numerical results are presented for three different analytical solutions of flows around a moving sphere under a localized magnetic field. This simplification is made since the hydrodynamic flow is difficult to measure or to compute. The Lorentz forces are compared to experiments. The aim of the present work is to check if our simple numerical model can provide Lorentz forces comparable to the experiments. The results show that the peak values of the Lorentz force from the analytical velocity fields provide us an upper limit to the measurement results. In the case of viscous flow around a moving sphere we recover the typical time-scale of Lorentz force signals.

  1. Optical levitation of a non-spherical particle in a loosely focused Gaussian beam.

    Science.gov (United States)

    Chang, Cheong Bong; Huang, Wei-Xi; Lee, Kyung Heon; Sung, Hyung Jin

    2012-10-08

    The optical force on a non-spherical particle subjected to a loosely focused laser beam was calculated using the dynamic ray tracing method. Ellipsoidal particles with different aspect ratios, inclination angles, and positions were modeled, and the effects of these parameters on the optical force were examined. The vertical component of the optical force parallel to the laser beam axis decreased as the aspect ratio decreased, whereas the ellipsoid with a small aspect ratio and a large inclination angle experienced a large vertical optical force. The ellipsoids were pulled toward or repelled away from the laser beam axis, depending on the inclination angle, and they experienced a torque near the focal point. The behavior of the ellipsoids in a viscous fluid was examined by analyzing a dynamic simulation based on the penalty immersed boundary method. As the ellipsoids levitated along the direction of the laser beam propagation, they moved horizontally with rotation. Except for the ellipsoid with a small aspect ratio and a zero inclination angle near the focal point, the ellipsoids rotated until the major axis aligned with the laser beam axis.

  2. Self-assembly in a model colloidal mixture of dimers and spherical particles.

    Science.gov (United States)

    Prestipino, Santi; Munaò, Gianmarco; Costa, Dino; Caccamo, Carlo

    2017-02-28

    We investigate the structure of a dilute mixture of amphiphilic dimers and spherical particles, a model relevant to the problem of encapsulating globular "guest" molecules in a dispersion. Dimers and spheres are taken to be hard particles, with an additional attraction between spheres and the smaller monomers in a dimer. Using the Monte Carlo simulation, we document the low-temperature formation of aggregates of guests (clusters) held together by dimers, whose typical size and shape depend on the guest concentration χ. For low χ (less than 10%), most guests are isolated and coated with a layer of dimers. As χ progressively increases, clusters grow in size becoming more and more elongated and polydisperse; after reaching a shallow maximum for χ≈50%, the size of clusters again reduces upon increasing χ further. In one case only (χ=50% and moderately low temperature) the mixture relaxed to a fluid of lamellae, suggesting that in this case clusters are metastable with respect to crystal-vapor separation. On heating, clusters shrink until eventually the system becomes homogeneous on all scales. On the other hand, as the mixture is made denser and denser at low temperature, clusters get increasingly larger until a percolating network is formed.

  3. Material parameters from frequency dispersion simulation of floating gate memory with Ge nanocrystals in HfO2

    Science.gov (United States)

    Palade, C.; Lepadatu, A. M.; Slav, A.; Lazanu, S.; Teodorescu, V. S.; Stoica, T.; Ciurea, M. L.

    2018-01-01

    Trilayer memory capacitors with Ge nanocrystals (NCs) floating gate in HfO2 were obtained by magnetron sputtering deposition on p-type Si substrate followed by rapid thermal annealing at relatively low temperature of 600 °C. The frequency dispersion of capacitance and resistance was measured in accumulation regime of Al/HfO2 gate oxide/Ge NCs in HfO2 floating gate/HfO2 tunnel oxide/SiOx/p-Si/Al memory capacitors. For simulation of the frequency dispersion a complex circuit model was used considering an equivalent parallel RC circuit for each layer of the trilayer structure. A series resistance due to metallic contacts and Si substrate was necessary to be included in the model. A very good fit to the experimental data was obtained and the parameters of each layer in the memory capacitor, i.e. capacitances and resistances were determined and in turn the intrinsic material parameters, i.e. dielectric constants and resistivities of layers were evaluated. The results are very important for the study and optimization of the hysteresis behaviour of floating gate memories based on NCs embedded in oxide.

  4. Influence of Poly (Ethylene Glycol) and Oleylamine on the Formation of Nano to Micron Size Spherical SiO2 Particles

    Science.gov (United States)

    We report an eco-friendly synthesis of well–controlled, nano-to-micron-size, spherical SiO2 particles using non-hazardous solvent and a byproducts-producing system. It was found that the morphology and size of spherical SiO2 particles are controlled by adjusting the concentration...

  5. Aluminium AA6061 Matrix Composite Reinforced with Spherical Alumina Particles Produced by Infiltration: Perspective on Aerospace Applications

    Directory of Open Access Journals (Sweden)

    Claudio Bacciarini

    2014-01-01

    Full Text Available Metal matrix composites, based on AA6061 reinforced with 60 vol% Al2O3 spherical particles, were produced by gas pressure infiltration and characterized for hardness, impulse excitation modulus, tensile properties (at room temperature and at 250°C, and machining. It was experimentally demonstrated that the novel alumina powder used in the present work does not react with the liquid Mg-containing matrix during the infiltration process. The AA6061 matrix therefore retains its ability to be strengthened by precipitation heat treatment. The latter behaviour combined with the spherical particle shape confers the studied material higher strength and better machinability in comparison with similar composites produced using standard angular alumina particles. The overall features are promising for applications in the aerospace industry, where light and strong materials are required.

  6. Interaction of Gaussian beam with near-spherical particle: an analytic-numerical approach for assessing scattering and stresses.

    Science.gov (United States)

    Boyde, Lars; Chalut, Kevin J; Guck, Jochen

    2009-08-01

    We derive a straightforward theoretical method to determine the electromagnetic fields for the incidence of a monochromatic laser beam on a near-spherical dielectric particle. The beam-shape coefficients are obtained from the radial laser fields and expressed as a finite series in a form that has, to our knowledge, not been published before. Our perturbation approach to solve Maxwell's equations in spherical coordinates employs two alternative techniques to match the boundary conditions: an analytic approach for small particles with low eccentricity and an adapted point-matching method for larger spheroids with higher aspect ratios. We present results for the internal and external fields, scattering intensities, and stresses exerted on the particle. While similarly accurate as others, our approach is easily implemented numerically and thus particularly useful in praxis, e.g., for analyzing optical traps, such as the optical stretcher.

  7. High performance organic nonvolatile memory transistors based on HfO2 and poly(α-methylstyrene) electret hybrid charge-trapping layers

    Science.gov (United States)

    Xu, W. C.; He, H. X.; Jing, X. S.; Wu, S. J.; Zhang, Z.; Gao, J. W.; Gao, X. S.; Zhou, G. F.; Lu, X. B.; Liu, J.-M.

    2017-08-01

    In this work, we fabricated a high performance flash-type organic nonvolatile memory transistor, which adopted polymer-electret poly(α-methylstyrene) (PαMS) and HfO2 films as hybrid charge trapping layer (CTL). Compared with a single HfO2 or PαMS CTL structure, the hybrid HfO2/PαMS CTL structure can provide enhanced charge trapping efficiency to increase the device operation speed and reduce the leakage current to boost the device reliability. The fabricated nonvolatile organic memory transistors with the hybrid CTL shows excellent electrical properties, including low operation voltage (8 V), high speed (retention (on-off current ratio of 2.6 × 104 after 104 s), and good endurance (more than 2000 program/erase cycles). The present work provides useful idea for the design of future low-power consumption and highly reliable organic nonvolatile memories.

  8. The Development of HfO2-Rare Earth Based Oxide Materials and Barrier Coatings for Thermal Protection Systems

    Science.gov (United States)

    Zhu, Dongming; Harder, Bryan James

    2014-01-01

    Advanced hafnia-rare earth oxides, rare earth aluminates and silicates have been developed for thermal environmental barrier systems for aerospace propulsion engine and thermal protection applications. The high temperature stability, low thermal conductivity, excellent oxidation resistance and mechanical properties of these oxide material systems make them attractive and potentially viable for thermal protection systems. This paper will focus on the development of the high performance and high temperature capable ZrO2HfO2-rare earth based alloy and compound oxide materials, processed as protective coating systems using state-or-the-art processing techniques. The emphasis has been in particular placed on assessing their temperature capability, stability and suitability for advanced space vehicle entry thermal protection systems. Fundamental thermophysical and thermomechanical properties of the material systems have been investigated at high temperatures. Laser high-heat-flux testing has also been developed to validate the material systems, and demonstrating durability under space entry high heat flux conditions.

  9. The Melting of Spherical Ice Particles Falling at Terminal Velocity in Air: AN Experimental and Theoretical Study.

    Science.gov (United States)

    Rasmussen, Roy Martin

    This study utilized the UCLA cloud physics wind tunnel and the IBM 3033 computer. The wind tunnel experiments were conducted using two separate procedures, depending on the size of the spherical particle. Particles less than 1 mm diameter, were melted in free fall while experiencing a time varying environmental temperature, similar to the variation of temperature it would encounter while freely falling in the atmosphere. Particles larger than 1 mm diameter have a tendency to wander towards the tunnel walls, requiring restraint by a thin nylon fiber frozen halfway through the particle. Using this fiber, the particle was suspended from above. Although attached to a thread, the particle's terminal velocity was constantly maintained during melting by keeping the fiber slack. Particles less than 1 mm diameter usually undergo "sailing" motions upon melting due to the melting of surface protuberances. Once the protuberances are melted, the particle falls with no horizontal drift. The melting ice core was observed to remain tangent with the downstream end of the particle, resulting in an eccentric melting location. The meltwater itself was also observed to circulate due to the external shear of the air on the meltwater surface. For these small particles, no meltwater was shed. Particles larger than 9 mm diameter were found to shed meltwater, with the fraction shed increasing with particle size. Particles between 9 mm and 5 mm diameter did not shed their meltwater, and did not develop an internal circulation. Particles between 1 mm and 5 mm, however, did develop a significant internal circulation, resulting in a conically shaped ice core. For each of the above size ranges, melting theories are developed which are able to quantitatively describe the melting rates of these particles.

  10. Corrosion Protection of Copper Using Al2O3, TiO2, ZnO, HfO2, and ZrO2Atomic Layer Deposition.

    Science.gov (United States)

    Daubert, James S; Hill, Grant T; Gotsch, Hannah N; Gremaud, Antoine P; Ovental, Jennifer S; Williams, Philip S; Oldham, Christopher J; Parsons, Gregory N

    2017-02-01

    Atomic layer deposition (ALD) is a viable means to add corrosion protection to copper metal. Ultrathin films of Al 2 O 3 , TiO 2 , ZnO, HfO 2 , and ZrO 2 were deposited on copper metal using ALD, and their corrosion protection properties were measured using electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV). Analysis of ∼50 nm thick films of each metal oxide demonstrated low electrochemical porosity and provided enhanced corrosion protection from aqueous NaCl solution. The surface pretreatment and roughness was found to affect the extent of the corrosion protection. Films of Al 2 O 3 or HfO 2 provided the highest level of initial corrosion protection, but films of HfO 2 exhibited the best coating quality after extended exposure. This is the first reported instance of using ultrathin films of HfO 2 or ZrO 2 produced with ALD for corrosion protection, and both are promising materials for corrosion protection.

  11. Fabrication of HfO2 patterns by laser interference nanolithography and selective dry etching for III-V CMOS application

    Directory of Open Access Journals (Sweden)

    Molina-Aldareguia Jon

    2011-01-01

    Full Text Available Abstract Nanostructuring of ultrathin HfO2 films deposited on GaAs (001 substrates by high-resolution Lloyd's mirror laser interference nanolithography is described. Pattern transfer to the HfO2 film was carried out by reactive ion beam etching using CF4 and O2 plasmas. A combination of atomic force microscopy, high-resolution scanning electron microscopy, high-resolution transmission electron microscopy, and energy-dispersive X-ray spectroscopy microanalysis was used to characterise the various etching steps of the process and the resulting HfO2/GaAs pattern morphology, structure, and chemical composition. We show that the patterning process can be applied to fabricate uniform arrays of HfO2 mesa stripes with tapered sidewalls and linewidths of 100 nm. The exposed GaAs trenches were found to be residue-free and atomically smooth with a root-mean-square line roughness of 0.18 nm after plasma etching. PACS: Dielectric oxides 77.84.Bw, Nanoscale pattern formation 81.16.Rf, Plasma etching 52.77.Bn, Fabrication of III-V semiconductors 81.05.Ea

  12. Experimental Investigation of the Effect of Spherical Particle Size Distribution on Frictional Pressure drop in Particulate Debris Bed

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jin Ho; Kim, Eunho; Park, Hyun Sun [POSTECH, Daejeon (Korea, Republic of)

    2015-10-15

    It is important to ensure the coolant ingression into the internally heat generated debris bed which is governed by pressure drop in debris bed to assure the long-term cooling of debris bed on the cavity floor. For this reason, it is necessary to understand the pressure drop mechanism in porous bed that can be characterized by physical parameters that include porosity, particle morphology, particle size distribution etc. According to previous investigations on molten fuel coolant interaction (FCI) experiment, the settled particulate debris bed after fuel-coolant interaction were stratified and it was composed of multi-sized particles with irregular shape. (Karbojian et al., 2009; Magallon, 2006). Among these characteristics of debris bed, this study focused on the effect of particle size distribution on frictional pressure drop in bed. The experiment using single-phase water was conducted to investigate the effect of spherical particle size distribution on frictional pressure drop in mixed bed. This study reports the experimental data for measured frictional pressure drops in bed according to the particle Reynolds number. It is composed of multi-sized spherical particles whose sizes are varied from 1 mm to 10 mm. Besides, the experimental data is compared to the Ergun equation with the mean particle diameters (mass, area, length, and number mean diameters). The results of this study are also compared to those of KTH published in 2011. The conclusions are summarized as follows. The calculated mean particle diameters can be changed according to chosen particle sizes and those mass fractions even though the cumulative mass fractions are almost similar trend. As results of obtaining the effective diameter in mixed using measured frictional pressure drops and the Ergun equation, it is close to the length mean diameter when the particle Reynolds number is lower than 7, however, it has the value between the length mean diameter and the area mean diameter when the particle

  13. Origin of non-spherical particles in the boundary layer over Beijing, China: based on balloon-borne observations.

    Science.gov (United States)

    Chen, Bin; Yamada, Maromu; Iwasaka, Yasunobu; Zhang, Daizhou; Wang, Hong; Wang, Zhenzhu; Lei, Hengchi; Shi, Guangyu

    2015-10-01

    Vertical structures of aerosols from the ground to about 1,000 m altitude in Beijing were measured with a balloon-borne optical particle counter. The results showed that, in hazy days, there were inversions at approximately 500-600 m, below which the particulate matters were well mixed vertically, while the concentration of particles decreased sharply above the mixing layer. Electron microscopic observation of the particles collected with the balloon-borne impactor indicates that the composition of particles is different according to weather conditions in the boundary mixing layer of Beijing city and suggests that dust particles are always dominant in coarse-mode particles. Interestingly, sea-salt particles are frequently identified, suggesting the importance of marine air inflow to the Beijing area even in summer. The Ca-rich spherical particles are also frequently identified, suggesting chemical modification of dust particle by NOx or emission of CaO and others from local emission. Additionally, those types of particles showed higher concentration above the mixing layer under the relatively calm weather condition of summer, suggesting the importance of local-scale convection found in summer which rapidly transported anthropogenic particles above the mixing layer. Lidar extinction profiles qualitatively have good consistency with the balloon-borne measurements. Attenuation effects of laser pulse intensity are frequently observed due to high concentration of particulate matter in the Beijing atmosphere, and therefore quantitative agreement of lidar return and aerosol concentration can be hardly observed during dusty condition. Comparing the depolarization ratio obtained from the lidar measurements with the balloon-borne measurements, the contribution of the dry sea-salt particles, in addition to the dust particles, is suggested as an important factor causing depolarization ratio in the Beijing atmosphere.

  14. In-situ growth of HfO2 on clean 2H-MoS2 surface: Growth mode, interface reactions and energy band alignment

    Science.gov (United States)

    Chen, Chang Pang; Ong, Bin Leong; Ong, Sheau Wei; Ong, Weijie; Tan, Hui Ru; Chai, Jian Wei; Zhang, Zheng; Wang, Shi Jie; Pan, Ji Sheng; Harrison, Leslie John; Kang, Hway Chuan; Tok, Eng Soon

    2017-10-01

    Room temperature growth of HfO2 thin film on clean 2H-MoS2 via plasma-sputtering of Hf-metal target in an argon/oxygen environment was studied in-situ using x-ray photoelectron spectroscopy (XPS). The deposited film was observed to grow akin to a layer-by-layer growth mode. At the onset of growth, a mixture of sulfate- and sulfite-like species (SOx2- where x = 3, 4), and molybdenum trioxide (MoO3), are formed at the HfO2/MoS2 interface. An initial decrease in binding energies for both Mo 3d and S 2p core-levels of the MoS2 substrate by 0.4 eV was also observed. Their binding energies, however, did not change further with increasing HfO2 thickness. There was no observable change in the Hf4f core-level binding energy throughout the deposition process. With increasing HfO2 deposition, MoO3 becomes buried at the interface while SOx2- was observed to be present in the film. The shift of 0.4 eV for both Mo 3d and S 2p core-levels of the MoS2 substrate can be attributed to a charge transfer from the substrate to the MoO3/SOx2--like interface layer. Consequently, the Type I heterojunction valence band offset (conduction band offset) becomes 1.7 eV (2.9 eV) instead of 1.3 eV (3.3 eV) expected from considering the bulk HfO2 and MoS2 valence band offset (conduction band offset). The formation of these states and its influence on band offsets will need to be considered in their device applications.

  15. Investigation of various properties of HfO2-TiO2 thin film composites deposited by multi-magnetron sputtering system

    Science.gov (United States)

    Mazur, M.; Poniedziałek, A.; Kaczmarek, D.; Wojcieszak, D.; Domaradzki, J.; Gibson, D.

    2017-11-01

    In this work the properties of hafnium dioxide (HfO2), titanium dioxide (TiO2) and mixed HfO2-TiO2 thin films with various amount of titanium addition, deposited by magnetron sputtering were described. Structural, surface, optical and mechanical properties of deposited coatings were analyzed. Based on X-ray diffraction and Raman scattering measuremets it was observed that there was a significant influence of titanium concentration in mixed TiO2-HfO2 thin films on their microstructure. Increase of Ti content in prepared mixed oxides coatings caused, e.g. a decrease of average crystallite size and amorphisation of the coatings. As-deposited hafnia and titania thin films exhibited nanocrystalline structure of monoclinic phase and mixed anatase-rutile phase for HfO2 and TiO2 thin films, respectively. Atomic force microscopy investigations showed that the surface of deposited thin films was densely packed, crack-free and composed of visible grains. Surface roughness and the value of water contact angle decreased with the increase of Ti content in mixed oxides. Results of optical studies showed that all deposited thin films were well transparent in a visible light range. The effect of the change of material composition on the cut-off wavelength, refractive index and packing density was also investigated. Performed measurements of mechanical properties revealed that hardness and Young's elastic modulus of thin films were dependent on material composition. Hardness of thin films increased with an increase of Ti content in thin films, from 4.90 GPa to 13.7 GPa for HfO2 and TiO2, respectively. The results of the scratch resistance showed that thin films with proper material composition can be used as protective coatings in optical devices.

  16. Application of Convolution Perfectly Matched Layer in MRTD scattering model for non-spherical aerosol particles and its performance analysis

    Science.gov (United States)

    Hu, Shuai; Gao, Taichang; Li, Hao; Yang, Bo; Jiang, Zidong; Liu, Lei; Chen, Ming

    2017-10-01

    The performance of absorbing boundary condition (ABC) is an important factor influencing the simulation accuracy of MRTD (Multi-Resolution Time-Domain) scattering model for non-spherical aerosol particles. To this end, the Convolution Perfectly Matched Layer (CPML), an excellent ABC in FDTD scheme, is generalized and applied to the MRTD scattering model developed by our team. In this model, the time domain is discretized by exponential differential scheme, and the discretization of space domain is implemented by Galerkin principle. To evaluate the performance of CPML, its simulation results are compared with those of BPML (Berenger's Perfectly Matched Layer) and ADE-PML (Perfectly Matched Layer with Auxiliary Differential Equation) for spherical and non-spherical particles, and their simulation errors are analyzed as well. The simulation results show that, for scattering phase matrices, the performance of CPML is better than that of BPML; the computational accuracy of CPML is comparable to that of ADE-PML on the whole, but at scattering angles where phase matrix elements fluctuate sharply, the performance of CPML is slightly better than that of ADE-PML. After orientation averaging process, the differences among the results of different ABCs are reduced to some extent. It also can be found that ABCs have a much weaker influence on integral scattering parameters (such as extinction and absorption efficiencies) than scattering phase matrices, this phenomenon can be explained by the error averaging process in the numerical volume integration.

  17. An analytical investigation on unsteady motion of vertically falling spherical particles in non-Newtonian fluid by Collocation Method

    Directory of Open Access Journals (Sweden)

    M. Rahimi-Gorji

    2015-06-01

    Full Text Available An analytical investigation is applied for unsteady motion of a rigid spherical particle in a quiescent shear-thinning power-law fluid. The results were compared with those obtained from Collocation Method (CM and the established Numerical Method (Fourth order Runge–Kutta scheme. It was shown that CM gave accurate results. Collocation Method (CM and Numerical Method are used to solve the present problem. We obtained that the CM which was used to solve such nonlinear differential equation with fractional power is simpler and more accurate than series method such as HPM which was used in some previous works by others but the new method named Akbari-Ganji’s Method (AGM is an accurate and simple method which is slower than CM for solving such problems. The terminal settling velocity—that is the velocity at which the net forces on a falling particle eliminate—for three different spherical particles (made of plastic, glass and steel and three flow behavior index n, in three sets of power-law non-Newtonian fluids was investigated, based on polynomial solution (CM. Analytical results obtained indicated that the time of reaching the terminal velocity in a falling procedure is significantly increased with growing of the particle size that validated with Numerical Method. Further, with approaching flow behavior to Newtonian behavior from shear-thinning properties of flow (n → 1, the transient time to achieving the terminal settling velocity is decreased.

  18. The influence of silicon substitution on the properties of spherical- and whisker-like biphasic α-calcium-phosphate/hydroxyapatite particles.

    Science.gov (United States)

    Jokic, B; Mitric, M; Popovic, M; Sima, L; Petrescu, S M; Petrovic, R; Janackovic, Dj

    2011-10-01

    In this work, the influence of the morphology of hydroxyapatite particles on silicon substitution through hydrothermal synthesis performed under the same conditions was investigated. Spherical- and whisker-like hydroxyapatite particles were obtained starting from calcium-nitrate, sodium dihydrogen phosphate, disodium-ethylenediaminetetraacetic acid and urea (used only for the synthesis of whisker-like particles) dissolved in aqueous solutions. Silicon was introduced into the solution using tetraethylorthosilicate. X-ray diffraction, infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy and transmission electron microscopy indicate that silicon doping induce different phase compositions and bioactivity of spherical- and whisker-like hydroxyapatite particles obtained under the same hydrothermal conditions. Silicon-substituted, spherical hydroxyapatites particles showed greater phase transformation to silicon-substituted α- calcium-phosphate compared with whiskers-like hydroxyapatite particles synthesized with the same amount of added silicon. Metabolic activity assay performed with SaOs2 osteosarcoma cells showed better biocompatibility of annealed biphasic spherical-like particles compared with annealed whiskerlike particles while dried spherical-like particles induce high cytotoxicity effect.

  19. Green synthesis of zinc oxide nano-sized spherical particles using Terminalia chebula fruits extract for their photocatalytic applications

    Science.gov (United States)

    Rana, N.; Chand, Subhash; Gathania, Arvind K.

    2016-01-01

    The present study describes the green synthesis of ZnO nano-sized spherical particles (ZnO-NPs) using aqueous fruits extract of Terminalia chebula. The Structural, morphological and optical properties of green-synthesized ZnO-NPs are characterized by X-ray diffraction, Fourier transform infrared, field emission-scanning electron microscope, ultraviolet-visible and photoluminescence spectroscopy techniques. The results show that the synthesized nanoparticles have stable hexagonal wurtzite structure, and roughly spherical in shape. To explore the photocatalytic activity of the ZnO-NPs the photocatalytic degradation of rhodamine B (RhB) dye is investigated. The results reveal that ZnO-NPs prepared through green synthesis route are found to be efficient in the degradation of RhB dye.

  20. A proposal on alternative sampling-based modeling method of spherical particles in stochastic media for Monte Carlo simulation

    Directory of Open Access Journals (Sweden)

    Song Hyun Kim

    2015-08-01

    Full Text Available Chord length sampling method in Monte Carlo simulations is a method used to model spherical particles with random sampling technique in a stochastic media. It has received attention due to the high calculation efficiency as well as user convenience; however, a technical issue regarding boundary effect has been noted. In this study, after analyzing the distribution characteristics of spherical particles using an explicit method, an alternative chord length sampling method is proposed. In addition, for modeling in finite media, a correction method of the boundary effect is proposed. Using the proposed method, sample probability distributions and relative errors were estimated and compared with those calculated by the explicit method. The results show that the reconstruction ability and modeling accuracy of the particle probability distribution with the proposed method were considerably high. Also, from the local packing fraction results, the proposed method can successfully solve the boundary effect problem. It is expected that the proposed method can contribute to the increasing of the modeling accuracy in stochastic media.

  1. Spherical carbon particles and carbon nanotubes prepared by autogenic reactions : evaluation as anodes in lithium electrochemical cells.

    Energy Technology Data Exchange (ETDEWEB)

    Pol, V. G.; Thackeray, M. M. (Chemical Sciences and Engineering Division)

    2011-05-01

    Autogenic reactions, based on the decomposition of one or more precursors at elevated temperatures with self generated pressures can be used to prepare a wide range of materials with interesting structural, morphological and technological properties. Recent reports that spherical carbon particles and carbon nanotubes can be prepared by this technique from waste products, such as used plastic bags, have highlighted this environmentally-attractive approach to synthesize new or modified carbon-based materials. In this paper, we report the synthesis of spherical carbon particles and carbon nanotubes and their evaluation as negative electrodes (anodes) in lithium electrochemical cells. A steady reversible capacity of approximately 240 mAh/g for hundreds of cycles was achieved from both types of carbon, when cycled at a 1C rate between 1.5 V and 5 mV. A reversible capacity of 372 mAh/g, i.e., the theoretical value for graphite, was obtained from the carbon nanotube electrodes by raising the upper voltage limit to 3 V. To increase the graphitic order in the carbon spheres, the particles were heated to 2400 C in an inert atmosphere. This treatment reduced the first cycle irreversible capacity loss of Li/C half cells from 60 to 20%, the spherical carbon electrodes yielding a stable 252 mAh/g discharge capacity for numerous cycles. Structural and morphological information about the parent and cycled carbon electrodes, obtained by powder X-ray diffraction, Raman spectroscopy, high-resolution scanning electron microscopy, and electron dispersive analysis of X-rays is provided.

  2. Spherical Carbon Particles and Carbon Nanotubes Prepared by Autogenic Reactions: Evaluation as Anodes in Lithium Electrochemical Cells

    Energy Technology Data Exchange (ETDEWEB)

    Pol, Vilas G.; Thackeray, Michael

    2010-01-01

    Autogenic reactions, based on the decomposition of one or more precursors at elevated temperatures with self generated pressures can be used to prepare a wide range of materials with interesting structural, morphological and technological properties. Recent reports that spherical carbon particles and carbon nanotubes can be prepared by this technique from waste products, such as used plastic bags, have highlighted this environmentally-attractive approach to synthesize new or modified carbon-based materials. In this paper, we report the synthesis of spherical carbon particles and carbon nanotubes and their evaluation as negative electrodes (anodes) in lithium electrochemical cells. A steady reversible capacity of approximately 240 mAh/g for hundreds of cycles was achieved from both types of carbon, when cycled at a 1C rate between 1.5 V and 5 mV. A reversible capacity of 372 mAh/g, i.e., the theoretical value for graphite, was obtained from the carbon nanotube electrodes by raising the upper voltage limit to 3 V. To increase the graphitic order in the carbon spheres, the particles were heated to 2400 °C in an inert atmosphere. This treatment reduced the first cycle irreversible capacity loss of Li/C half cells from 60 to 20%, the spherical carbon electrodes yielding a stable 252 mAh/g discharge capacity for numerous cycles. Structural and morphological information about the parent and cycled carbon electrodes, obtained by powder X-ray diffraction, Raman spectroscopy, high-resolution scanning electron microscopy, and electron dispersive analysis of X-rays is provided.

  3. Electrical characteristics of multilayered HfO2-Al2O3 charge trapping stacks deposited by ALD

    Science.gov (United States)

    Spassov, D.; Paskaleva, A.; Guziewicz, E.; Luka, G.; AKrajewski, T.; Kopalko, K.; Wierzbicka, A.; Blagoev, B.

    2016-10-01

    Electrical and charge trapping properties of atomic layer deposited HfO2-Al2O3 multilayer stacks with two different Al2O3 sublayer thicknesses were investigated regarding their implementation in charge trapping non-volatile memories. The effect of post deposition annealing in oxygen at 600°C is also studied. The decreasing Al2O3 thickness increases the stack's dielectric constant and the density of the initial positive oxide charge. The initial oxide charge increases after annealing to ∼6×1012 cm-2 and changes its sign to negative for the stacks with thicker Al2O3. The annealing enhances the dielectric constant of the stacks and reduces their thickness preserving the amorphous status. Nevertheless the annealing is not beneficial for the stacks with thicker Al2O3 as it considerably increases leakage currents. Conduction mechanisms in stacks were considered in terms of hopping conduction at low electric fields, and Fowler- Nordheim tunnelling, Schottky emission and Poole-Frenkel effect at higher ones. Maximum memory windows of about 12 and 16V were obtained for the as-grown structures with higher and lower Al2O3 content, respectively. In latter case additional improvement (the memory window increase up to 23V) is achieved by the annealing.

  4. Wide band antireflective coatings Al2O3 / HfO2 / MgF2 for UV region

    Science.gov (United States)

    Winkowski, P.; Marszałek, Konstanty W.

    2013-07-01

    Deposition technology of the three layers antireflective coatings consists of hafnium compound are presented in this paper. Oxide films were deposited by means of e-gun evaporation in vacuum of 5x10-5 mbar in presence of oxygen and fluoride films by thermal evaporation. Substrate temperature was 250°C. Coatings were deposited onto optical lenses made from quartz glass (Corning HPFS). Thickness and deposition rate were controlled by thickness measuring system Inficon XTC/2. Simulations leading to optimization of thickness and experimental results of optical measurements carried during and after deposition process were presented. Physical thickness measurements were made during deposition process and were equal to 43 nm/74 nm/51 nm for Al2O3 / HfO2 / MgF2 respectively. Optimization was carried out for ultraviolet region from 230nm to the beginning of visible region 400 nm. In this region the average reflectance of the antireflective coating was less than 0.5% in the whole range of application.

  5. Single vacancy defect spectroscopy on HfO2 using random telegraph noise signals from scanning tunneling microscopy

    Science.gov (United States)

    Thamankar, R.; Raghavan, N.; Molina, J.; Puglisi, F. M.; O'Shea, S. J.; Shubhakar, K.; Larcher, L.; Pavan, P.; Padovani, A.; Pey, K. L.

    2016-02-01

    Random telegraph noise (RTN) measurements are typically carried out at the device level using standard probe station based electrical characterization setup, where the measured current represents a cumulative effect of the simultaneous response of electron capture/emission events at multiple oxygen vacancy defect (trap) sites. To better characterize the individual defects in the high-κ dielectric thin film, we propose and demonstrate here the measurement and analysis of RTN at the nanoscale using a room temperature scanning tunneling microscope setup, with an effective area of interaction of the probe tip that is as small as 10 nm in diameter. Two-level and multi-level RTN signals due to single and multiple defect locations (possibly dispersed in space and energy) are observed on 4 nm HfO2 thin films deposited on n-Si (100) substrate. The RTN signals are statistically analyzed using the Factorial Hidden Markov Model technique to decode the noise contribution of more than one defect (if any) and estimate the statistical parameters of each RTN signal (i.e., amplitude of fluctuation, capture and emission time constants). Observation of RTN at the nanoscale presents a new opportunity for studies on defect chemistry, single-defect kinetics and their stochastics in thin film dielectric materials. This method allows us to characterize the fast traps with time constants ranging in the millisecond to tens of seconds range.

  6. The rotation and translation of non-spherical particles in homogeneous isotropic turbulence

    Science.gov (United States)

    Byron, Margaret

    The motion of particles suspended in environmental turbulence is relevant to many scientific fields, from sediment transport to biological interactions to underwater robotics. At very small scales and simple shapes, we are able to completely mathematically describe the motion of inertial particles; however, the motion of large aspherical particles is significantly more complex, and current computational models are inadequate for large or highly-resolved domains. Therefore, we seek to experimentally investigate the coupling between freely suspended particles and ambient turbulence. A better understanding of this coupling will inform not only engineering and physics, but the interactions between small aquatic organisms and their environments. In the following pages, we explore the roles of shape and buoyancy on the motion of passive particles in turbulence, and allow these particles to serve as models for meso-scale aquatic organisms. We fabricate cylindrical and spheroidal particles and suspend them in homogeneous, isotropic turbulence that is generated via randomly-actuated jet arrays. The particles are fabricated with agarose hydrogel, which is refractive-index-matched to the surrounding fluid (water). Both the fluid and the particle are seeded with passive tracers, allowing us to perform Particle Image Velocimetry (PIV) simultaneously on the particle and fluid phase. To investigate the effects of shape, particles are fabricated at varying aspect ratios; to investigate the effects of buoyancy, particles are fabricated at varying specific gravities. Each particle type is freely suspended at a volume fraction of F=0.1%, for which four-way coupling interactions are negligible. The suspended particles are imaged together with the surrounding fluid and analyzed using stereoscopic PIV, which yields three velocity components in a two-dimensional measurement plane. Using image thresholding, the results are separated into simultaneous fluid-phase and solid-phase velocity

  7. The rotation and translation of non-spherical particles in homogeneous isotropic turbulence

    CERN Document Server

    Byron, Margaret L

    2015-01-01

    The motion of particles suspended in environmental turbulence is relevant to many scientific fields, from sediment transport to biological interactions to underwater robotics. At very small scales and simple shapes, we are able to completely mathematically describe the motion of inertial particles; however, the motion of large aspherical particles is significantly more complex, and current computational models are inadequate for large or highly-resolved domains. Therefore, we seek to experimentally investigate the coupling between freely suspended particles and ambient turbulence. A better understanding of this coupling will inform not only engineering and physics, but the interactions between small aquatic organisms and their environments. We explore the roles of shape and buoyancy on the motion of passive particles in turbulence, and allow these particles to serve as models for meso-scale aquatic organisms. The results of this study will allow us to more accurately predict the motion of aspherical particles...

  8. Motion of a Free-Settling Spherical Particle Driven by a Laser-Induced Bubble.

    Science.gov (United States)

    Wu, Shengji; Zuo, Zhigang; Stone, Howard A; Liu, Shuhong

    2017-08-25

    We document experimentally four different interactions of a laser-induced bubble and a free-settling particle, with different combinations of the geometric and physical parameters of the system. Our force balance model shows that four nondimensional factors involving the particle radius a, the maximum bubble radius R_{max}, the initial separation distance l_{0} between the particle center and the bubble center, the fluid viscosity μ_{f}, and the particle and fluid densities ρ_{p} and ρ_{f}, respectively, in detail l_{0}/R_{max}, a/R_{max}, ρ_{p}/ρ_{f}, and μ^{*}=μ_{f}T_{c}/ρ_{f}R_{max}^{2}, where T_{c}=0.915R_{max}sqrt[ρ_{f}/(p_{∞}-p_{v})], influence the particle-bubble dynamics, and reasonably predict the maximum particle velocity and the limiting condition when the particle starts to "bounce off" the bubble during bubble growth. In particular, we also discover the high-speed ejection of the particle, and a cavity behind the particle, in cases when initially the particle is in very close proximity to the bubble. These observations offer new insights into the causal mechanism for the enhanced cavitation erosion in silt-laden water.

  9. The structural, magnetic and microwave properties of spherical and flake shaped carbonyl iron particles as thin multilayer microwave absorbers

    Science.gov (United States)

    Khani, Omid; Shoushtari, Morteza Zargar; Ackland, Karl; Stamenov, Plamen

    2017-04-01

    An increase in microwave permeability is a prerequisite for reducing the thickness of radar absorber coatings. The aim of this paper is to increase the magnetic loss of commercial carbonyl iron particles for fabricating wideband microwave absorbers with a multilayer structure. For this purpose, carbonyl iron particles were milled and their static and dynamic magnetic properties were studied before and after milling. A distinct morphological change from spherical to flake-like particles is measured with increased milling time, whereas no distinct changes in magnetic properties are measured with increased milling time. The imaginary part of the permeability (μ״) of the milled carbonyl iron particles increased from 1.23 to 1.88 and showed a very broad peak over the entire frequency range 1-18 GHz. The experimental results were modeled using the Rousselle effective medium theory (EMT) in the Neo formulation. The theoretical predictions showed good agreement with the experimental results. Two layer absorbers were designed according to the measured microwave parameters and the multilayer design. The results revealed that a thin multilayer with a thickness of 1.75 mm can effectively absorb microwaves in both the entire X and Ku frequency bands. The results suggest that microwave absorbers with excellent absorption properties could be mass-produced, using commercial carbonyl iron particles.

  10. Particle system based adaptive sampling on spherical parameter space to improve the MDL method for construction of statistical shape models.

    Science.gov (United States)

    Xu, Rui; Zhou, Xiangrong; Hirano, Yasushi; Tachibana, Rie; Hara, Takeshi; Kido, Shoji; Fujita, Hiroshi

    2013-01-01

    Minimum description length (MDL) based group-wise registration was a state-of-the-art method to determine the corresponding points of 3D shapes for the construction of statistical shape models (SSMs). However, it suffered from the problem that determined corresponding points did not uniformly spread on original shapes, since corresponding points were obtained by uniformly sampling the aligned shape on the parameterized space of unit sphere. We proposed a particle-system based method to obtain adaptive sampling positions on the unit sphere to resolve this problem. Here, a set of particles was placed on the unit sphere to construct a particle system whose energy was related to the distortions of parameterized meshes. By minimizing this energy, each particle was moved on the unit sphere. When the system became steady, particles were treated as vertices to build a spherical mesh, which was then relaxed to slightly adjust vertices to obtain optimal sampling-positions. We used 47 cases of (left and right) lungs and 50 cases of livers, (left and right) kidneys, and spleens for evaluations. Experiments showed that the proposed method was able to resolve the problem of the original MDL method, and the proposed method performed better in the generalization and specificity tests.

  11. Impact of Spherical Inclusion Mean Chord Length and Radius Distribution on Three-Dimensional Binary Stochastic Medium Particle Transport

    Energy Technology Data Exchange (ETDEWEB)

    Brantley, P S; Martos, J N

    2011-03-02

    We describe a parallel benchmark procedure and numerical results for a three-dimensional binary stochastic medium particle transport benchmark problem. The binary stochastic medium is composed of optically thick spherical inclusions distributed in an optically thin background matrix material. We investigate three sphere mean chord lengths, three distributions for the sphere radii (constant, uniform, and exponential), and six sphere volume fractions ranging from 0.05 to 0.3. For each sampled independent material realization, we solve the associated transport problem using the Mercury Monte Carlo particle transport code. We compare the ensemble-averaged benchmark fiducial tallies of reflection from and transmission through the spatial domain as well as absorption in the spherical inclusion and background matrix materials. For the parameter values investigated, we find a significant dependence of the ensemble-averaged fiducial tallies on both sphere mean chord length and sphere volume fraction, with the most dramatic variation occurring for the transmission through the spatial domain. We find a weaker dependence of most benchmark tally quantities on the distribution describing the sphere radii, provided the sphere mean chord length used is the same in the different distributions. The exponential distribution produces larger differences from the constant distribution than the uniform distribution produces. The transmission through the spatial domain does exhibit a significant variation when an exponential radius distribution is used.

  12. Clinical Long-Term Outcome and Reinterventional Rate After Uterine Fibroid Embolization with Nonspherical Versus Spherical Polyvinyl Alcohol Particles

    Energy Technology Data Exchange (ETDEWEB)

    Duvnjak, Stevo, E-mail: stevo.duvnjak@rsyd.dk [Odense University Hospital, Department of Radiology (Denmark); Ravn, Pernille [Odense University Hospital, Department of Gynecology (Denmark); Green, Anders [Odense University Hospital, Odense Patient Data Explorative Network (Denmark); Andersen, Poul Erik [Odense University Hospital, Department of Radiology (Denmark)

    2016-02-15

    PurposeThis study was designed to evaluate the long-term clinical outcome and frequency of reinterventions in patients with uterine fibroids treated with embolization at a single center using polyvinyl alcohol microparticles.MethodsThe study included all patients with symptomatic uterine fibroids treated with uterine fibroid embolization (UFE) with spherical (s-PVA) and nonspherical (ns-PVA) polyvinyl alcohol microparticles during the period January 2001 to January 2011. Clinical success and secondary interventions were examined. Hospital records were reviewed during follow-up, and symptom-specific questionnaires were sent to all patients.ResultsIn total, 515 patients were treated with UFE and 350 patients (67 %) were available for long-term clinical follow-up. Median time of follow-up was 93 (range 76–120.2) months. Eighty-five patients (72 %) had no reinterventions during follow-up in the group embolized with ns-PVA compared with 134 patients (58 %) treated with s-PVA. Thirty-three patients (28 %) underwent secondary interventions in the ns-PVA group compared with 98 patients (42 %) in s-PVA group (χ{sup 2} test, p < 0.01).ConclusionsSpherical PVA particles 500–700 µm showed high reintervention rate at long-term follow-up, and almost one quarter of the patients underwent secondary interventions, suggesting that this type of particle is inappropriate for UFE.

  13. Laminated CeO2/HfO2 High-K Gate Dielectrics Grown by Pulsed Laser Deposition in Reducing Ambient

    NARCIS (Netherlands)

    Karakaya, K.; Barcones Campo, B.; Zinine, A.; Rittersma, Z.M.; Graat, P.; van Berkum, J.G.M.; Verheijen, M.A.; Rijnders, Augustinus J.H.M.; Blank, David H.A.

    2006-01-01

    CeO2 and HfO2 dielectric layers were deposited in an Ar+(5%)H2 gas mixture by Pulsed Laser Deposition (PLD) on Si (100). A CeO2-Ce2O3 transformation is achieved by deposition in reducing ambient. It is also shown that in-situ post deposition anneal efficiently oxidizes Ce2O3 layers to CeO2. The

  14. Sintering of Spherical Particles of Equal and Different Size Arranged in a Body Centered Cubic Structure

    DEFF Research Database (Denmark)

    Redanz, Pia; McMeeking, R. M.

    2003-01-01

    to interact, or the next-nearest neighbours in the particle structure attain contact. Quantative measures of the density at the transition from open pore space between the particles to closed porosity as well as the density at which the next-nearest neighbours start to touch are derived. Furthermore...

  15. A polarimetric scattering database for non-spherical ice particles at microwave wavelengths

    Science.gov (United States)

    Lu, Yinghui; Jiang, Zhiyuan; Aydin, Kultegin; Verlinde, Johannes; Clothiaux, Eugene E.; Botta, Giovanni

    2016-10-01

    The atmospheric science community has entered a period in which electromagnetic scattering properties at microwave frequencies of realistically constructed ice particles are necessary for making progress on a number of fronts. One front includes retrieval of ice-particle properties and signatures from ground-based, airborne, and satellite-based radar and radiometer observations. Another front is evaluation of model microphysics by application of forward operators to their outputs and comparison to observations during case study periods. Yet a third front is data assimilation, where again forward operators are applied to databases of ice-particle scattering properties and the results compared to observations, with their differences leading to corrections of the model state. Over the past decade investigators have developed databases of ice-particle scattering properties at microwave frequencies and made them openly available. Motivated by and complementing these earlier efforts, a database containing polarimetric single-scattering properties of various types of ice particles at millimeter to centimeter wavelengths is presented. While the database presented here contains only single-scattering properties of ice particles in a fixed orientation, ice-particle scattering properties are computed for many different directions of the radiation incident on them. These results are useful for understanding the dependence of ice-particle scattering properties on ice-particle orientation with respect to the incident radiation. For ice particles that are small compared to the wavelength, the number of incident directions of the radiation is sufficient to compute reasonable estimates of their (randomly) orientation-averaged scattering properties. This database is complementary to earlier ones in that it contains complete (polarimetric) scattering property information for each ice particle - 44 plates, 30 columns, 405 branched planar crystals, 660 aggregates, and 640 conical

  16. Influence of Optimization of Process Parameters on Threshold Voltage for Development of HfO2/TiSi2 18 nm PMOS

    Directory of Open Access Journals (Sweden)

    Atan N.

    2016-01-01

    Full Text Available Manufacturing a 18-nm transistor requires a variety of parameters, materials, temperatures, and methods. In this research, HfO2 was used as the gate dielectric ad TiO2 was used as the gate material. The transistor HfO2/TiSi2 18-nm PMOS was invented using SILVACO TCAD. Ion implantation was adopted in the fabrication process for the method’s practicality and ability to be used to suppress short channel effects. The study involved ion implantation methods: compensation implantation, halo implantation energy, halo tilt, and source–drain implantation. Taguchi method is the best optimization process for a threshold voltage of HfO2/TiSi2 18-nm PMOS. In this case, the method adopted was Taguchi orthogonal array L9. The process parameters (ion implantations and noise factors were evaluated by examining the Taguchi’s signal-to-noise ratio (SNR and nominal-the-best for the threshold voltage (VTH. After optimization, the result showed that the VTH value of the 18-nm PMOS device was -0.291339.

  17. Propagation of a Strong Shock Over a Random Bed of Spherical Particles

    Energy Technology Data Exchange (ETDEWEB)

    Mehta, Y. [Univ. of Florida, Gainesville, FL (United States); Neal, C. [Univ. of Florida, Gainesville, FL (United States); Salari, K. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Jackson, T. L. [Univ. of Florida, Gainesville, FL (United States); Balachandar, S. [Univ. of Florida, Gainesville, FL (United States); Thakur, S. [Univ. of Florida, Gainesville, FL (United States)

    2017-04-11

    Propagation of a strong shock through a bed of particles results in complex wave dynamics such as a reflected shock, a transmitted shock, and highly unsteady flow inside the particle bed. In this paper we present three-dimensional numerical simulations of shock propagation in air over a random bed of particles. We assume the flow is inviscid and governed by the Euler equations of gas dynamics. Simulations are carried out by varying the volume fraction of the particle bed at a fixed shock Mach number. We compute the unsteady inviscid streamwise and transverse drag coefficients as a function of time for each particle in the random bed as a function of volume fraction. We show that (i) there are significant variations in the peak drag for the particles in the bed, (ii) the mean peak drag as a function of streamwise distance through the bed decreases with a slope that increases as the volume fraction increases, and (iii) the deviation from the mean peak drag does not correlate with local volume fraction. We also present the local Mach number and pressure contours for the different volume fractions to explain the various observed complex physical mechanisms occurring during the shock-particle interactions. Since the shock interaction with the random bed of particles leads to transmitted and reflected waves, we compute the average flow properties to characterize the strength of the transmitted and reflected shock waves and quantify the energy dissipation inside the particle bed. Finally, to better understand the complex wave dynamics in a random bed, we consider a simpler approximation of a planar shock propagating in a duct with a sudden area change. We obtain Riemann solutions to this problem, which are used to compare with fully resolved numerical simulations.

  18. Interaction forces between a deformable air bubble and a spherical particle of tuneable hydrophobicity and surface charge in aqueous solutions.

    Science.gov (United States)

    Englert, A H; Ren, S; Masliyah, J H; Xu, Z

    2012-08-01

    Interaction forces between an air bubble and a spherical particle of moderate and tuneable surface charge density and hydrophobicity in aqueous solutions were measured using atomic force microscopy. Bitumen coated silica spheres were used as model particles of tuneable charge density and hydrophobicity due to pH-dependent ionisation of carboxylic acids at bitumen-water interfaces. The measured force profiles showed a long-range repulsion prior to jump into contact, indicating the rupture of intervening liquid film between the bitumen and bubble surfaces. The long-range repulsive force increased with increasing pH. The measured force profiles were analysed by adopting the model originally developed by White and co-workers to account for deformation and change in shape of bubbles before rupture of the intervening liquid film. Satisfactory agreement between the theory and measured force profiles was obtained, showing the suitability of the model to describe the measured interaction forces. The model was then used to study the physical parameters on the particle-bubble interaction forces prior to three phase contact line (TPCL) formation. The hydrophobic decay length, surface potential and size of bubble and probe particles, and ionic strength of the medium (KCl concentration) were found to have a strong influence on the predicted force profiles. Copyright © 2012 Elsevier Inc. All rights reserved.

  19. DMC (Distinct Motion Code): A rigid body motion code for determining the interaction of multiple spherical particles

    Science.gov (United States)

    Taylor, L. M.; Preece, D. S.

    1989-07-01

    The computer program Distinct Motion Code (DMC) determines the two-dimensional planar rigid body motion of an arbitrary number of spherical shaped particles. The code uses an explicit central difference time integration algorithm to calculate the motion of the particles. Contact constraints between the particles are enforced using the penalty method. Coulomb friction and viscous damping are included in the collisions. The explicit time integration is conditionally stable with a time increment size which is dependent on the mass of the smallest particle in the mesh and the penalty stiffness used for the contact forces. The code chooses the spring stiffness based on the Young's modulus and Poisson's ratio of the material. The ability to tie spheres in pairs with a constraint condition is included in the code. The code has been written in an extremely efficient manner with particular emphasis placed on vector processing. While this does not impose any restrictions on non-vector processing computers, it does provide extremely fast results on vector processing computers. A bucket sorting or boxing algorithm is used to reduce the number of comparisons which must be made between spheres to determine the contact pairs. The sorting algorithm is completely algebraic and contains no logical branching.

  20. Compact and multi-view solid state neutral particle analyzer arrays on National Spherical Torus Experiment-Upgrade

    Energy Technology Data Exchange (ETDEWEB)

    Liu, D., E-mail: deyongl@uci.edu; Heidbrink, W. W.; Hao, G. Z.; Zhu, Y. B. [Departments of Physics and Astronomy, University of California, Irvine, California 92697 (United States); Tritz, K. [Departments of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Fredrickson, E. D. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)

    2016-11-15

    A compact and multi-view solid state neutral particle analyzer (SSNPA) diagnostic based on silicon photodiode arrays has been successfully tested on the National Spherical Torus Experiment-Upgrade. The SSNPA diagnostic provides spatially, temporally, and pitch-angle resolved measurements of fast-ion distribution by detecting fast neutral flux resulting from the charge exchange (CX) reactions. The system consists of three 16-channel subsystems: t-SSNPA viewing the plasma mid-radius and neutral beam (NB) line #2 tangentially, r-SSNPA viewing the plasma core and NB line #1 radially, and p-SSNPA with no intersection with any NB lines. Due to the setup geometry, the active CX signals of t-SSNPA and r-SSNPA are mainly sensitive to passing and trapped particles, respectively. In addition, both t-SSNPA and r-SSNPA utilize three vertically stacked arrays with different filter thicknesses to obtain coarse energy information. The experimental data show that all channels are operational. The signal to noise ratio is typically larger than 10, and the main noise is x-ray induced signal. The active and passive CX signals are clearly observed on t-SSNPA and r-SSNPA during NB modulation. The SSNPA data also indicate significant losses of passing particles during sawteeth, while trapped particles are weakly affected. Fluctuations up to 120 kHz have been observed on SSNPA, and they are strongly correlated with magnetohydrodynamics instabilities.

  1. Size measurement uncertainties of near-monodisperse, near-spherical nanoparticles using transmission electron microscopy and particle-tracking analysis

    Science.gov (United States)

    De Temmerman, Pieter-Jan; Verleysen, Eveline; Lammertyn, Jeroen; Mast, Jan

    2014-10-01

    Particle-tracking analysis (PTA) in combination with systematic imaging, automatic image analysis, and automatic data processing is validated for size measurements. Transmission electron microscopy (TEM) in combination with a systematic selection procedure for unbiased random image collection, semiautomatic image analysis, and data processing is validated for size, shape, and surface topology measurements. PTA is investigated as an alternative for TEM for the determination of the particle size in the framework of the EC definition of nanomaterial. The intra-laboratory validation study assessing the precision and accuracy of the TEM and PTA methods consists of series of measurements on three gold reference materials with mean area-equivalent circular diameters of 8.9 nm (RM-8011), 27.6 nm (RM-8012), and 56.0 nm (RM-8013), and two polystyrene materials with modal hydrodynamic diameters of 102 nm (P1) and 202 nm (H1). By obtaining a high level of automation, PTA proves to give precise and non-biased results for the modal hydrodynamic diameter in size range between 30 and 200 nm, and TEM proves to give precise and non-biased results for the mean area-equivalent circular diameter in the size range between 8 and 200 nm of the investigated near-monomodal near-spherical materials. The expanded uncertainties of PTA are about 9 % and are determined mainly by the repeatability uncertainty. This uncertainty is two times higher than the expanded uncertainty of 4 % obtained by TEM for analyses on identical materials. For the investigated near-monomodal and near-spherical materials, PTA can be used as an alternative to TEM for measuring the particle size, with exception of 8.9 nm gold, because this material has a size below the detection limit of PTA.

  2. Oxide-based inorganic/organic and nanoporous spherical particles: synthesis and functional properties

    Directory of Open Access Journals (Sweden)

    Kota Shiba, Motohiro Tagaya, Richard D Tilley and Nobutaka Hanagata

    2013-01-01

    Full Text Available This paper reviews the recent progress in the preparation of oxide-based and heteroatom-doped particles. Surfactant-templated oxide particles, e.g. silica and titania, are possible candidates for various potential applications such as adsorbents, photocatalysts, and optoelectronic and biological materials. We highlight nanoporous oxides of one element, such as silicon or titanium, and those containing multiple elements, which exhibit properties that are not achieved with individual components. Although the multicomponent nanoporous oxides possess a number of attractive functions, the origin of their properties is hard to determine due to compositional/structural complexity. Particles with a well-defined size and shape are keys for a quantitative and detailed discussion on the unique complex properties of the particles. From this viewpoint, we review the synthesis techniques of the oxide particles, which are functionalized with organic molecules or doped with heteroatoms, the physicochemical properties of the particles and the possibilities for their photofunctional applications as complex systems.

  3. Hyperfine anomalies in Fr: boundaries of the spherical single particle model

    CERN Document Server

    Zhang, J; Aubin, S; Behr, J A; Gomez, E; Gwinner, G; Orozco, L A; Pearson, M R; Sprouse, G D

    2015-01-01

    We have measured the hyperfine splitting of the $7P_{1/2}$ state at the 100 ppm level in Fr isotopes ($^{206g,206m, 207, 209, 213, 221}$Fr) near the closed neutron shell ($N$ = 126 in $^{213}$Fr). The measurements in five isotopes and a nuclear isomeric state of francium, combined with previous determinations of the $7S_{1/2}$ splittings, reveal the spatial distribution of the nuclear magnetization, i.e. the Bohr-Weisskopf effect. We compare our results with a simple shell model consisting of unpaired single valence nucleons orbiting a spherical nucleus, and find good agreement over a range of neutron-deficient isotopes ($^{207-213}$Fr). Also, we find near-constant proton anomalies for several even-$ N$ isotopes. This identifies a set of Fr isotopes whose nuclear structure can be understood well enough for the extraction of weak interaction parameters from parity non-conservation studies.

  4. Hyperfine Anomalies in Fr: Boundaries of the Spherical Single Particle Model

    Science.gov (United States)

    Zhang, J.; Tandecki, M.; Collister, R.; Aubin, S.; Behr, J. A.; Gomez, E.; Gwinner, G.; Orozco, L. A.; Pearson, M. R.; Sprouse, G. D.; FrPNC Collaboration

    2015-07-01

    We have measured the hyperfine splitting of the 7 P1 /2 state at the 100 ppm level in Fr isotopes (206g,206m,207,209,213,221Fr) near the closed neutron shell (N =126 in 213Fr). The measurements in five isotopes and a nuclear isomeric state of francium, combined with previous determinations of the 7 S1 /2 splittings, reveal the spatial distribution of the nuclear magnetization, i.e., the Bohr-Weisskopf effect. We compare our results with a simple shell model consisting of unpaired single valence nucleons orbiting a spherical nucleus, and find good agreement over a range of neutron-deficient isotopes (207-213Fr). Also, we find near-constant proton anomalies for several even-N isotopes. This identifies a set of Fr isotopes whose nuclear structure can be understood well enough for the extraction of weak interaction parameters from parity nonconservation studies.

  5. Acoustic radiation force due to arbitrary incident fields on spherical particles in soft tissue

    Energy Technology Data Exchange (ETDEWEB)

    Treweek, Benjamin C., E-mail: btreweek@utexas.edu; Ilinskii, Yurii A.; Zabolotskaya, Evgenia A.; Hamilton, Mark F. [Applied Research Laboratories, The University of Texas at Austin, P.O. Box 8029, Austin, TX 78713-8029 (United States)

    2015-10-28

    Acoustic radiation force is of interest in a wide variety of biomedical applications ranging from tissue characterization (e.g. elastography) to tissue treatment (e.g. high intensity focused ultrasound, kidney stone fragment removal). As tissue mechanical properties are reliable indicators of tissue health, the former is the focus of the present contribution. This is accomplished through an investigation of the acoustic radiation force on a spherical scatterer embedded in tissue. Properties of both the scatterer and the surrounding tissue are important in determining the magnitude and the direction of the force. As these properties vary, the force computation shows changes in magnitude and direction, which may enable more accurate noninvasive determination of tissue properties.

  6. Rebound mechanics of micrometre-scale, spherical particles in high-velocity impacts

    Science.gov (United States)

    Yildirim, Baran; Yang, Hankang; Gouldstone, Andrew; Müftü, Sinan

    2017-08-01

    The impact mechanics of micrometre-scale metal particles with flat metal surfaces is investigated for high-velocity impacts ranging from 50 m s-1 to more than 1 km s-1, where impact causes predominantly plastic deformation. A material model that includes high strain rate and temperature effects on the yield stress, heat generation due to plasticity, material damage due to excessive plastic strain and heat transfer is used in the numerical analysis. The coefficient of restitution e is predicted by the classical work using elastic-plastic deformation analysis with quasi-static impact mechanics to be proportional to Vi-1 / 4 and Vi-1 / 2 for the low and moderate impact velocities that span the ranges of 0-10 and 10-100 m s-1, respectively. In the elastic-plastic and fully plastic deformation regimes the particle rebound is attributed to the elastic spring-back that initiates at the particle-substrate interface. At higher impact velocities (0.1-1 km s-1) e is shown to be proportional to approximately Vi-1. In this deeply plastic deformation regime various deformation modes that depend on plastic flow of the material including the time lag between the rebound instances of the top and bottom points of particle and the lateral spreading of the particle are identified. In this deformation regime, the elastic spring-back initiates subsurface, in the substrate.

  7. SPH modeling and simulation of spherical particles interacting in a viscoelastic matrix

    Science.gov (United States)

    Vázquez-Quesada, A.; Ellero, M.

    2017-12-01

    In this work, we extend the three-dimensional Smoothed Particle Hydrodynamics (SPH) non-colloidal particulate model previously developed for Newtonian suspending media in Vázquez-Quesada and Ellero ["Rheology and microstructure of non-colloidal suspensions under shear studied with smoothed particle hydrodynamics," J. Non-Newtonian Fluid Mech. 233, 37-47 (2016)] to viscoelastic matrices. For the solvent medium, the coarse-grained SPH viscoelastic formulation proposed in Vázquez-Quesada, Ellero, and Español ["Smoothed particle hydrodynamic model for viscoelastic fluids with thermal fluctuations," Phys. Rev. E 79, 056707 (2009)] is adopted. The property of this particular set of equations is that they are entirely derived within the general equation for non-equilibrium reversible-irreversible coupling formalism and therefore enjoy automatically thermodynamic consistency. The viscoelastic model is derived through a physical specification of a conformation-tensor-dependent entropy function for the fluid particles. In the simple case of suspended Hookean dumbbells, this delivers a specific SPH discretization of the Oldroyd-B constitutive equation. We validate the suspended particle model by studying the dynamics of single and mutually interacting "noncolloidal" rigid spheres under shear flow and in the presence of confinement. Numerical results agree well with available numerical and experimental data. It is straightforward to extend the particulate model to Brownian conditions and to more complex viscoelastic solvents.

  8. Energetically favoured defects in dense packings of particles on spherical surfaces

    Science.gov (United States)

    Paquay, Stefan; Kusumaatmaja, Halim; Wales, David J.; Zandi, Roya; van der Schoot, Paul

    The dense packing of interacting particles on spheres has proved to be a useful model for virus capsids and colloidosomes. Indeed, icosahedral symmetry observed in virus capsids corresponds to potential energy minima that occur for magic numbers of, e.g., 12, 32 and 72 identical Lennard-Jones particles, for which the packing has exactly the minimum number of twelve five-fold defects. It is unclear, however, how stable these structures are against thermal agitation. We investigate this property by means of basin-hopping global optimisation and Langevin dynamics for particle numbers between ten and one hundred. An important measure is the number and type of point defects, that is, particles that do not have six nearest neighbours. We find that small icosahedral structures are the most robust against thermal fluctuations, exhibiting fewer excess defects and rearrangements for a wide temperature range. Furthermore, we provide evidence that excess defects appearing at low non-zero temperatures lower the potential energy at the expense of entropy. At higher temperatures defects are, as expected, thermally excited and thus entropically stabilised. If we replace the Lennard-Jones potential by a very short-ranged (Morse) potential, which is arguably more appropriate for colloids and virus capsid proteins, we find that the same particle numbers give a minimum in the potential energy, although for larger particle numbers these minima correspond to different packings. Furthermore, defects are more difficult to excite thermally for the short-ranged potential, suggesting that the short-ranged interaction further stabilises equilibrium structures.

  9. Influence of erythrocyte aggregation on radial migration of platelet-sized spherical particles in shear flow.

    Science.gov (United States)

    Guilbert, Cyrille; Chayer, Boris; Allard, Louise; Yu, François T H; Cloutier, Guy

    2017-08-16

    Blood platelets when activated are involved in the mechanisms of hemostasis and thrombosis, and their migration toward injured vascular endothelium necessitates interaction with red blood cells (RBCs). Rheology co-factors such as a high hematocrit and a high shear rate are known to promote platelet mass transport toward the vessel wall. Hemodynamic conditions promoting RBC aggregation may also favor platelet migration, particularly in the venous system at low shear rates. The aim of this study was to confirm experimentally the impact of RBC aggregation on platelet-sized micro particle migration in a Couette flow apparatus. Biotin coated micro particles were mixed with saline or blood with different aggregation tendencies, at two shear rates of 2 and 10s(-1) and three hematocrits ranging from 20 to 60%. Streptavidin membranes were respectively positioned on the Couette static and rotating cylinders upon which the number of adhered fluorescent particles was quantified. The platelet-sized particle adhesion on both walls was progressively enhanced by increasing the hematocrit (p<0.001), reducing the shear rate (p<0.001), and rising the aggregation of RBCs (p<0.001). Particle count was minimum on the stationary cylinder when suspended in saline at 2s(-1) (57±33), and maximum on the rotating cylinder at 60% hematocrit, 2s(-1) and the maximum dextran-induced RBC aggregation (2840±152). This fundamental study is confirming recent hypotheses on the role of RBC aggregation on venous thrombosis, and may guide molecular imaging protocols requiring injecting active labeled micro particles in the venous flow system to probe human diseases. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. New method for mass transfer across the surface of non-spherical particles in turbulence

    Science.gov (United States)

    Oehmke, T.; Variano, E. A.

    2016-12-01

    We present a method for making model particles that allow for the interfacial mass transfer rate to be measured. This is similar to traditional use of gypsum plaster used to measure erosion rates on the timescale of weeks to years. Our new method is useful for measuring erosion rates on the timescale of minutes. We use this to measure the manner in which particle shape affects its rate of dissolution in turbulent flow. The related questions are relevant to mass transfer in turbulence, e.g. in cases of marine biology and pollution by microplastics.

  11. A model derived from hydrodynamic simulations for extracting the size of spherical particles from the quartz crystal microbalance.

    Science.gov (United States)

    Gillissen, Jurriaan J J; Tabaei, Seyed R; Jackman, Joshua A; Cho, Nam-Joon

    2017-09-08

    One challenging aspect of quartz crystal microbalance (QCM) measurements is the characterization of adsorbed particles as the change in resonance frequency (Δf) is proportional not only to the inertia of the adsorbed layer but also to that of the hydrodynamically coupled fluid. Herein, by solving numerically the Navier-Stokes equations, we scrutinize Δf for sparsely deposited, rigid spherical particles that are firmly attached to an oscillating surface. The analysis is shown to be applicable to adsorbed, small unilamellar vesicles (SUVs) of controlled size under experimental conditions in which adhesion-induced vesicle deformation is negligible. The model supports a hydrodynamic explanation for the overtone dependence of Δf, and was fitted to experimental data concerning three monodisperse populations of SUVs with different average sizes ranging between 56 and 114 nm diameter. Using this procedure, we determined the average size of adsorbed vesicles to be within 16% of the size that was measured by dynamic light scattering experiments in bulk solution. In conclusion, this model offers a means to extract the particle size from QCM-D measurement data, with applications to biological and synthetic nanoparticles.

  12. Capillary forces between spherical particles floating at a liquid-liquid interface

    NARCIS (Netherlands)

    Vassileva, Nikolina D.; drs. Vassileva, N.D.; van den Ende, Henricus T.M.; Mugele, Friedrich Gunther; Mellema, J.

    2005-01-01

    We study the capillary forces acting on sub-millimeter particles (0.02-0.6 mm) trapped at a liquid-liquid interface due to gravity-induced interface deformations. An analytical procedure is developed to solve the linearized capillary (Young-Laplace) equation and calculate the forces for an arbitrary

  13. On the reorientation of non-spherical prey particles in a feeding current

    DEFF Research Database (Denmark)

    Visser, Andre; Jonsson, P.R.

    2000-01-01

    of its shape, size and the characteristics of the fluid flow For a radial flow field, elongated prey tend to align with their long axis parallel to streamlines. This theory is well supported by our results from a laboratory study of cylindrical particles in a siphon flow. The model is extended to a more...

  14. Energetically favoured defects in dense packings of particles on spherical surfaces

    NARCIS (Netherlands)

    Paquay, Stefan; Kusumaatmaja, Halim; Wales, David J.; Zandi, Roya; Schoot, Paul van der|info:eu-repo/dai/nl/102140618

    2016-01-01

    The dense packing of interacting particles on spheres has proved to be a useful model for virus capsids and colloidosomes. Indeed, icosahedral symmetry observed in virus capsids corresponds to potential energy minima that occur for magic numbers of, e.g., 12, 32 and 72 identical Lennard-Jones

  15. Plasma diagnostics in spherical tokamaks with silicon charged-particle detectors

    Energy Technology Data Exchange (ETDEWEB)

    Netepenko, A., E-mail: anete001@fiu.edu; Boeglin, W. U. [Department of Physics, Florida International University, Miami, Florida 33199 (United States); Darrow, D. S.; Ellis, R.; Sibilia, M. J. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)

    2016-11-15

    Detection of charged fusion products, such as protons and tritons resulting from D(d, p) t reactions, can be used to determine the position and time dependent fusion reaction rate profile in spherical tokamak plasmas with neutral beam heating. We have developed a prototype instrument consisting of 6 ion-implanted-silicon surface barrier detectors combined with collimators in such a way that each detector can accept 3 MeV protons and 1 MeV tritons and thus provides a curved view across the plasma cross section. The combination of the results from all six detectors will provide information on the spatial distribution of the fusion reaction rate. The expected time resolution of about 1 ms makes it possible to study changes in the reaction rate due to slow variations in the neutral beam density profile, as well as rapid changes resulting from MHD instabilities. Details of the new instrument, its data acquisition system, simulation results, and electrical noise testing results are discussed in this paper. First experimental data are expected to be taken during the current experimental campaign at NSTX-U.

  16. A model experiment to study swallowing of spherical and elongated particles

    Science.gov (United States)

    Marconati, Marco; Raut, Sharvari; Charkhi, Farshad; Burbidge, Adam; Engmann, Jan; Ramaioli, Marco

    2017-06-01

    Swallowing disorders are not uncommon among elderly and people affected by neurological diseases. For these patients the ingestion of solid grains, such as pharmaceutical oral solid formulations, could result in choking. This generally results in a low compliance in taking solid medications. The effect of the solid medication size on the real or perceived ease of swallowing is still to be understood from the mechanistic viewpoint. The interplay of the inclusion shape and the rheology of the liquid being swallowed together with the medication is also not fully understood. In this study, a model experiment was developed to study the oropharyngeal phase of swallowing, replicating the dynamics of the bolus flow induced by the tongue (by means of a roller driven by an applied force). Experiments were performed using a wide set of solid inclusions, dispersed in a thick Newtonian liquid. Predictions for a simple theory are compared with experiments. Results show that an increase in the grain size results in a slower dynamics of the swallowing. Furthermore, the experiments demonstrated the paramount role of shape, as flatter and more streamlined inclusions flow faster than spherical. This approach can support the design of new oral solid formulations that can be ingested more easily and effectively also by people with mild swallowing disorders.

  17. A model experiment to study swallowing of spherical and elongated particles

    Directory of Open Access Journals (Sweden)

    Marconati Marco

    2017-01-01

    Full Text Available Swallowing disorders are not uncommon among elderly and people affected by neurological diseases. For these patients the ingestion of solid grains, such as pharmaceutical oral solid formulations, could result in choking. This generally results in a low compliance in taking solid medications. The effect of the solid medication size on the real or perceived ease of swallowing is still to be understood from the mechanistic viewpoint. The interplay of the inclusion shape and the rheology of the liquid being swallowed together with the medication is also not fully understood. In this study, a model experiment was developed to study the oropharyngeal phase of swallowing, replicating the dynamics of the bolus flow induced by the tongue (by means of a roller driven by an applied force. Experiments were performed using a wide set of solid inclusions, dispersed in a thick Newtonian liquid. Predictions for a simple theory are compared with experiments. Results show that an increase in the grain size results in a slower dynamics of the swallowing. Furthermore, the experiments demonstrated the paramount role of shape, as flatter and more streamlined inclusions flow faster than spherical. This approach can support the design of new oral solid formulations that can be ingested more easily and effectively also by people with mild swallowing disorders.

  18. Settling speed of non-spherical particles in drilling fluid; Velocidade de sedimentacao de particulas nao esfericas em fluidos de perfuracao

    Energy Technology Data Exchange (ETDEWEB)

    Santana, Cesar C.; Laruccia, Moacyr B.; Maidla, Eric E. [Universidade Estadual de Campinas, SP (Brazil)

    1989-07-01

    In this paper, we develop a correlation for the calculation of the drift coefficient of non-spherical particles settling in non-Newtonian fluids, regardless of time. The use of Dimensional Analysis and of a great amount of experimental data covering laminar, intermediary and turbulent regimes brought about a generalized correlation to determine particle settling speed in a sphericity range of 0.5 to 1.0. In contrast to results published by other authors, the correlation developed in this paper does not depend on a particular rheological model of the fluid. (author) 13 refs., 17 figs., 3 tabs.

  19. Development of new polysilsesquioxane spherical particles as stabilized active ingredients for sunscreens

    Science.gov (United States)

    Tolbert, Stephanie Helene

    Healthy skin is a sign of positive self-worth, attractiveness and vitality. Compromises to this are frequently caused by extended periods of recreation in the sun and in turn exposure to the harmful effects of UV radiation. To maintain strength and integrity, protection of the skin is paramount. This can be achieved by implementing skin-care products which contain sunscreen active ingredients that provide UV protection. Unfortunately, photo-degradation, toxicity, and photo-allergies limit the effectiveness of present day sunscreen ingredients. Currently, this is moderated by physically embedding within inert silica particles, but leaching of the active ingredient can occur, thereby negating protective efforts. Alternatively, this research details the preparation and investigation of bridged silsesquioxane analogues of commercial ingredients which can be chemically grafted to the silica matrix. Studies with bridged salicylate particles detail facile preparation, minimized leaching, and enhanced UV stability over physically encapsulated and pendant salicylate counterparts. In terms of UVB protective ability, the highest maintenance of sun protection factor (SPF) after extended UV exposure was achieved with bridged incorporation, and has been attributed to corollary UV stability. Additionally, bridged salicylate particles can be classified as broad-spectrum, and rate from moderate to good in terms of UVA protective ability. Particles incorporated with a bridged curcuminoid silsesquioxane were also prepared and displayed comparable results. As such, an attractive method for sunscreen isolation and stabilization has been developed to eliminate the problems associated with current sunscreens, all while maintaining the established UV absorbance profiles of the parent compound. To appreciate the technology utilized in this research, a thorough understanding of sol-gel science as it pertains to hybrid organic/silica particles, including methods of organic fragment

  20. Light Scattering by Marine Particles: Modeling with Non-Spherical Shapes

    Science.gov (United States)

    2011-04-15

    atoms (molecules). At a great distance f from the particle the field due to the dipole moment induced in dVt is </£<*> = —jcxlicxdp&j- rjc )], (3...0) exp[/(v0 • £>, - cot + ^co/c)] dV, . Then noting that K - co I c, we have ^col c = Kri = Kr-K*bf dp^t- rJc ^pjaUD,)^ exp[/(/r0 -K)• £.]exp[/(*r

  1. Filter-based Aerosol Measurement Experiments using Spherical Aerosol Particles under High Temperature and High Pressure

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jong Chan; Jung, Woo Young; Lee, Hyun Chul; Lee, Doo Young [FNC TECH., Yongin (Korea, Republic of)

    2016-05-15

    Optical Particle Counter (OPC) is used to provide real-time measurement of aerosol concentration and size distribution. Glass fiber membrane filter also be used to measure average mass concentration. Three tests (MTA-1, 2 and 3) have been conducted to study thermal-hydraulic effect, a filtering tendency at given SiO{sub 2} particles. Based on the experimental results, the experiment will be carried out further with a main carrier gas of steam and different aerosol size. The test results will provide representative behavior of the aerosols under various conditions. The aim of the tests, MTA 1, 2 and 3, are to be able to 1) establish the test manuals for aerosol generation, mixing, sampling and measurement system, which defines aerosol preparation, calibration, operating and evaluation method under high pressure and high temperature 2) develop commercial aerosol test modules applicable to the thermal power plant, environmental industry, automobile exhaust gas, chemical plant, HVAC system including nuclear power plant. Based on the test results, sampled aerosol particles in the filter indicate that important parameters affecting aerosol behavior aerosols are 1) system temperature to keep above a evaporation temperature of ethanol and 2) aerosol losses due to the settling by ethanol liquid droplet.

  2. Anomalous forward scattering of gain-assisted dielectric shell-coated metallic core spherical particles

    Science.gov (United States)

    Shen, Fei; An, Ning; Tao, Yifei; Zhou, Hongping; Jiang, Zhaoneng; Guo, Zhongyi

    2017-08-01

    We have investigated the scattering properties of an individual core-shell nanoparticle using the Mie theory, which can be tuned to support both electric and magnetic modes simultaneously. In general, the suppression of forward scattering can be realized by the second Kerker condition. Here, a novel mechanism has to be adopted to explain zero-forward scattering, which originates from the complex interactions between dipolar and quadrupolar modes. However, for lossy and lossless core-shell spherical nanoparticles, zero-forward scattering can never be achieved because the real parts of Mie expansion coefficients are always positive. By adding proper gain in dielectric shell, zero-forward scattering can be found at certain incident wavelengths, which means that all electric and magnetic responses in Mie scattering can be counteracted totally in the forward direction. In addition, if the absolute values of dipolar and quadrupolar terms are in the same order of magnitude, the local scattering minimum and maximum can be produced away from the forward and backward directions due to the interacting effect between the dipolar and quadrupolar terms. Furthermore, by adding suitable gain in shell, super-forward scattering can also be realized at certain incident wavelengths. We also demonstrated that anomalously weak scattering or superscattering could be obtained for the core-shell nanoparticles with suitable gain in shell. In particular, for such a choice of suitable gain in shell, we can obtain zero-forward scattering and anomalously weak scattering at the same wavelength as well as super-forward scattering at another wavelength. These features may provide new opportunities for cloaking, plasmonic lasers, optical antennas, and so on.

  3. Effect of Particle Non-Sphericity on Satellite Monitoring of Drifting Volcanic Ash Clouds

    Science.gov (United States)

    Krotkov, Nicholay A.; Flittner, D. E.; Krueger, A. J.; Kostinski, A.; Riley, C.; Rose, W.

    1998-01-01

    Volcanic eruptions loft gases and ash particles into the atmosphere and produce effects that are both short term (aircraft hazards, interference with satellite measurements) and long term (atmospheric chemistry, climate). Large (greater than 0.5mm) ash particles fall out in minutes [Rose et al, 1995], but fine ash particles can remain in the atmosphere for many days. This fine volcanic ash is a hazard to modem jet aircraft because the operating temperatures of jet engines are above the solidus temperature of volcanic ash, and because ash causes abrasion of windows and airframe, and disruption of avionics. At large distances(10(exp 2)-10(exp 4) km or more) from their source, drifting ash clouds are increasingly difficult to distinguish from meteorological clouds, both visually and on radar [Rose et al., 1995]. Satellites above the atmosphere are unique platforms for viewing volcanic clouds on a global basis and measuring their constituents and total mass. Until recently, only polar AVHRR and geostationary GOES instruments could be used to determine characteristics of drifting volcanic ash clouds using the 10-12 micron window [Prata 1989; Wen and Rose 1994; Rose and Schneider 1996]. The NASA Total Ozone Mapping Spectrometer (TOMS) instruments aboard the Nimbus-7, Meteor3, ADEOS, and Earth Probe satellites have produced a unique data set of global SO2 volcanic emissions since 1978 (Krueger et al., 1995). Besides SO2, a new technique has been developed which uses the measured spectral contrast of the backscattered radiances in the 330-380nm spectral region (where gaseous absorption is negligible) in conjunction with radiative transfer models to retrieve properties of volcanic ash (Krotkov et al., 1997) and other types of absorbing aerosols (Torres et al., 1998).

  4. Spherical bioactive glass particles and their interaction with human mesenchymal stem cells in vitro.

    Science.gov (United States)

    Labbaf, Sheyda; Tsigkou, Olga; Müller, Karin H; Stevens, Molly M; Porter, Alexandra E; Jones, Julian R

    2011-02-01

    Sub-micron particles of bioactive glass (SMBGs) with composition 85 mol% SiO(2) and 15 mol% CaO were synthesised and characterised. Bioactivity was demonstrated by the formation of calcium apatite following 5 days immersion in simulated body fluid (SBF). The effect of a 24 h exposure of SMBGs (100 μg/ml, 150 μg/ml, 200 μg/ml) to human mesenchymal stem cells (hMSCs) on cell viability, metabolic activity and proliferation were determined using the LIVE/DEAD, MTT, total DNA and LDH assays after 1, 4 and 7 days of culture. None of the SMBG concentrations caused significant cytotoxicity at 1 and 4 days, but the doses of 150 and 200 μg/ml significantly decreased hMSC metabolic activity after 7 days of culture. Cell proliferation decreased as SMBG concentration increased; however none of the SMBGs tested had a significant effect on DNA quantity compared to the control. Confocal microscopy confirmed cellular uptake and localisation of the SMBGs in the hMSC cytoskeleton. Transmission electron microscopy revealed that the SMBGs localised inside the cell cytoplasm and cell endosomes. These findings are important for assessing the toxicity of sub-micron particles that may either be used as injectables for bone regeneration or generated by wear or degradation of bioactive glass scaffolds. Copyright © 2010 Elsevier Ltd. All rights reserved.

  5. Influence of Spherical Particle Size Distribution on Pressure Gradients in Mixed Bed

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jin Ho; Lee, Moon Eon; Kim, Eun Ho; Park, Hyun Sun [POSTECH, Pohang (Korea, Republic of)

    2016-05-15

    It is of key importance to ensure the long-term cooling of the relocated corium on the reactor containment floor by supplying coolant into the debris bed for stabilization and termination of the severe accident progression. Since the cooling mechanism is governed by pressure gradients which depend on the debris bed characteristics such as particle morphology, size distribution and bed porosity etc., it is necessary to investigate the two-phase flow pressure gradient mechanism in the debris bed under the conditions of hypothetical severe accident cases. The debris bed characteristics in such accident conditions can be found from previous molten fuel-coolant interactions (FCIs) studies. In the FCIs experiments, the quenched particulate debris bed is composed of irregular shape particles with size distribution from a few of micrometers to about 10 mm. For water/air two-phase experiment, The Tung and Dhir model using the length mean diameter can predict the counter-current flow limitation although it does not predict the measured pressure gradients well for the whole range of the superficial air velocity.

  6. Generating Irregular Models for 3D Spherical-Particle-Based Numerical Methods

    Directory of Open Access Journals (Sweden)

    Gang-Hai Huang

    2013-01-01

    Full Text Available The realistic representation of an irregular geological body is essential to the construction of a particle simulation model. A three-dimensional (3D sphere generator for an irregular model (SGIM, which is based on the platform of Microsoft Foundation Classes (MFC in VC++, is developed to accurately simulate the inherent discontinuities in geological bodies. OpenGL is employed to visualize the modeling in the SGIM. Three key functions, namely, the basic-model-setup function, the excavating function, and the cutting function, are implemented. An open-pit slope is simulated using the proposed model. The results demonstrate that an extremely irregular 3D model of a geological body can be generated using the SGIM and that various types of discontinuities can be inserted to cut the model. The data structure of the model that is generated by the SGIM is versatile and can be easily modified to match various numerical calculation tools. This can be helpful in the application of particle simulation methods to large-scale geoengineering projects.

  7. Fundamental measure theory for non-spherical hard particles: predicting liquid crystal properties from the particle shape.

    Science.gov (United States)

    Wittmann, René; Marechal, Matthieu; Mecke, Klaus

    2016-06-22

    Density functional theory (DFT) for hard bodies provides a theoretical description of the effect of particle shape on inhomogeneous fluids. We present improvements of the DFT framework fundamental measure theory (FMT) for hard bodies and validate these improvements for hard spherocylinders. To keep the paper self-contained, we first discuss the recent advances in FMT for hard bodies that lead to the introduction of fundamental mixed measure theory (FMMT) in our previous paper (2015 Europhys. Lett. 109 26003). Subsequently, we provide an efficient semi-empirical alternative to FMMT and show that the phase diagram for spherocylinders is described with similar accuracy in both versions of the theory. Finally, we present a semi-empirical modification of FMMT whose predictions for the phase diagram for spherocylinders are in excellent quantitative agreement with computer simulation results.

  8. Classical Particle in Presence of Magnetic Field, Hyperbolic Lobachevsky and Spherical Riemann Models

    Directory of Open Access Journals (Sweden)

    V.V. Kudryashov

    2010-01-01

    Full Text Available Motion of a classical particle in 3-dimensional Lobachevsky and Riemann spaces is studied in the presence of an external magnetic field which is analogous to a constant uniform magnetic field in Euclidean space. In both cases three integrals of motions are constructed and equations of motion are solved exactly in the special cylindrical coordinates on the base of the method of separation of variables. In Lobachevsky space there exist trajectories of two types, finite and infinite in radial variable, in Riemann space all motions are finite and periodical. The invariance of the uniform magnetic field in tensor description and gauge invariance of corresponding 4-potential description is demonstrated explicitly. The role of the symmetry is clarified in classification of all possible solutions, based on the geometric symmetry group, SO(3,1 and SO(4 respectively.

  9. Adsorption of cellulose derivatives on flat gold surfaces and on spherical gold particles.

    Science.gov (United States)

    Amirkhani, Masoud; Volden, Sondre; Zhu, Kaizheng; Glomm, Wilhelm R; Nyström, Bo

    2008-12-01

    The adsorption of hydroxyethylcellulose (HEC), ethyl(hydroxyethyl)cellulose (EHEC), and their hydrophobically modified counterparts HM-HEC and HM-EHEC has been studied on planar gold and citrate-covered gold surfaces by means of quartz crystal microbalance with dissipation monitoring (QCM-D), and on citrate-covered gold particles with the aid of dynamic light scattering (DLS). The QCM-D results indicate that larger amounts of polymer are adsorbed from aqueous solutions of HM-HEC and HM-EHEC on both substrates than from solutions of their unmodified analogues. The adsorption affinity for all the polymers, except EHEC, is higher on the citrate-covered surfaces than on the bare gold substrate. This indicates that more adsorption sites are activated in the presence of the citrate layer. The experimental adsorption data for all the polymers can be described fairly well by the Langmuir adsorption isotherm. However, at very low polymer concentrations significant deviations from the model are observed. The value of the hydrodynamic thickness of the adsorbed polymer layer (delta h), determined from DLS, rises with increasing polymer concentration for all the cellulose derivatives; a Langmuir type of isotherm can be used to roughly describe the adsorption behavior. Because of good solvent conditions for HEC the chains extend far out in the bulk at higher concentrations and the value of delta h is much higher than that of HM-HEC. The adsorption of EHEC and HM-EHEC onto gold particles discloses that the values of delta h are considerably higher for the hydrophobically modified cellulose derivative, and this finding is compatible with the trend in layer thickness estimated from the QCM-D measurements.

  10. Transverse sphericity of primary charged particles in minimum bias proton–proton collisions at √s= 0.9, 2.76 and 7 TeV

    NARCIS (Netherlands)

    Abelev, B.I.; Adam, J.; Bjelogrlic, S|info:eu-repo/dai/nl/355079615; Chojnacki, M.; Christakoglou, P.; de Rooij, R. S.; Grelli, A.|info:eu-repo/dai/nl/326052577; La Pointe, S.L.; Luparello, G.|info:eu-repo/dai/nl/355080400; Mischke, A.|info:eu-repo/dai/nl/325781435; Nooren, G.J.L.|info:eu-repo/dai/nl/07051349X; Peitzmann, T.|info:eu-repo/dai/nl/304833959; Reicher, M|info:eu-repo/dai/nl/32823219X; Snellings, R.J.M.|info:eu-repo/dai/nl/165585781; Thomas, D; van Leeuwen, M.|info:eu-repo/dai/nl/250599171; Veldhoen, M; Verweij, M.; Zhou, Y.; Zyzak, M.

    2012-01-01

    Measurements of the sphericity of primary charged particles in minimum bias proton–proton collisions at √ s = 0.9, 2.76 and 7 TeV with the ALICE detector at the LHC are presented. The observable is measured in the plane perpendicular to the beam direction using primary charged tracks with pT > 0.5

  11. Transverse sphericity of primary charged particles in minimum bias proton-proton collisions at $\\sqrt{s}$=0.9, 2.76 and 7 TeV

    CERN Document Server

    Abelev, Betty; Adamova, Dagmar; Adare, Andrew Marshall; Aggarwal, Madan; Aglieri Rinella, Gianluca; Agocs, Andras Gabor; Agostinelli, Andrea; Aguilar Salazar, Saul; Ahammed, Zubayer; Ahmad, Arshad; Ahmad, Nazeer; Ahn, Sul-Ah; Ahn, Sang Un; Akindinov, Alexander; Aleksandrov, Dmitry; Alessandro, Bruno; Alfaro Molina, Jose Ruben; Alici, Andrea; Alkin, Anton; Almaraz Avina, Erick Jonathan; Alme, Johan; Alt, Torsten; Altini, Valerio; Altinpinar, Sedat; Altsybeev, Igor; Andrei, Cristian; Andronic, Anton; Anguelov, Venelin; Anielski, Jonas; Anson, Christopher Daniel; Anticic, Tome; Antinori, Federico; Antonioli, Pietro; Aphecetche, Laurent Bernard; Appelshauser, Harald; Arbor, Nicolas; Arcelli, Silvia; Arend, Andreas; Armesto, Nestor; Arnaldi, Roberta; Aronsson, Tomas Robert; Arsene, Ionut Cristian; Arslandok, Mesut; Asryan, Andzhey; Augustinus, Andre; Averbeck, Ralf Peter; Awes, Terry; Aysto, Juha Heikki; Azmi, Mohd Danish; Bach, Matthias Jakob; Badala, Angela; Baek, Yong Wook; Bailhache, Raphaelle Marie; Bala, Renu; Baldini Ferroli, Rinaldo; Baldisseri, Alberto; Baldit, Alain; Baltasar Dos Santos Pedrosa, Fernando; Ban, Jaroslav; Baral, Rama Chandra; Barbera, Roberto; Barile, Francesco; Barnafoldi, Gergely Gabor; Barnby, Lee Stuart; Barret, Valerie; Bartke, Jerzy Gustaw; Basile, Maurizio; Bastid, Nicole; Basu, Sumit; Bathen, Bastian; Batigne, Guillaume; Batyunya, Boris; Baumann, Christoph Heinrich; Bearden, Ian Gardner; Beck, Hans; Behera, Nirbhay Kumar; Belikov, Iouri; Bellini, Francesca; Bellwied, Rene; Belmont-Moreno, Ernesto; Bencedi, Gyula; Beole, Stefania; Berceanu, Ionela; Bercuci, Alexandru; Berdnikov, Yaroslav; Berenyi, Daniel; Bergognon, Anais Annick Erica; Berzano, Dario; Betev, Latchezar; Bhasin, Anju; Bhati, Ashok Kumar; Bhom, Jihyun; Bianchi, Livio; Bianchi, Nicola; Bianchin, Chiara; Bielcik, Jaroslav; Bielcikova, Jana; Bilandzic, Ante; Bjelogrlic, Sandro; Blanco, F; Blanco, Francesco; Blau, Dmitry; Blume, Christoph; Boccioli, Marco; Bock, Nicolas; Boettger, Stefan; Bogdanov, Alexey; Boggild, Hans; Bogolyubsky, Mikhail; Boldizsar, Laszlo; Bombara, Marek; Book, Julian; Borel, Herve; Borissov, Alexander; Bose, Suvendu Nath; Bossu, Francesco; Botje, Michiel; Boyer, Bruno Alexandre; Braidot, Ermes; Braun-Munzinger, Peter; Bregant, Marco; Breitner, Timo Gunther; Browning, Tyler Allen; Broz, Michal; Brun, Rene; Bruna, Elena; Bruno, Giuseppe Eugenio; Budnikov, Dmitry; Buesching, Henner; Bufalino, Stefania; Bugaiev, Kyrylo; Busch, Oliver; Buthelezi, Edith Zinhle; Caballero Orduna, Diego; Caffarri, Davide; Cai, Xu; Caines, Helen Louise; Calvo Villar, Ernesto; Camerini, Paolo; Canoa Roman, Veronica; Cara Romeo, Giovanni; Carena, Francesco; Carena, Wisla; Carlin Filho, Nelson; Carminati, Federico; Carrillo Montoya, Camilo Andres; Casanova Diaz, Amaya Ofelia; Castillo Castellanos, Javier Ernesto; Castillo Hernandez, Juan Francisco; Casula, Ester Anna Rita; Catanescu, Vasile; Cavicchioli, Costanza; Ceballos Sanchez, Cesar; Cepila, Jan; Cerello, Piergiorgio; Chang, Beomsu; Chapeland, Sylvain; Charvet, Jean-Luc Fernand; Chattopadhyay, Subhasis; Chattopadhyay, Sukalyan; Chawla, Isha; Cherney, Michael Gerard; Cheshkov, Cvetan; Cheynis, Brigitte; Chibante Barroso, Vasco Miguel; Chinellato, David; Chochula, Peter; Chojnacki, Marek; Choudhury, Subikash; Christakoglou, Panagiotis; Christensen, Christian Holm; Christiansen, Peter; Chujo, Tatsuya; Chung, Suh-Urk; Cicalo, Corrado; Cifarelli, Luisa; Cindolo, Federico; Cleymans, Jean Willy Andre; Coccetti, Fabrizio; Colamaria, Fabio; Colella, Domenico; Conesa Balbastre, Gustavo; Conesa del Valle, Zaida; Constantin, Paul; Contin, Giacomo; Contreras, Jesus Guillermo; Cormier, Thomas Michael; Corrales Morales, Yasser; Cortese, Pietro; Cortes Maldonado, Ismael; Cosentino, Mauro Rogerio; Costa, Filippo; Cotallo, Manuel Enrique; Crescio, Elisabetta; Crochet, Philippe; Cruz Alaniz, Emilia; Cuautle, Eleazar; Cunqueiro, Leticia; Dainese, Andrea; Dalsgaard, Hans Hjersing; Danu, Andrea; Das, Debasish; Das, Indranil; Das, Kushal; Dash, Sadhana; Dash, Ajay Kumar; De, Sudipan; de Barros, Gabriel; De Caro, Annalisa; de Cataldo, Giacinto; de Cuveland, Jan; De Falco, Alessandro; De Gruttola, Daniele; Delagrange, Hugues; Deloff, Andrzej; Demanov, Vyacheslav; De Marco, Nora; Denes, Ervin; De Pasquale, Salvatore; Deppman, Airton; D'Erasmo, Ginevra; de Rooij, Raoul Stefan; Diaz Corchero, Miguel Angel; Di Bari, Domenico; Dietel, Thomas; Di Giglio, Carmelo; Di Liberto, Sergio; Di Mauro, Antonio; Di Nezza, Pasquale; Divia, Roberto; Djuvsland, Oeystein; Dobrin, Alexandru Florin; Dobrowolski, Tadeusz Antoni; Dominguez, Isabel; Donigus, Benjamin; Dordic, Olja; Driga, Olga; Dubey, Anand Kumar; Ducroux, Laurent; Dupieux, Pascal; Dutta Majumdar, Mihir Ranjan; Dutta Majumdar, AK; Elia, Domenico; Emschermann, David Philip; Engel, Heiko; Erdal, Hege Austrheim; Espagnon, Bruno; Estienne, Magali Danielle; Esumi, Shinichi; Evans, David; Eyyubova, Gyulnara; Fabris, Daniela; Faivre, Julien; Falchieri, Davide; Fantoni, Alessandra; Fasel, Markus; Fearick, Roger Worsley; Fedunov, Anatoly; Fehlker, Dominik; Feldkamp, Linus; Felea, Daniel; Fenton-Olsen, Bo; Feofilov, Grigory; Fernandez Tellez, Arturo; Ferretti, Alessandro; Ferretti, Roberta; Figiel, Jan; Figueredo, Marcel; Filchagin, Sergey; Finogeev, Dmitry; Fionda, Fiorella; Fiore, Enrichetta Maria; Floris, Michele; Foertsch, Siegfried Valentin; Foka, Panagiota; Fokin, Sergey; Fragiacomo, Enrico; Frankenfeld, Ulrich Michael; Fuchs, Ulrich; Furget, Christophe; Fusco Girard, Mario; Gaardhoje, Jens Joergen; Gagliardi, Martino; Gago, Alberto; Gallio, Mauro; Gangadharan, Dhevan Raja; Ganoti, Paraskevi; Garabatos, Jose; Garcia-Solis, Edmundo; Garishvili, Irakli; Gerhard, Jochen; Germain, Marie; Geuna, Claudio; Gheata, Andrei George; Gheata, Mihaela; Ghidini, Bruno; Ghosh, Premomoy; Gianotti, Paola; Girard, Martin Robert; Giubellino, Paolo; Gladysz-Dziadus, Ewa; Glassel, Peter; Gomez, Ramon; Gonschior, Alexey; Gonzalez Ferreiro, Elena; Gonzalez-Trueba, Laura Helena; Gonzalez-Zamora, Pedro; Gorbunov, Sergey; Goswami, Ankita; Gotovac, Sven; Grabski, Varlen; Graczykowski, Lukasz Kamil; Grajcarek, Robert; Grelli, Alessandro; Grigoras, Costin; Grigoras, Alina Gabriela; Grigoriev, Vladislav; Grigoryan, Ara; Grigoryan, Smbat; Grinyov, Boris; Grion, Nevio; Gros, Philippe; Grosse-Oetringhaus, Jan Fiete; Grossiord, Jean-Yves; Grosso, Raffaele; Guber, Fedor; Guernane, Rachid; Guerra Gutierrez, Cesar; Guerzoni, Barbara; Guilbaud, Maxime Rene Joseph; Gulbrandsen, Kristjan Herlache; Gunji, Taku; Gupta, Anik; Gupta, Ramni; Gutbrod, Hans; Haaland, Oystein Senneset; Hadjidakis, Cynthia Marie; Haiduc, Maria; Hamagaki, Hideki; Hamar, Gergoe; Han, Byounghee; Hanratty, Luke David; Hansen, Alexander; Harmanova, Zuzana; Harris, John William; Hartig, Matthias; Hasegan, Dumitru; Hatzifotiadou, Despoina; Hayrapetyan, Arsen; Heckel, Stefan Thomas; Heide, Markus Ansgar; Helstrup, Haavard; Herghelegiu, Andrei Ionut; Herrera Corral, Gerardo Antonio; Herrmann, Norbert; Hess, Benjamin Andreas; Hetland, Kristin Fanebust; Hicks, Bernard; Hille, Per Thomas; Hippolyte, Boris; Horaguchi, Takuma; Hori, Yasuto; Hristov, Peter Zahariev; Hrivnacova, Ivana; Huang, Meidana; Humanic, Thomas; Hwang, Dae Sung; Ichou, Raphaelle; Ilkaev, Radiy; Ilkiv, Iryna; Inaba, Motoi; Incani, Elisa; Innocenti, Gian Michele; Innocenti, Pier Giorgio; Ippolitov, Mikhail; Irfan, Muhammad; Ivan, Cristian George; Ivanov, Vladimir; Ivanov, Marian; Ivanov, Andrey; Ivanytskyi, Oleksii; Jacholkowski, Adam Wlodzimierz; Jacobs, Peter; Jang, Haeng Jin; Jangal, Swensy Gwladys; Janik, Malgorzata Anna; Janik, Rudolf; Jayarathna, Sandun; Jena, Satyajit; Jha, Deeptanshu Manu; Jimenez Bustamante, Raul Tonatiuh; Jirden, Lennart; Jones, Peter Graham; Jung, Hyung Taik; Jusko, Anton; Kaidalov, Alexei; Kakoyan, Vanik; Kalcher, Sebastian; Kalinak, Peter; Kalliokoski, Tuomo Esa Aukusti; Kalweit, Alexander Philipp; Kanaki, Kalliopi; Kang, Ju Hwan; Kaplin, Vladimir; Karasu Uysal, Ayben; Karavichev, Oleg; Karavicheva, Tatiana; Karpechev, Evgeny; Kazantsev, Andrey; Kebschull, Udo Wolfgang; Keidel, Ralf; Khan, Palash; Khan, Mohisin Mohammed; Khan, Shuaib Ahmad; Khanzadeev, Alexei; Kharlov, Yury; Kileng, Bjarte; Kim, Do Won; Kim, Mimae; Kim, Minwoo; Kim, Seon Hee; Kim, Dong Jo; Kim, Se Yong; Kim, Jonghyun; Kim, Jin Sook; Kim, Beomkyu; Kim, Taesoo; Kirsch, Stefan; Kisel, Ivan; Kiselev, Sergey; Kisiel, Adam Ryszard; Klay, Jennifer Lynn; Klein, Jochen; Klein-Bosing, Christian; Kliemant, Michael; Kluge, Alexander; Knichel, Michael Linus; Knospe, Anders Garritt; Koch, Kathrin; Kohler, Markus; Kolojvari, Anatoly; Kondratiev, Valery; Kondratyeva, Natalia; Konevskih, Artem; Korneev, Andrey; Kour, Ravjeet; Kowalski, Marek; Kox, Serge; Koyithatta Meethaleveedu, Greeshma; Kral, Jiri; Kralik, Ivan; Kramer, Frederick; Kraus, Ingrid Christine; Krawutschke, Tobias; Krelina, Michal; Kretz, Matthias; Krivda, Marian; Krizek, Filip; Krus, Miroslav; Kryshen, Evgeny; Krzewicki, Mikolaj; Kucheriaev, Yury; Kuhn, Christian Claude; Kuijer, Paul; Kulakov, Igor; Kumar, Jitendra; Kurashvili, Podist; Kurepin, AB; Kurepin, A; Kuryakin, Alexey; Kushpil, Vasily; Kushpil, Svetlana; Kvaerno, Henning; Kweon, Min Jung; Kwon, Youngil; Ladron de Guevara, Pedro; Lakomov, Igor; Langoy, Rune; La Pointe, Sarah Louise; Lara, Camilo Ernesto; Lardeux, Antoine Xavier; La Rocca, Paola; Lazzeroni, Cristina; Lea, Ramona; Le Bornec, Yves; Lechman, Mateusz; Lee, Sung Chul; Lee, Ki Sang; Lee, Graham Richard; Lefevre, Frederic; Lehnert, Joerg Walter; Leistam, Lars; Lenhardt, Matthieu Laurent; Lenti, Vito; Leon, Hermes; Leoncino, Marco; Leon Monzon, Ildefonso; Leon Vargas, Hermes; Levai, Peter; Lien, Jorgen; Lietava, Roman; Lindal, Svein; Lindenstruth, Volker; Lippmann, Christian; Lisa, Michael Annan; Liu, Lijiao; Loenne, Per-Ivar; Loggins, Vera; Loginov, Vitaly; Lohn, Stefan Bernhard; Lohner, Daniel; Loizides, Constantinos; Loo, Kai Krister; Lopez, Xavier Bernard; Lopez Torres, Ernesto; Lovhoiden, Gunnar; Lu, Xianguo; Luettig, Philipp; Lunardon, Marcello; Luo, Jiebin; Luparello, Grazia; Luquin, Lionel; Luzzi, Cinzia; Ma, Rongrong; Ma, Ke; Madagodahettige-Don, Dilan Minthaka; Maevskaya, Alla; Mager, Magnus; Mahapatra, Durga Prasad; Maire, Antonin; Malaev, Mikhail; Maldonado Cervantes, Ivonne Alicia; Malinina, Ludmila; Mal'Kevich, Dmitry; Malzacher, Peter; Mamonov, Alexander; Manceau, Loic Henri Antoine; Mangotra, Lalit Kumar; Manko, Vladislav; Manso, Franck; Manzari, Vito; Mao, Yaxian; Marchisone, Massimiliano; Mares, Jiri; Margagliotti, Giacomo Vito; Margotti, Anselmo; Marin, Ana Maria; Marin Tobon, Cesar Augusto; Markert, Christina; Martashvili, Irakli; Martinengo, Paolo; Martinez, Mario Ivan; Martinez Davalos, Arnulfo; Martinez Garcia, Gines; Martynov, Yevgen; Mas, Alexis Jean-Michel; Masciocchi, Silvia; Masera, Massimo; Masoni, Alberto; Massacrier, Laure Marie; Mastromarco, Mario; Mastroserio, Annalisa; Matthews, Zoe Louise; Matyja, Adam Tomasz; Mayani, Daniel; Mayer, Christoph; Mazer, Joel; Mazzoni, Alessandra Maria; Meddi, Franco; Menchaca-Rocha, Arturo Alejandro; Mercado Perez, Jorge; Meres, Michal; Miake, Yasuo; Milano, Leonardo; Milosevic, Jovan; Mischke, Andre; Mishra, Aditya Nath; Miskowiec, Dariusz; Mitu, Ciprian Mihai; Mlynarz, Jocelyn; Mohanty, Bedangadas; Mohanty, Ajit Kumar; Molnar, Levente; Montano Zetina, Luis Manuel; Monteno, Marco; Montes, Esther; Moon, Taebong; Morando, Maurizio; Moreira De Godoy, Denise Aparecida; Moretto, Sandra; Morsch, Andreas; Muccifora, Valeria; Mudnic, Eugen; Muhuri, Sanjib; Mukherjee, Maitreyee; Muller, Hans; Munhoz, Marcelo; Musa, Luciano; Musso, Alfredo; Nandi, Basanta Kumar; Nania, Rosario; Nappi, Eugenio; Nattrass, Christine; Naumov, Nikolay; Navin, Sparsh; Nayak, Tapan Kumar; Nazarenko, Sergey; Nazarov, Gleb; Nedosekin, Alexander; Nicassio, Maria; Niculescu, Mihai; Nielsen, Borge Svane; Niida, Takafumi; Nikolaev, Sergey; Nikolic, Vedran; Nikulin, Sergey; Nikulin, Vladimir; Nilsen, Bjorn Steven; Nilsson, Mads Stormo; Noferini, Francesco; Nomokonov, Petr; Nooren, Gerardus; Novitzky, Norbert; Nyanin, Alexandre; Nyatha, Anitha; Nygaard, Casper; Nystrand, Joakim Ingemar; Ochirov, Alexander; Oeschler, Helmut Oskar; Oh, Saehanseul; Oh, Sun Kun; Oleniacz, Janusz; Oppedisano, Chiara; Ortiz Velasquez, Antonio; Ortona, Giacomo; Oskarsson, Anders Nils Erik; Ostrowski, Piotr Krystian; Otwinowski, Jacek Tomasz; Oyama, Ken; Ozawa, Kyoichiro; Pachmayer, Yvonne Chiara; Pachr, Milos; Padilla, Fatima; Pagano, Paola; Paic, Guy; Painke, Florian; Pajares, Carlos; Pal, S; Pal, Susanta Kumar; Palaha, Arvinder Singh; Palmeri, Armando; Papikyan, Vardanush; Pappalardo, Giuseppe; Park, Woo Jin; Passfeld, Annika; Pastircak, Blahoslav; Patalakha, Dmitri Ivanovich; Paticchio, Vincenzo; Pavlinov, Alexei; Pawlak, Tomasz Jan; Peitzmann, Thomas; Pereira Da Costa, Hugo Denis Antonio; Pereira De Oliveira Filho, Elienos; Peresunko, Dmitri; Perez Lara, Carlos Eugenio; Perez Lezama, Edgar; Perini, Diego; Perrino, Davide; Peryt, Wiktor Stanislaw; Pesci, Alessandro; Peskov, Vladimir; Pestov, Yury; Petracek, Vojtech; Petran, Michal; Petris, Mariana; Petrov, Plamen Rumenov; Petrovici, Mihai; Petta, Catia; Piano, Stefano; Piccotti, Anna; Pikna, Miroslav; Pillot, Philippe; Pinazza, Ombretta; Pinsky, Lawrence; Pitz, Nora; Piyarathna, Danthasinghe; Ploskon, Mateusz Andrzej; Pluta, Jan Marian; Pocheptsov, Timur; Pochybova, Sona; Podesta Lerma, Pedro Luis Manuel; Poghosyan, Martin; Polak, Karel; Polichtchouk, Boris; Pop, Amalia; Porteboeuf-Houssais, Sarah; Pospisil, Vladimir; Potukuchi, Baba; Prasad, Sidharth Kumar; Preghenella, Roberto; Prino, Francesco; Pruneau, Claude Andre; Pshenichnov, Igor; Puchagin, Sergey; Puddu, Giovanna; Pujol Teixido, Jordi; Pulvirenti, Alberto; Punin, Valery; Putis, Marian; Putschke, Jorn Henning; Quercigh, Emanuele; Qvigstad, Henrik; Rachevski, Alexandre; Rademakers, Alphonse; Radomski, Sylwester; Raiha, Tomi Samuli; Rak, Jan; Rakotozafindrabe, Andry Malala; Ramello, Luciano; Ramirez Reyes, Abdiel; Raniwala, Sudhir; Raniwala, Rashmi; Rasanen, Sami Sakari; Rascanu, Bogdan Theodor; Rathee, Deepika; Read, Kenneth Francis; Real, Jean-Sebastien; Redlich, Krzysztof; Reichelt, Patrick; Reicher, Martijn; Renfordt, Rainer Arno Ernst; Reolon, Anna Rita; Reshetin, Andrey; Rettig, Felix Vincenz; Revol, Jean-Pierre; Reygers, Klaus Johannes; Riccati, Lodovico; Ricci, Renato Angelo; Richert, Tuva; Richter, Matthias Rudolph; Riedler, Petra; Riegler, Werner; Riggi, Francesco; Rodrigues Fernandes Rabacal, Bartolomeu; Rodriguez Cahuantzi, Mario; Rodriguez Manso, Alis; Roed, Ketil; Rohr, David; Rohrich, Dieter; Romita, Rosa; Ronchetti, Federico; Rosnet, Philippe; Rossegger, Stefan; Rossi, Andrea; Roy, Christelle Sophie; Roy, Pradip Kumar; Rubio Montero, Antonio Juan; Rui, Rinaldo; Ryabinkin, Evgeny; Rybicki, Andrzej; Sadovsky, Sergey; Safarik, Karel; Sahoo, Raghunath; Sahu, Pradip Kumar; Saini, Jogender; Sakaguchi, Hiroaki; Sakai, Shingo; Sakata, Dosatsu; Salgado, Carlos Albert; Salzwedel, Jai; Sambyal, Sanjeev Singh; Samsonov, Vladimir; Sanchez Castro, Xitzel; Sandor, Ladislav; Sandoval, Andres; Sano, Satoshi; Sano, Masato; Santo, Rainer; Santoro, Romualdo; Sarkamo, Juho Jaako; Scapparone, Eugenio; Scarlassara, Fernando; Scharenberg, Rolf Paul; Schiaua, Claudiu Cornel; Schicker, Rainer Martin; Schmidt, Christian Joachim; Schmidt, Hans Rudolf; Schreiner, Steffen; Schuchmann, Simone; Schukraft, Jurgen; Schutz, Yves Roland; Schwarz, Kilian Eberhard; Schweda, Kai Oliver; Scioli, Gilda; Scomparin, Enrico; Scott, Rebecca; Scott, Patrick Aaron; Segato, Gianfranco; Selyuzhenkov, Ilya; Senyukov, Serhiy; Seo, Jeewon; Serci, Sergio; Serradilla, Eulogio; Sevcenco, Adrian; Shabetai, Alexandre; Shabratova, Galina; Shahoyan, Ruben; Sharma, Natasha; Sharma, Satish; Sharma, Rohini; Shigaki, Kenta; Shimomura, Maya; Shtejer, Katherin; Sibiriak, Yury; Siciliano, Melinda; Sicking, Eva; Siddhanta, Sabyasachi; Siemiarczuk, Teodor; Silvermyr, David Olle Rickard; Silvestre, catherine; Simatovic, Goran; Simonetti, Giuseppe; Singaraju, Rama Narayana; Singh, Ranbir; Singha, Subhash; Singhal, Vikas; Sinha, Tinku; Sinha, Bikash; Sitar, Branislav; Sitta, Mario; Skaali, Bernhard; Skjerdal, Kyrre; Smakal, Radek; Smirnov, Nikolai; Snellings, Raimond; Sogaard, Carsten; Soltz, Ron Ariel; Son, Hyungsuk; Song, Myunggeun; Song, Jihye; Soos, Csaba; Soramel, Francesca; Sputowska, Iwona; Spyropoulou-Stassinaki, Martha; Srivastava, Brijesh Kumar; Stachel, Johanna; Stan, Ionel; Stan, Ionel; Stefanek, Grzegorz; Steinbeck, Timm Morten; Steinpreis, Matthew; Stenlund, Evert Anders; Steyn, Gideon Francois; Stiller, Johannes Hendrik; Stocco, Diego; Stolpovskiy, Mikhail; Strabykin, Kirill; Strmen, Peter; Suaide, Alexandre Alarcon do Passo; Subieta Vasquez, Martin Alfonso; Sugitate, Toru; Suire, Christophe Pierre; Sukhorukov, Mikhail; Sultanov, Rishat; Sumbera, Michal; Susa, Tatjana; Szanto de Toledo, Alejandro; Szarka, Imrich; Szczepankiewicz, Adam; Szostak, Artur Krzysztof; Szymanski, Maciej; Takahashi, Jun; Tapia Takaki, Daniel Jesus; Tauro, Arturo; Tejeda Munoz, Guillermo; Telesca, Adriana; Terrevoli, Cristina; Thader, Jochen Mathias; Thomas, Deepa; Tieulent, Raphael Noel; Timmins, Anthony; Tlusty, David; Toia, Alberica; Torii, Hisayuki; Toscano, Luca; Truesdale, David Christopher; Trzaska, Wladyslaw Henryk; Tsuji, Tomoya; Tumkin, Alexandr; Turrisi, Rosario; Tveter, Trine Spedstad; Ulery, Jason Glyndwr; Ullaland, Kjetil; Ulrich, Jochen; Uras, Antonio; Urban, Jozef; Urciuoli, Guido Marie; Usai, Gianluca; Vajzer, Michal; Vala, Martin; Valencia Palomo, Lizardo; Vallero, Sara; van der Kolk, Naomi; Vande Vyvre, Pierre; van Leeuwen, Marco; Vannucci, Luigi; Vargas, Aurora Diozcora; Varma, Raghava; Vasileiou, Maria; Vasiliev, Andrey; Vechernin, Vladimir; Veldhoen, Misha; Venaruzzo, Massimo; Vercellin, Ermanno; Vergara, Sergio; Vernet, Renaud; Verweij, Marta; Vickovic, Linda; Viesti, Giuseppe; Vikhlyantsev, Oleg; Vilakazi, Zabulon; Villalobos Baillie, Orlando; Vinogradov, Alexander; Vinogradov, Leonid; Vinogradov, Yury; Virgili, Tiziano; Viyogi, Yogendra; Vodopianov, Alexander; Voloshin, Kirill; Voloshin, Sergey; Volpe, Giacomo; von Haller, Barthelemy; Vranic, Danilo; Øvrebekk, Gaute; Vrlakova, Janka; Vulpescu, Bogdan; Vyushin, Alexey; Wagner, Vladimir; Wagner, Boris; Wan, Renzhuo; Wang, Mengliang; Wang, Dong; Wang, Yifei; Wang, Yaping; Watanabe, Kengo; Weber, Michael; Wessels, Johannes; Westerhoff, Uwe; Wiechula, Jens; Wikne, Jon; Wilde, Martin Rudolf; Wilk, Grzegorz Andrzej; Wilk, Alexander; Williams, Crispin; Windelband, Bernd Stefan; Xaplanteris Karampatsos, Leonidas; Yaldo, Chris G; Yamaguchi, Yorito; Yang, Hongyan; Yang, Shiming; Yasnopolsky, Stanislav; Yi, JunGyu; Yin, Zhongbao; Yoo, In-Kwon; Yoon, Jongik; Yu, Weilin; Yuan, Xianbao; Yushmanov, Igor; Zach, Cenek; Zampolli, Chiara; Zaporozhets, Sergey; Zarochentsev, Andrey; Zavada, Petr; Zaviyalov, Nikolai; Zbroszczyk, Hanna Paulina; Zelnicek, Pierre; Zgura, Sorin Ion; Zhalov, Mikhail; Zhang, Xiaoming; Zhang, Haitao; Zhou, Fengchu; Zhou, Daicui; Zhou, You; Zhu, Jianhui; Zhu, Jianlin; Zhu, Xiangrong; Zichichi, Antonino; Zimmermann, Alice; Zinovjev, Gennady; Zoccarato, Yannick Denis; Zynovyev, Mykhaylo; Zyzak, Maksym

    2012-09-18

    Measurements of the sphericity of primary charged particles in minimum bias proton--proton collisions at $\\sqrt{s}$=0.9, 2.76 and 7 TeV with the ALICE detector at the LHC are presented. The observable is linearized to be collinear safe and is measured in the plane perpendicular to the beam direction using primary charged tracks with $p_{\\rm T}\\geq0.5$ GeV/c in $|\\eta|\\leq0.8$. The mean sphericity as a function of the charged particle multiplicity at mid-rapidity ($N_{\\rm ch}$) is reported for events with different $p_{\\rm T}$ scales ("soft" and "hard") defined by the transverse momentum of the leading particle. In addition, the mean charged particle transverse momentum versus multiplicity is presented for the different event classes, and the sphericity distributions in bins of multiplicity are presented. The data are compared with calculations of standard Monte Carlo event generators. The transverse sphericity is found to grow with multiplicity at all collision energies, with a steeper rise at low $N_{\\rm ch}...

  12. Experimental verification of theoretical equations for acoustic radiation force on compressible spherical particles in traveling waves

    Science.gov (United States)

    Johnson, Kennita A.; Vormohr, Hannah R.; Doinikov, Alexander A.; Bouakaz, Ayache; Shields, C. Wyatt; López, Gabriel P.; Dayton, Paul A.

    2016-05-01

    Acoustophoresis uses acoustic radiation force to remotely manipulate particles suspended in a host fluid for many scientific, technological, and medical applications, such as acoustic levitation, acoustic coagulation, contrast ultrasound imaging, ultrasound-assisted drug delivery, etc. To estimate the magnitude of acoustic radiation forces, equations derived for an inviscid host fluid are commonly used. However, there are theoretical predictions that, in the case of a traveling wave, viscous effects can dramatically change the magnitude of acoustic radiation forces, which make the equations obtained for an inviscid host fluid invalid for proper estimation of acoustic radiation forces. To date, experimental verification of these predictions has not been published. Experimental measurements of viscous effects on acoustic radiation forces in a traveling wave were conducted using a confocal optical and acoustic system and values were compared with available theories. Our results show that, even in a low-viscosity fluid such as water, the magnitude of acoustic radiation forces is increased manyfold by viscous effects in comparison with what follows from the equations derived for an inviscid fluid.

  13. Active particle control experiments and critical particle flux discriminating between the wall pumping and fuelling in the compact plasma wall interaction device CPD spherical tokamak

    Science.gov (United States)

    Zushi, H.; Hirooka, Y.; Bhattacharyay, R.; Sakamoto, M.; Nakashima, Y.; Yoshinaga, T.; Higashizono, Y.; Hanada, K.; Nishino, N.; Yoshida, N.; Tokunaga, K.; Kado, S.; Shikama, T.; Kawasaki, S.; Okamoto, K.; Miyazaki, T.; Honma, H.; Sato, K. N.; Nakamura, K.; Idei, H.; Hasegawa, M.; Nakashima, H.; Higashijima, A.

    2009-05-01

    Two approaches associated with wall recycling have been performed in a small spherical tokamak device CPD (compact plasma wall interaction experimental device), that is, (1) demonstration of active particle recycling control, namely, 'active wall pumping' using a rotating poloidal limiter whose surface is continuously gettered by lithium and (2) a basic study of the key parameters which discriminates between 'wall pumping and fuelling'. For the former, active control of 'wall pumping' has been demonstrated during 50 kW RF current drive discharges whose pulse length is typically ~300 ms. Although the rotating limiter is located at the outer board, as soon as the rotating drum is gettered with lithium, hydrogen recycling measured with Hα spectroscopy decreases by about a factor of 3 not only near the limiter but also in the centre stack region. Also, the oxygen impurity level measured with O II spectroscopy is reduced by about a factor of 3. As a consequence of the reduced recycling and impurity level, RF driven current has nearly doubled at the same vertical magnetic field. For the latter, global plasma wall interaction with plasma facing components in the vessel is studied in a simple torus produced by electron cyclotron waves with Ip static gas balance (pressure measurement) without external pumping systems has been performed to investigate the role of particle flux on a transition of 'wall fuelling' to 'wall pumping'. It is found that a critical particle flux exists to discriminate between them. Beyond the critical value, a large fraction (~80%) of pressure drop ('wall pumping') is found, suggesting that almost all injected particles are retained in the wall. Below it, a significant pressure rise ('wall fuelling') is found, which indicates that particles are fuelled from the wall during/just after the discharge. Shot history effects (integrated particle recycling behaviour from the plasma facing surfaces) are seen on that the critical particle flux is reducing

  14. LIGHT PRESSURE: Theoretical study of the light pressure force acting on a spherical dielectric particle of an arbitrary size in the interference field of two plane monochromatic electromagnetic waves

    Science.gov (United States)

    Guzatov, D. V.; Gaida, L. S.; Afanas'ev, Anatolii A.

    2008-12-01

    The light pressure force acting on a spherical dielectric particle in the interference field of two plane monochromatic electromagnetic waves is studied in detail for different particle radii and angles of incidence of waves.

  15. Effect of ion implantation energy for the synthesis of Ge nanocrystals in SiN films with HfO2/SiO2 stack tunnel dielectrics for memory application

    Directory of Open Access Journals (Sweden)

    Gloux Florence

    2011-01-01

    Full Text Available Abstract Ge nanocrystals (Ge-NCs embedded in SiN dielectrics with HfO2/SiO2 stack tunnel dielectrics were synthesized by utilizing low-energy (≤5 keV ion implantation method followed by conventional thermal annealing at 800°C, the key variable being Ge+ ion implantation energy. Two different energies (3 and 5 keV have been chosen for the evolution of Ge-NCs, which have been found to possess significant changes in structural and chemical properties of the Ge+-implanted dielectric films, and well reflected in the charge storage properties of the Al/SiN/Ge-NC + SiN/HfO2/SiO2/Si metal-insulator-semiconductor (MIS memory structures. No Ge-NC was detected with a lower implantation energy of 3 keV at a dose of 1.5 × 1016 cm-2, whereas a well-defined 2D-array of nearly spherical and well-separated Ge-NCs within the SiN matrix was observed for the higher-energy-implanted (5 keV sample for the same implanted dose. The MIS memory structures implanted with 5 keV exhibits better charge storage and retention characteristics compared to the low-energy-implanted sample, indicating that the charge storage is predominantly in Ge-NCs in the memory capacitor. A significant memory window of 3.95 V has been observed under the low operating voltage of ± 6 V with good retention properties, indicating the feasibility of these stack structures for low operating voltage, non-volatile memory devices.

  16. Ultra-low voltage resistive switching of HfO2 buffered (001) epitaxial NiO films deposited on metal seed layers

    Science.gov (United States)

    Qiu, X. Y.; Wang, R. X.; Zhang, Z.; Wei, M. L.; Ji, H.; Chai, Y.; Zhou, F. C.; Dai, J. Y.; Zhang, T.; Li, L. T.; Meng, X. S.

    2017-10-01

    A set of (001) epitaxial NiO films were prepared on highly textured (001) Pt seed layers using magnetron sputtering, and their resistive switching performance was measured. Cube-to-cube epitaxial relationships of NiO(001)//Pt(001) and NiO[001]//Pt[001] were demonstrated. Current-voltage measurements revealed that the Ag/(001)NiO/(001)Pt capacitor structures exhibited stable bipolar switching behavior with an ON/OFF ratio of 20 and an endurance of over 5 × 103 cycles. Furthermore, inserting a HfO2 buffer layer between the NiO film and the Ag top electrode increased the ON/OFF ratio to more than 103 and reduced the SET/RESET voltage to below ±0.2 V. These enhancements are attributed to the differing filament growth mechanisms that occur in the NiO and HfO2 layers. The present work suggests that Ag/HfO2/(001)NiO/(001)Pt capacitor structures are a promising technology for next-generation, ultra-low voltage resistive switching memory.

  17. The impact of charge compensated and uncompensated strontium defects on the stabilization of the ferroelectric phase in HfO2

    Science.gov (United States)

    Materlik, Robin; Künneth, Christopher; Mikolajick, Thomas; Kersch, Alfred

    2017-08-01

    Different dopants with their specific dopant concentration can be utilized to produce ferroelectric HfO2 thin films. In this work, it is explored for Sr in a comprehensive first-principles study. Density functional calculations reveal structure, formation energy, and total energy of the Sr related defects in HfO2. We found the charge compensated defect with an associated oxygen vacancy SrHfVO to strongly favour the non-ferroelectric, tetragonal P42/mnc phase energetically. In contrast, the uncompensated defect without oxygen vacancy SrHf favours the ferroelectric, orthorhombic Pca21 phase. According to the formation energy, the uncompensated defect can form easily under oxygen rich conditions in the production process. Low oxygen partial pressure existing over the lifetime promotes the loss of oxygen leading to VO, and thus, the destabilization of the ferroelectric, orthorhombic Pca21 phase is accompanied by an increase of the leakage current. This study attempts to fundamentally explain the stabilization of the ferroelectric, orthorhombic Pca21 phase by doping.

  18. Lateral Distribution of Polycyclic Aromatic Hydrocarbons and Spherical Magnetic Particles within Soil Catenas of the Arable Watershed (Tver Region, Russia)

    Science.gov (United States)

    Koshovskii, Timur; Zhidkin, Andrei; Gennadiev, Alexander

    2015-04-01

    Polycyclic aromatic hydrocarbons (PAHs) are very dangerous substances because of their carcinogenic properties. It is important to know the features of PAHs transport and accumulation in soils, especially on agricultural lands. Unfortunately this scientific problem is studied not enough. It is known that predominantly PAHs in soils are sorbed on solid phase particles [2], so redistribution of PAHs should be carried out with transport of soil solid phase matter. For the purpose of assessment of connections between PAHs and soil solid phase transport the lateral distribution of PAHs and spherical magnetic particles (SMP) as tracers of soil solid phase migration has been compared. SMP is the component of fly ash which is used last two decades for quantitative assessment of soil erosion [1]. Studies were conducted in small watershed of south-taiga zone in European part of Russia in Tver region. The watershed has 53 ha, steep slopes, less 50, convex and convexo-concave shapes with ridges and runnels. The watershed lands were plowed up for the last 350-400 years until 1995 year. Predominant soils are Umbric Albeluvisols. Soil samples were selected at four soil catenas (30 points with average distance about 70 meters). Two catenas were on opposite slopes near the road, and other two catenas were located on the opposite slopes (250-400 m from the road). It is revealed that average concentration of PAHs in studied soils are 105 ng/g, and varies from 11 to 770 ng/g, with coefficient of variation 143%. Lateral distribution of PAHs and SMP differs within different catenas, because of various factors influence on PAHs concentrations: 1) amounts of PAHs income, depending on the distance from the source; 2) homogenization of PAHs concentrations within arable layer because of mixing the soil matter due to plowing; 3) vertical transport of PAHs in subarable layers is also connected with plowing and bioturbation; 4) rates of decomposition of PAHs in arable layer, depending on

  19. Influence of the oxygen concentration of atomic-layer-deposited HfO2 films on the dielectric property and interface trap density

    Science.gov (United States)

    Park, Jaehoo; Cho, Moonju; Kim, Seong Keun; Park, Tae Joo; Lee, Suk Woo; Hong, Sug Hun; Hwang, Cheol Seong

    2005-03-01

    The influence of the ozone concentration (160-370g/m3) during atomic layer deposition of HfO2-gate dielectrics on the dielectric performance of the films grown on Si was studied. Although ozone was effective in reducing the impurity concentration in the film compared to H2O, the higher concentration slightly deteriorated the dielectric performance. More importantly, the degradation in the interface trap property with increasing post-annealing temperature became more serious as the ozone concentration increased. Investigation of the interface states using x-ray photoelectron spectroscopy revealed that the excessive oxygen incorporated during the film growth made the interfacial sub-oxide species (SiO, Si2O3, and silicate) and SiO2 coordinate more with oxygen. This increased the interface trap density and degraded the interface properties.

  20. Voltage and oxide thickness dependent tunneling current density and tunnel resistivity model: Application to high-k material HfO2 based MOS devices

    Science.gov (United States)

    Maity, N. P.; Maity, Reshmi; Baishya, Srimanta

    2017-11-01

    In this paper presents a straightforward efficient investigation of tunneling current density for ultra thin oxide layer based metal-oxide-semiconductor (MOS) devices to realization the gate current as a function of applied potential and oxide thickness. Solutions to the Schrödinger's wave equation are evolved for the different potential energy regions of the MOS device considering appropriate effective mass for each region. For finding approximate mathematical solutions to linear differential equations using spatially changeable coefficients the Wentzel-Kramers-Brillouin (WKB) approximation technique is considered. A p-substrate based n-channel MOS device has been analyzed consisting of SiO2 material as the oxide dielectric along with high-k material HfO2. The tunnel resistivity is correspondingly assessed employing this tunneling current density model. Synopsys Technology Computer Aided Design (TCAD) tool results are employed to validate the analytical model. Tremendous agreements among the results are observed.

  1. A general result for the magnetoelastic response of isotropic suspensions of iron and ferrofluid particles in rubber, with applications to spherical and cylindrical specimens

    Science.gov (United States)

    Lefèvre, Victor; Danas, Kostas; Lopez-Pamies, Oscar

    2017-10-01

    This paper puts forth an approximate solution for the effective free-energy function describing the homogenized (or macroscopic) magnetoelastic response of magnetorheological elastomers comprised of non-Gaussian rubbers filled with isotropic suspensions of either iron or ferrofluid particles. The solution is general in that it applies to N = 2 and 3 space dimensions and any arbitrary (non-percolative) isotropic suspension of filler particles. By construction, it is exact in the limit of small deformations and moderate magnetic fields. For finite deformations and finite magnetic fields, its accuracy is demonstrated by means of direct comparisons with full-field simulations for two prominent cases: (i) isotropic suspensions of circular particles and (ii) isotropic suspensions of spherical particles. With the combined objectives of demonstrating the possible benefits of using ferrofluid particles in lieu of the more conventional iron particles as fillers and gaining insight into recent experimental results, the proposed homogenization-based constitutive model is deployed to generate numerical solutions for boundary-value problems of both fundamental and practical significance: those consisting of magnetorheological elastomer specimens of spherical and cylindrical shape that are immersed in air and subjected to a remotely applied uniform magnetic field. It is found that magnetorheological elastomers filled with ferrofluid particles can exhibit magnetostrictive capabilities far superior to those of magnetorheological elastomers filled with iron particles. The results also reveal that the deformation and magnetic fields are highly heterogenous within the specimens and strongly dependent on the shape of these, specially for magnetorheological elastomers filled with iron particles. From an applications perspective, this evidence makes it plain that attempts at designing magnetrostrictive devices based on magnetorheological elastomers need to be approached, in general, as

  2. Electrical Characteristics of the Uniaxial-Strained nMOSFET with a Fluorinated HfO2/SiON Gate Stack

    Directory of Open Access Journals (Sweden)

    Yung-Yu Chen

    2014-03-01

    Full Text Available The channel fluorine implantation (CFI process was integrated with the Si3N4 contact etch stop layer (SiN CESL uniaxial-strained n-channel metal-oxide-semiconductor field-effect transistor (nMOSFET with the hafnium oxide/silicon oxynitride (HfO2/SiON gate stack. The SiN CESL process clearly improves basic electrical performance, due to induced uniaxial tensile strain within the channel. However, further integrating of the CFI process with the SiN CESL-strained nMOSFET exhibits nearly identical transconductance, subthreshold swing, drain current, gate leakage and breakdown voltage, which indicates that the strain effect is not affected by the fluorine incorporation. Moreover, hydrogen will diffuse toward the interface during the SiN deposition, then passivate dangling bonds to form weak Si-H bonds, which is detrimental for channel hot electron stress (CHES. Before hydrogen diffusion, fluorine can be used to terminate oxygen vacancies and dangling bonds, which can create stronger Hf-F and Si-F bonds to resist consequent stress. Accordingly, the reliability of constant voltage stress (CVS and CHES for the SiN CESL uniaxial-strained nMOSFET can be further improved by the fluorinated HfO2/SiON using the CFI process. Nevertheless, the nMOSFET with either the SiN CESL or CFI process exhibits less charge detrapping, which means that a greater part of stress-induced charges would remain in the gate stack after nitrogen (SiN CESL or fluorine (CFI incorporation.

  3. Bariatric Arterial Embolization with Non-spherical Polyvinyl Alcohol Particles for Ghrelin Suppression in a Swine Model.

    Science.gov (United States)

    Kim, Jae Min; Kim, Man-Deuk; Han, Kichang; Muqmiroh, Lailatul; Kim, Seung Up; Kim, Gyoung Min; Kwon, Joonho; Park, Sung Il; Won, Jong Yun; Lee, Do Yun

    2017-05-01

    To evaluate the effect of bariatric arterial embolization (BAE) with non-spherical polyvinyl alcohol (PVA) particles on systemic ghrelin levels, weight change, and gastric ulceration risk in a swine model. From March 2014 to February 2015, ten healthy swine were used in the study (mean weight 31.5 kg; range 24.0-41.5 kg). The animals were randomly assigned to two groups: the embolized group (n = 5) in which BAE was performed and the control group (n = 5). In the embolized group, BAE was performed by selectively infusing 150-250 or 50-150 μm PVA into the gastric arteries that supplied the fundus of the stomach. In the control group, a sham procedure was performed with saline infusion. Plasma ghrelin levels were prospectively obtained at baseline and every 2 weeks thereafter. Endoscopy was performed 3 weeks after BAE to see whether any gastric ulcer occurred. To determine the durability of the occluded arteries, repeated celiac trunk angiography was performed 8 weeks after BAE. Then, all the swine were killed and necropsies were performed. The mean post-procedure ghrelin value decreased by 370.0 pg/mL in the embolized group at week 3 (mean 536.0 ± 334.3 pg/mL) and week 5 (mean 515.0 ± 150.0 pg/mL, p ghrelin levels were not significantly decreased between the embolized and control groups. There was a significant body weight change as follows: 35.1 ± 9.5 to 46.6 ± 15.7 kg and 31.8 ± 5.8 to 41.2 ± 6.6 kg at baseline and endpoint in the control and embolized groups, respectively (p ghrelin levels in embolized animals, but levels are not significantly different compared to controls. Stomach ulcerations were identified in 60% of the embolized animals.

  4. Improvement in negative bias illumination stress stability of In–Ga–Zn–O thin film transistors using HfO2 gate insulators by controlling atomic-layer-deposition conditions

    Science.gov (United States)

    Na, So-Yeong; Kim, Yeo-Myeong; Yoon, Da-Jeong; Yoon, Sung-Min

    2017-12-01

    The effects of atomic layer deposition (ALD) conditions for the HfO2 gate insulators (GI) on the device characteristics of the InGaZnO (IGZO) thin film transistors (TFTs) were investigated when the ALD temperature and Hf precursor purge time were varied to 200, 225, and 250 °C, and 15 and 30 s, respectively. The HfO2 thin films showed low leakage current density of 10‑8 A cm‑2, high dielectric constant of over 20, and smooth surface roughness at all ALD conditions. The IGZO TFTs using the HfO2 GIs showed good device characteristics such as a saturation mobility as high as 11 cm2 V‑1 s‑1, a subthreshold swing as low as 0.10 V/dec, and all the devices could be operated at a gate voltage as low as  ±3 V. While there were no marked differences in transfer characteristics and PBS stabilities among the fabricated devices, the NBIS instabilities could be improved by increasing the ALD temperature for the formation of HfO2 GIs by reducing the oxygen vacancies within the IGZO channel.

  5. Ziegler-Natta Catalyst Based on MgCl₂/Clay/ID/TiCl₄ for the Synthesis of Spherical Particles of Polypropylene Nanocomposites.

    Science.gov (United States)

    Cardoso, Renata da Silva; Oliveira, Jaqueline da Silva; Ramis, Luciana Bortolin; Marques, Maria de Fátima V

    2018-07-01

    In the present work, we have designed MgCl2/clay/internal donor (ID)/TiCl4 based bisupported Ziegler-Natta catalysts containing varying amounts of organoclay (montmorillonite) in order to synthesize spherical particles of polypropylene/clay nanocomposites (PCN). The organoclay was introduced into the catalyst support formulation and PCN was obtained using the in situ polymerization technique. Decreasing the reaction time, it was possible to obtain nanocomposites with high concentrations of clay (masterbatches). Micrographs of SEM confirmed the spherical morphology of the catalysts. In addition, XRD patterns show that the active sites for polymerization were inserted in the clay galleries. The catalytic performance was evaluated in slurry propylene polymerization using triethylaluminium as cocatalyst and silane as external electron donor at 70 °C, 4 bar, and different reaction times. The PCNs obtained containing different clay amounts were characterized by X-ray diffraction, thermal analyses, transmission electronic microscopy, and extractables in heptane. The results revealed that the synthesized PP/clay particles were also spherical showing that the morphological control is possible even using catalysts containing high amounts of clay. The PCN presented high degradation temperature (459 °C). The XRD peak related to the clay interlamellar distance has shifted to lower angles, and TEM images confirmed the formation of exfoliated/intercalated clay on the PP matrix and absence of microparticles of clay.

  6. Bariatric Arterial Embolization with Non-spherical Polyvinyl Alcohol Particles for Ghrelin Suppression in a Swine Model

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jae Min; Kim, Man-Deuk, E-mail: mdkim@yuhs.ac; Han, Kichang; Muqmiroh, Lailatul [Yonsei University College of Medicine, Department of Radiology, Research Institute of Radiological Science, Severance Hospital (Korea, Republic of); Kim, Seung Up [Yonsei University College of Medicine, Department of Internal Medicine, Severance Hospital (Korea, Republic of); Kim, Gyoung Min; Kwon, Joonho; Park, Sung Il; Won, Jong Yun; Lee, Do Yun [Yonsei University College of Medicine, Department of Radiology, Research Institute of Radiological Science, Severance Hospital (Korea, Republic of)

    2017-05-15

    PurposeTo evaluate the effect of bariatric arterial embolization (BAE) with non-spherical polyvinyl alcohol (PVA) particles on systemic ghrelin levels, weight change, and gastric ulceration risk in a swine model.Materials and MethodsFrom March 2014 to February 2015, ten healthy swine were used in the study (mean weight 31.5 kg; range 24.0–41.5 kg). The animals were randomly assigned to two groups: the embolized group (n = 5) in which BAE was performed and the control group (n = 5). In the embolized group, BAE was performed by selectively infusing 150–250 or 50–150 μm PVA into the gastric arteries that supplied the fundus of the stomach. In the control group, a sham procedure was performed with saline infusion. Plasma ghrelin levels were prospectively obtained at baseline and every 2 weeks thereafter. Endoscopy was performed 3 weeks after BAE to see whether any gastric ulcer occurred. To determine the durability of the occluded arteries, repeated celiac trunk angiography was performed 8 weeks after BAE. Then, all the swine were killed and necropsies were performed.ResultsThe mean post-procedure ghrelin value decreased by 370.0 pg/mL in the embolized group at week 3 (mean 536.0 ± 334.3 pg/mL) and week 5 (mean 515.0 ± 150.0 pg/mL, p < 0.05) relative to baseline (880.0 ± 559.5 pg/mL), respectively, but ghrelin levels were not significantly decreased between the embolized and control groups. There was a significant body weight change as follows: 35.1 ± 9.5 to 46.6 ± 15.7 kg and 31.8 ± 5.8 to 41.2 ± 6.6 kg at baseline and endpoint in the control and embolized groups, respectively (p < 0.05). However, the difference between groups was not significant at endpoint. In the embolized group, ulcerations were identified in three animals (60%) and the recanalization of the embolized arteries was noted on follow-up angiography in three animals (60%), respectively.ConclusionBAE with PVA particles can transiently suppress ghrelin

  7. Evaluation of AlGaN/GaN metal-oxide-semicondutor high-electron mobility transistors with plasma-enhanced atomic layer deposition HfO2/AlN date dielectric for RF power applications

    Science.gov (United States)

    Chiu, Yu Sheng; Luc, Quang Ho; Lin, Yueh Chin; Chien Huang, Jui; Dee, Chang Fu; Yeop Majlis, Burhanuddin; Chang, Edward Yi

    2017-09-01

    A plasma enhanced atomic layer deposition (PEALD) HfO2/AlN dielectric stack was used as the gate dielectric for AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors (MOS-HEMTs) for high-frequency power device applications. The capacitance-voltage (C-V) curves of the HfO2/AlN/GaN MOS capacitor (MOSCAP) showed a small frequency dispersion along with a very small hysteresis (˜50 mV). Moreover, the interface trap density (D it) was calculated to be 2.7 × 1011 cm-2 V-1 s-1 at 150 °C. Using PEALD-AlN as the interfacial passivation layer (IPL), the drain current of the HfO2/AlN MOS-HEMTs increased by about 46% and the gate leakage current decreased by six orders of magnitude as compared with those of the conventional Schottky gate AlGaN/GaN HEMTs processed using the same epitaxial wafer. The 0.3-µm-gate-length HfO2/AlN/AlGaN/GaN MOS-HEMTs demonstrated a 2.88 W/mm output power, a 23 dB power gain, a 30.2% power-added efficiency at 2.4 GHz, and an improved device linearity as compared with the conventional AlGaN/GaN HEMTs. The third-order intercept point at the output (OIP3) of the MOS-HEMTs was 28.4 as compared with that of 26.5 for the conventional GaN HEMTs. Overall, the MOS-HEMTs with a HfO2/AlN gate stack showed good potential for high-linearity RF power device applications.

  8. The Effects of a Constant Bias Force on the Dynamics of a Periodically Forced Spherical Particle in a Newtonian Fluid at Low Reynolds Numbers

    Science.gov (United States)

    Madhukar, K.; Ramamohan, T. R.; Shivakumara, I. S.

    2010-09-01

    We make use of the formulation developed by Lovalenti and Brady [1] for the hydrodynamic force acting upon a spherical particle undergoing arbitrary time dependent motion in an arbitrary time dependent uniform flow field at low Reynolds numbers, to derive an expression for the effects of a constant bias force acting on a periodically forced rigid spherical particle in a Newtonian fluid. We use Newton's second law to relate the total force acting on the particle to the motion of the particle. The total force is given by: Total force = Fext+FH, where, Fext is the external force inclusive of both the periodic force and the constant bias force. FH is the hydrodynamic force derived by Lovalenti and Brady [1] including both unsteady and convective inertia. The equation derived contains a nonlinear history term and is nonlinear. This equation is solved numerically using an adaptive step size Runge—Kutta scheme. We obtain several phase plots (plots between particle displacement and particle velocity), which show the effects of low Reynolds numbers, the periodic force and the effects of the constant bias force on the particle motion. It is observed that at low magnitudes of the periodic forcing the external constant force dominates and the particle moves along the direction of the external constant force. As we increase the magnitude of the periodic forcing, the periodic force is seen to dominate and the particle is seen to oscillate along a mean position with a slight drift along the direction of the periodic force and the external constant force, when they are imposed in the same direction. However the motion of the particle becomes more complicated when the directions of the periodic forcing and external constant force are opposite to each other. We also observe a reflection in phase space when the directions of both the forces are reversed. The phase plots typically are of a half sinusoidal, sinusoidal and a coiled (solenoidal) pattern. These plots include the effects

  9. Calculation of effective electromagnetic parameters of multi-needle zinc oxide whisker based on equivalent spherical particle and strong fluctuation theory

    Science.gov (United States)

    Zhao, Yu-Chen; Liu, Jiang-Fan; Song, Zhong-Guo; Xi, Xiao-Li

    2014-12-01

    Multi-needle zinc oxide whisker (M-ZnOw) includes tetrapod-needle ZnOw (T-ZnOw), flower-shaped ZnOw, and other similar ZnOw architectures. The unique three-dimensional (3D) and multi-needle-shaped structures give the special performance of M-ZnOw, but make it difficult to calculate the effective electromagnetic parameters of M-ZnOw composites. In this paper, based on the equivalent spherical particle and the strong fluctuation theory, three different closed-form expressions are presented to calculate the effective electromagnetic parameters of M-ZnOw composites. To start with, because of the macroscopic isotropic nature of M-ZnOw composites and lossy properties of M-ZnOw itself, an equivalent spherical particle is introduced in the scheme to simplify the unique microscopic structures of M-ZnOw, and the possible limitations of the presented equivalent spherical particle are discussed qualitatively. In addition, different closed-form expressions to calculate the effective electromagnetic parameter are obtained by means of representing the physical situations of conductive network as different correlation functions in the strong fluctuation theory. Finally, the effective permeability of a T-ZnOw/Fe - paraffin composite is calculated by these three expressions in 2-18 GHz frequency range. Very good agreement between the calculated and experimental results on one hand verifies the rationality of presented expressions, and on the other hand indicates that the correlation function plays an important role in improving the performance of the presented expression.

  10. Roles of conducting filament and non-filament regions in the Ta2O5 and HfO2 resistive switching memory for switching reliability.

    Science.gov (United States)

    Park, Tae Hyung; Kim, Hae Jin; Park, Woo Young; Kim, Soo Gil; Choi, Byung Joon; Hwang, Cheol Seong

    2017-05-11

    The endurance of switching cycles, which is a critical measure of device reliability, in an ultra-thin (1.5 nm) Ta2O5 and HfO2 resistive random access (ReRAM) memory cell with a 28 nm lateral dimension was studied using current-voltage (I-V) sweep and closed-loop pulse switching (CLPS) tests. The two devices showed the typical oxygen-deficient conducting-filament (CF)-mediated bipolar resistance switching behaviour, which was induced by the asymmetric electrode configuration: Ta as the oxygen vacancy (VO) source/reservoir and TiN as the inert electrode. In these device geometries, the CF is supposed to initiate at the oxide/TiN interface and to grow towards the Ta electrode during the switch-on process, while the switch-off process was induced by the contraction of the CF from the Ta/oxide interface. Both devices, however, showed inversion (anomalous SET; switching from the off- to on-state) behaviour in the RESET (switching from the on- to off-state) process, which can be explained by the authors' previous model of the hourglass-shaped CF. In this model, once the CF is ruptured, the RESET polarity bias makes the lower portion of the CF regrow to slightly reconnect such a CF through the accelerated migration of VO from the upper-portion CF to the lower-portion CF, which induces switching performance degradation. In the I-V sweeps, the on- and off-states of the devices showed an overall conductance difference approximately corresponding to the integer multiple values of quantum point contact (G0), but there were arbitrary 0.25 and 0.125G0 differences in the conductance values of the on-state for the Ta2O5 and HfO2 devices, respectively. This suggests that these are the minimal units of conductance variation even for a given CF with a standard G0. Although the precise reason for the emergence of such an abnormal conductance unit is not yet understood, its implication for the reliability is critical. Reliable resistive switching was achieved only for the cases where the minimum point conductance was retained even in the off-state; in the other cases, over-SET and over-RESET were induced, which eventually degraded the device reliability. The detailed quantitative analysis of the device failure revealed that the increasing concentration of VO within the non-CF region in the cell decreased the resistance values of that region, which eventually resulted in the over-SET and over-RESET behaviours during the CLPS tests.

  11. Ion/Ioff ratio enhancement and scalability of gate-all-around nanowire negative-capacitance FET with ferroelectric HfO2

    Science.gov (United States)

    Jang, Kyungmin; Saraya, Takuya; Kobayashi, Masaharu; Hiramoto, Toshiro

    2017-10-01

    We have investigated the energy efficiency and scalability of ferroelectric HfO2 (FE:HfO2)-based negative-capacitance field-effect-transistor (NCFET) with gate-all-around (GAA) nanowire (NW) channel structure. Analytic simulation is conducted to characterize NW-NCFET by varying NW diameter and/or thickness of gate insulator as device structural parameters. Due to the negative-capacitance effect and GAA NW channel structure, NW-NCFET is found to have 5× higher Ion/Ioff ratio than classical NW-MOSFET and 2× higher than double-gate (DG) NCFET, which results in wider design window for high Ion/Ioff ratio. To analyze these obtained results from the viewpoint of the device scalability, we have considered constraints regarding very limited device structural spaces to fit by the gate insulator and NW channel for aggresively scaled gate length (Lg) and/or very tight NW pitch. NW-NCFET still has design point with very thinned gate insulator and/or narrowed NW. Therefore, FE:HfO2-based NW-NCFET is applicable to the aggressively scaled technology node of sub-10 nm Lg and to the very tight NW integration of sub-30 nm NW pitch for beyond 7 nm technology. From 2011 to 2014, he engaged in developing high-speed optical transceiver module as an alternative military service in Republic of Korea. His research interest includes the development of steep slope MOSFETs for high energy-efficient operation and ferroelectric HfO2-based semiconductor devices, and fabrication of nanostructured devices. He joined the IBM T.J. Watson Research Center, Yorktown Heights, NY, in 2010, where he worked on advanced CMOS technologies such as FinFET, nanowire FET, SiGe channel and III-V channel. He was also engaged in launching 14 nm SOI FinFET and RMG technology development. Since 2014, he has been an Associate Professor in Institute of Industrial Science, University of Tokyo, Tokyo, Japan, where he has been working on ultralow power transistor and memory technology. Dr. Kobayashi is a member of IEEE and the Japan Society of Applied Physics. Dr. Hiramoto is a fellow of Japan Society of Applied Physics and a member of IEEE and IEICE. He served as the General Chair of Silicon Nanoelectronics Workshop in 2003 and the Program Chair in 1997, 1999, and 2001. He was on Committee of IEDM from 2003 to 2009. He was the Program Chair of Symposium on VLSI Technology in 2013 and was the General Chair in 2015. He is the Program Chair of International Conference on Solid-State Devices and Materials (SSDM) in 2016.

  12. Second-order spherical optoelectronic detector for 3D multi-particles wave emission and propagation in space time domains

    Science.gov (United States)

    Romano, Francesco; Cimmino, Rosario F.

    2017-09-01

    This paper concerns a feasibility study on a 2nd order spherical, or three-dimensional, angular momentum and linear momentum detector for photonic radiation applications. It has been developed in order to obtain a paraxial approximation of physical events observed under Coulomb gauge condition, which is essential to compute both the longitudinal and transverse rotational components of the observed 3-D vortex field, generally neglected by conventional detection systems under current usage. Since light and laser beams are neither full transversal or rotational phenomena, to measure directly and in the same time both the energy, mainly not-rotational, related to the relevant part of the linear momentum and the potential solenoidal energy (vortex), related to the angular momentum, 2nd order spherical, or 3-D, detector techniques are required. In addition, direct 2nd order measure techniques enable development of TEM + DEM [17] studies, therefore allowing for monochromatic complex wave detection with a paraxial accuracy in the relativistic time-space domain. Light and optic or Electromagnetic 2nd order 3-D AnM energy may usefully be used in tre-dimensional optical TEM, noTEM, DEM vortex or laser communications The paper illustrates an innovative quadratic order 3-D spherical model detector applied to directly measure a light source power spectrum and compares the performances of this innovative technique with those obtained with a traditional 1st order system. Results from a number of test experiments conducted in cooperation with INAF Observatories of ArcetriFlorence and Medicina-Bologna (Italy), and focused on telescopic observations of the inter-stellar electromagnetic radiations, are also summarized. The innovative quadratic-order spherical detector turns out to be optimal for optical and/or radio telescopes application, optical and optoelectronic sensors development and gravitational wave 2nd order detectors implementation. Although the proposed method is very

  13. Effects of optical design modifications on thermal performance of a highly reflective HfO2/SiO2/TiO2 three material coating

    Science.gov (United States)

    Ocak, M.; Sert, C.; Okutucu-Özyurt, T.

    2018-02-01

    Effects of layer thickness modifications on laser induced temperature distribution inside three material, highly reflective thin film coatings are studied with numerical simulations. As a base design, a 21 layer coating composed of HfO2, SiO2 and TiO2 layers of quarter wave thickness is considered. First, the laser induced temperature distribution in this base design is obtained. Then the layer thicknesses of the base design are modified and the corresponding temperature distributions in four alternative non-quarter wave coatings are evaluated. The modified thicknesses are determined using an in-house code developed to shift the electric field intensity (EFI) peak from the first high/low layer interface towards the adjacent low index layer that has a higher thermal conductivity, hence, higher laser damage resistance. Meanwhile, the induced increase in the EFI peak is kept at a user defined upper limit. The laser endurance of the base and alternative designs are compared in terms of their estimated temperature distributions. The results indicated that both the peak temperature and the highest interface temperature are decreased by at least 32%, in non-dimensional form, when alternative designs are used instead of the base design. The total reflection of the base design is only decreased from 99.8% to at most 99.4% when alternative designs are used. The study is proved to be successful in improving the laser endurance of three material thin film coatings by lowering the peak and interface temperatures.

  14. Mechanochemical synthesis and electrical conductivity of nanocrystalline delta-Bi2O3 stabilized by HfO2 and ZrO2

    Directory of Open Access Journals (Sweden)

    LJILJANA KARANOVIĆ

    2009-12-01

    Full Text Available A powder mixture of a-Bi2O3 and HfO2, in the molar ratio 2:3, was mechanochemically treated in a planetary ball mill under air, using zirconium oxide vials and balls as the milling medium. After 50 h of milling, the mechanochemical reaction led to the formation of a nanocrystalline a-Bi2O3 phase (fluorite-type solid solution Bi0.87Hf0.59Zr0.63O3.61, with a crystallite size of 20 nm. The mechanochemical reaction started at a very beginning of milling accompanied by an accumulation of ZrO2 arising from the milling tools. The samples prepared after various milling times were characterized by X-ray powder diffraction and DSC analysis. The electrical properties of the as-milled and pressed Bi0.87Hf0.59Zr0.63O3.61powder were studied using impedance spectroscopy in the temperature range from 100 to 700 °C under air. The electrical conductivity was determined to be 9.43×10-6 and 0.080 S cm-1 for the temperatures of 300 and 700 °C, respectively.

  15. Isolation and characterization of apolipoproteins from murine microglia. Identification of a low density lipoprotein-like apolipoprotein J-rich but E-poor spherical particle.

    Science.gov (United States)

    Xu, Q; Li, Y; Cyras, C; Sanan, D A; Cordell, B

    2000-10-13

    Amyloid Abeta deposition is a neuropathologic hallmark of Alzheimer's disease. Activated microglia are intimately associated with plaques and appear to facilitate Abeta deposition, an event believed to contribute to pathogenesis. It is unclear if microglia can modulate pathogenesis of Alzheimer's disease by secreting lipoprotein particles. Here we show that cultured BV2 murine microglial cells, like astrocytes, secrete apolipoprotein E (apoE) and apolipoprotein J (apoJ) in a time-dependent manner. To isolate and identify BV2 microglial particles, gel filtration chromatography was employed to fractionate BV2-conditioned medium. Analyses by Western blot, lipid determination, electron microscopy, and native gel electrophoresis demonstrate that BV2 microglial cells release spherical low density lipoprotein (LDL)-like lipid-containing particles rich in apoJ but poor in apoE. These microglial particles are dissimilar in size, shape, and lipoprotein composition to astrocyte-derived particles. The microglial-derived particles were tested for functional activity. Under conditions of suppressed de novo cholesterol synthesis, the LDL-like particles effectively rescued primary rat cortical neurons from mevastatin-induced neurotoxicity. The particles were also shown to bind Abeta. We speculate that the LDL-like apoJ-rich apoE-poor microglial lipoproteins preferentially bind the lipoprotein receptor, recognizing apoJ, which is abundant in the choroid plexus, facilitating Abeta clearance from the brain. BV2 cells also secrete an apoE-rich lipid-poor species that binds Abeta. Consistent with the role of apoE in Abeta fibril formation and deposition, this microglial species may promote plaque formation.

  16. One step preparation of spherical drug particles by contamination-free dry milling technique with corn starch beads.

    Science.gov (United States)

    Niwa, Toshiyuki; Yoshida, Maria; Hayashi, Naoko; Kondo, Keita

    2017-08-07

    The novel dry milling technique has been developed by using a mechanical powder processor for improving the dissolution properties of poorly water-soluble drugs. It was found that the drug crystals were well pulverized by co-processing with fine particles of corn starch (CS). The morphological observation and particle size evaluation revealed that the processed products formed the composite particles with ordered-mixed structure, having double-layered particles with a core of CS and a coating layer of phenytoin (Phe), as a model drug. This result suggested that the drug crystals were selectively micronized and the resultant miniaturized Phe particles were adhered/fixed on the surface of un-milled CS particles. The mechanical characteristics detected by the indentation test assumed that the brittle Phe crystals sandwiched between elastic CS particles would be successfully crushed down by high shearing stress in the processor. The newly-established dispersion-sedimentation test indicated that the fine Phe particles were immediately detached from the composite particles in aqueous phase, constructing the suspension. The dissolution behavior from the processed particles was found to be improved and strongly dependent on the size and amount of detached Phe particles. Such milling and ordered-mixturization have been also successfully done by using recrystallized larger Phe particles than 100μm. These results would propose the contamination-free dry milling technique without using hard milling balls or beads. The mechanism of the current milling and ordered-mixing phenomena is also provided in this report. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Dependence of the Internal Structure on Water/Particle Volume Ratio in an Amphiphilic Janus Particle-Water-Oil Ternary System: From Micelle-like Clusters to Emulsions of Spherical Droplets.

    Science.gov (United States)

    Noguchi, Tomohiro G; Iwashita, Yasutaka; Kimura, Yasuyuki

    2017-01-31

    Amphiphilic Janus particles (AJP), composed of hydrophilic and hydrophobic hemispheres, are one of the simplest anisotropic colloids, and they exhibit higher surface activities than particles with homogeneous surface properties. Consequently, a ternary system of AJP, water, and oil can form extremely stable Pickering emulsions, with internal structures that depend on the Janus structure of the particles and the system composition. However, the detail of these structures has not been fully explored, especially for the composition range where the amount of the minority liquid phase and AJP are comparable, where one would expect the Janus characteristics to be directly reflected. In this study, we varied the volume ratio of the particles and the minority liquid phase, water, by 2 orders of magnitude around the comparable composition range, and observed the resultant structures at the resolution of the individual particle dimensions by optical microscopy. When the volume ratio of water is smaller than that of the Janus particles, capillary interactions between the hydrophilic hemispheres of the particles induce micelle-like clusters in which the hydrophilic sides of the particles face inward. With increasing water content, these clusters grow into a rodlike morphology. When the water volume exceeds that of the particles, the structure transforms into an emulsion state composed of spherical droplets, colloidosomes, because of the surface activity of particles at the liquid-liquid interface. Thus, we found that a change in volume fraction alters the mechanism of structure formation in the ternary system, and large resulting morphological changes in the self-assembled structures reflect the anisotropy of the particles. The self-assembly shows essential commonalities with that in microemulsions of surfactant molecules, however the AJP system is stabilized only kinetically. Analysis of the dependence of the emulsion droplet size on composition shows that almost all the

  18. Clinical Long-Term Outcome and Reinterventional Rate After Uterine Fibroid Embolization with Nonspherical Versus Spherical Polyvinyl Alcohol Particles

    DEFF Research Database (Denmark)

    Duvnjak, Stevo; Ravn, Pernille; Green, Anders

    2016-01-01

    Purpose: This study was designed to evaluate the long-term clinical outcome and frequency of reinterventions in patients with uterine fibroids treated with embolization at a single center using polyvinyl alcohol microparticles. Methods: The study included all patients with symptomatic uterine...... fibroids treated with uterine fibroid embolization (UFE) with spherical (s-PVA) and nonspherical (ns-PVA) polyvinyl alcohol microparticles during the period January 2001 to January 2011. Clinical success and secondary interventions were examined. Hospital records were reviewed during follow-up, and symptom...

  19. Comparative study of the breakdown transients of thin Al2O3 and HfO2 films in MIM structures and their connection with the thermal properties of materials

    Science.gov (United States)

    Pazos, S.; Aguirre, F.; Miranda, E.; Lombardo, S.; Palumbo, F.

    2017-03-01

    In this work, the breakdown transients of A l 2 O 3 - and HfO2-based metal-insulator-metal (MIM) stacks with the same oxide thickness and identical metal electrodes were compared. Their connection with the thermal properties of the materials was investigated using alternative experimental setups. The differences and similarities between these transients in the fast and progressive breakdown regimes were assessed. According to the obtained results, A l 2 O 3 exhibits longer breakdown transients than HfO2 and requires a higher voltage to initiate a very fast current runaway across the dielectric film. This distinctive behavior is ascribed to the higher thermal conductivity of A l 2 O 3 . Overall results link the breakdown process to the thermal properties of the oxides under test rather than to dissipation effects occurring at the metal electrodes.

  20. Preparation of Controlled-Release Particles Based on Spherical Porous Silica Used as the Drug Carrier by the Dry Coating Method.

    Science.gov (United States)

    Nakamura, Shohei; Kondo, Shihoko; Mohri, Ayaka; Sakamoto, Takatoshi; Yuasa, Hiroshi

    2018-02-12

    A controlled-release formulation is a dosage form that could improve a patient's quality of life by reducing the frequency of administration, while ensuring the continued effect of the medicine and reducing the side effects. To prepare these controlled-release particles, a wet coating method in which a drug is coated with a controlled-release material using water or an organic solvent is used, but with this method, the coating process is very time-consuming and requires large amounts of energy for the drying phase. In addition, contact with water or an organic solvent may cause problems such as alteration of the drug. Therefore, the use of a dry coating method has attracted attention as a means of overcoming these issues. However, since the drug is fixed to the surface of a core particle, it is necessary to further coat it with a water-soluble material. We used spherical porous silica (SPS) particles, considering that the drug fixation via a water-soluble material would not be necessary if the drug were to be placed in the pores of these particles. We used SPS filled with theophylline (TP), a model drug, as the core particles. To prepare controlled-release particles (CRP), a controlled-release layer consisting of hydrogenated castor oil (HCO) was applied to the core particle surface by a dry coating method. The paddle method using 1% w/v polysorbate 80 solution as the test medium was employed to estimate the TP dissolution rate of the resulting CRPs. The 50% dissolution time of TP extended from 14 to 405 min with increasing the amount of the coated HCO. The Korsmeyer-Peppas model applied to the TP dissolution behavior yielded an n value of around 1. Moreover, the K value was comparable with the case in which a zero-order model was applied. It is thought that the dissolution of TP from CRPs will conform to the zero-order model.

  1. Spatial and temporal scales of force and torque acting on wall-mounted spherical particles in open channel flow

    Science.gov (United States)

    Chan-Braun, C.; García-Villalba, M.; Uhlmann, M.

    2013-07-01

    Data from direct numerical simulation of open channel flow over a geometrically rough wall at a bulk Reynolds number of Reb = 2900, generated by Chan-Braun et al. ["Force and torque acting on particles in a transitionally rough open-channel flow," J. Fluid Mech. 684, 441-474 (2011)], 10.1017/jfm.2011.311 are further analysed with respect to the time and length scales of force and torque acting on the wall-mounted spheres. For the two sizes of spheres in a square arrangement (11 and 49 wall units in diameter, yielding hydraulically smooth and transitionally rough flow, respectively), the spatial structure of drag, lift, and spanwise torque is investigated. The auto-correlation and spectra in time as well as the space-time correlation and convection velocities are presented and discussed. It is found that the statistics of spanwise particle torque are similar to those of shear stress at a smooth wall. Particle drag and lift are shown to differ from spanwise particle torque, exhibiting considerably smaller time and length scales; the convection velocities of drag and lift are somewhat larger than those of spanwise torque. Furthermore, correlations between the flow field and particle-related quantities are presented. The spatial structure of the correlation between streamwise velocity and drag/spanwise torque features elongated shapes reminiscent of buffer-layer streaks. The correlation between the pressure field and the particle drag exhibits two opposite-signed bulges on the upstream and downstream sides of a particle.

  2. On device design for steep-slope negative-capacitance field-effect-transistor operating at sub-0.2V supply voltage with ferroelectric HfO2 thin film

    Science.gov (United States)

    Kobayashi, Masaharu; Hiramoto, Toshiro

    2016-02-01

    Internet-of-Things (IoT) technologies require a new energy-efficient transistor which operates at ultralow voltage and ultralow power for sensor node devices employing energy-harvesting techniques as power supply. In this paper, a practical device design guideline for low voltage operation of steep-slope negative-capacitance field-effect-transistors (NCFETs) operating at sub-0.2V supply voltage is investigated regarding operation speed, material requirement and energy efficiency in the case of ferroelectric HfO2 gate insulator, which is the material fully compatible to Complementary Metal-Oxide-Semiconductor (CMOS) process technologies. A physics-based numerical simulator was built to design NCFETs with the use of experimental HfO2 material parameters by modeling the ferroelectric gate insulator and FET channel simultaneously. The simulator revealed that NCFETs with ferroelectric HfO2 gate insulator enable hysteresis-free operation by setting appropriate operation point with a few nm thick gate insulator. It also revealed that, if the finite response time of spontaneous polarization of the ferroelectric gate insulator is 10-100psec, 1-10MHz operation speed can be achieved with negligible hysteresis. Finally, by optimizing material parameters and tuning negative capacitance, 2.5 times higher energy efficiency can be achieved by NCFET than by conventional MOSFETs. Thus, NCFET is expected to be a new CMOS technology platform for ultralow power IoT.

  3. Direct numerical simulation of gas-solid-liquid flows with capillary effects: An application to liquid bridge forces between spherical particles

    Science.gov (United States)

    Sun, Xiaosong; Sakai, Mikio

    2016-12-01

    In this study, a numerical method is developed to perform the direct numerical simulation (DNS) of gas-solid-liquid flows involving capillary effects. The volume-of-fluid method employed to track the free surface and the immersed boundary method is adopted for the fluid-particle coupling in three-phase flows. This numerical method is able to fully resolve the hydrodynamic force and capillary force as well as the particle motions arising from complicated gas-solid-liquid interactions. We present its application to liquid bridges among spherical particles in this paper. By using the DNS method, we obtain the static bridge force as a function of the liquid volume, contact angle, and separation distance. The results from the DNS are compared with theoretical equations and other solutions to examine its validity and suitability for modeling capillary bridges. Particularly, the nontrivial liquid bridges formed in triangular and tetrahedral particle clusters are calculated and some preliminary results are reported. We also perform dynamic simulations of liquid bridge ruptures subject to axial stretching and particle motions driven by liquid bridge action, for which accurate predictions are obtained with respect to the critical rupture distance and the equilibrium particle position, respectively. As shown through the simulations, the strength of the present method is the ability to predict the liquid bridge problem under general conditions, from which models of liquid bridge actions may be constructed without limitations. Therefore, it is believed that this DNS method can be a useful tool to improve the understanding and modeling of liquid bridges formed in complex gas-solid-liquid flows.

  4. Void initiation from interfacial debonding of spherical silicon particles inside a silicon-copper nanocomposite: a molecular dynamics study

    Science.gov (United States)

    Cui, Yi; Chen, Zengtao

    2017-02-01

    Silicon particles with diameters from 1.9 nm to 30 nm are embedded in a face-centered-cubic copper matrix to form nanocomposite specimens for simulation. The interfacial debonding of silicon particles from the copper matrix and the subsequent growth of nucleated voids are studied via molecular dynamics (MD). The MD results are examined from several different perspectives. The overall mechanical performance is monitored by the average stress-strain response and the accumulated porosity. The ‘relatively farthest-traveled’ atoms are identified to characterize the onset of interfacial debonding. The relative displacement field is plotted to illustrate both subsequent interfacial debonding and the growth of a nucleated void facilitated by a dislocation network. Our results indicate that the initiation of interfacial debonding is due to the accumulated surface stress if the matrix is initially dislocation-free. However, pre-existing dislocations can make a considerable difference. In either case, the dislocation emission also contributes to the subsequent debonding process. As for the size effect, the debonding of relatively larger particles causes a drop in the stress-strain curve. The volume fraction of second-phase particles is found to be more influential than the size of the simulation box on the onset of interfacial debonding. The volume fraction of second-phase particles also affects the shape of the nucleated void and, therefore, influences the stress response of the composite.

  5. The influence of surface preparation on low temperature HfO2 ALD on InGaAs (001) and (110) surfaces

    Science.gov (United States)

    Kent, Tyler; Tang, Kechao; Chobpattana, Varistha; Negara, Muhammad Adi; Edmonds, Mary; Mitchell, William; Sahu, Bhagawan; Galatage, Rohit; Droopad, Ravi; McIntyre, Paul; Kummel, Andrew C.

    2015-10-01

    Current logic devices rely on 3D architectures, such as the tri-gate field effect transistor (finFET), which utilize the (001) and (110) crystal faces simultaneously thus requiring passivation methods for the (110) face in order to ensure a pristine 3D surface prior to further processing. Scanning tunneling microscopy (STM), x-ray photoelectron spectroscopy (XPS), and correlated electrical measurement on MOSCAPs were utilized to compare the effects of a previously developed in situ pre-atomic layer deposition (ALD) surface clean on the InGaAs (001) and (110) surfaces. Ex situ wet cleans are very effective on the (001) surface but not the (110) surface. Capacitance voltage indicated the (001) surface with no buffered oxide etch had a higher Cmax hypothesized to be a result of poor nucleation of HfO2 on the native oxide. An in situ pre-ALD surface clean employing both atomic H and trimethylaluminum (TMA) pre-pulsing, developed by Chobpattana et al. and Carter et al. for the (001) surface, was demonstrated to be effective on the (110) surface for producing low Dit high Cox MOSCAPs. Including TMA in the pre-ALD surface clean resulted in reduction of the magnitude of the interface state capacitance. The XPS studies show the role of atomic H pre-pulsing is to remove both carbon and oxygen while STM shows the role of TMA pre-pulsing is to eliminate H induced etching. Devices fabricated at 120 °C and 300 °C were compared.

  6. Understanding the discrete element method simulation of non-spherical particles for granular and multi-body systems

    CERN Document Server

    Matuttis, Hans-Georg

    2014-01-01

    Gives readers a more thorough understanding of DEM and equips researchers for independent work and an ability to judge methods related to simulation of polygonal particles Introduces DEM from the fundamental concepts (theoretical mechanics and solidstate physics), with 2D and 3D simulation methods for polygonal particlesProvides the fundamentals of coding discrete element method (DEM) requiring little advance knowledge of granular matter or numerical simulationHighlights the numerical tricks and pitfalls that are usually only realized after years of experience, with relevant simple experiment

  7. Spherical models

    CERN Document Server

    Wenninger, Magnus J

    2012-01-01

    Well-illustrated, practical approach to creating star-faced spherical forms that can serve as basic structures for geodesic domes. Complete instructions for making models from circular bands of paper with just a ruler and compass. Discusses tessellation, or tiling, and how to make spherical models of the semiregular solids and concludes with a discussion of the relationship of polyhedra to geodesic domes and directions for building models of domes. "". . . very pleasant reading."" - Science. 1979 edition.

  8. A numerical model for aggregations formation and magnetic driving of spherical particles based on OpenFOAM®.

    Science.gov (United States)

    Karvelas, E G; Lampropoulos, N K; Sarris, I E

    2017-04-01

    This work presents a numerical model for the formation of particle aggregations under the influence of a permanent constant magnetic field and their driving process under a gradient magnetic field, suitably created by a Magnetic Resonance Imaging (MRI) device. The model is developed in the OpenFOAM platform and it is successfully compared to the existing experimental and numerical results in terms of aggregates size and their motion in water solutions. Furthermore, several series of simulations are performed for two common types of particles of different diameter in order to verify their aggregation and flow behaviour, under various constant and gradient magnetic fields in the usual MRI working range. Moreover, the numerical model is used to measure the mean length of aggregations, the total time needed to form and their mean velocity under different permanent and gradient magnetic fields. The present model is found to predict successfully the size, velocity and distribution of aggregates. In addition, our simulations showed that the mean length of aggregations is proportional to the permanent magnetic field magnitude and particle diameter according to the relation : l¯a=7.5B0di3/2. The mean velocity of the aggregations is proportional to the magnetic gradient, according to : u¯a=6.63G˜B0 and seems to reach a steady condition after a certain period of time. The mean time needed for particles to aggregate is proportional to permanent magnetic field magnitude, scaled by the relationship : t¯a∝7B0. A numerical model to predict the motion of magnetic particles for medical application is developed. This model is found suitable to predict the formation of aggregations and their motion under the influence of permanent and gradient magnetic fields, respectively, that are produced by an MRI device. The magnitude of the external constant magnetic field is the most important parameter for the aggregations formation and their driving. Copyright © 2017 Elsevier B.V. All

  9. Propagation of a spherical shock wave in mixture of non-ideal gas and small solid particles under gravitational field with conductive and radiative heat fluxes

    Science.gov (United States)

    Nath, Gorakh

    Self-similar solutions are obtained for one-dimensional unsteady adiabatic flow behind a spherical shock wave propagating in a dusty gas with conductive and radiative heat fluxes under a gravitational field. The shock is assumed to be driven out by a moving piston and the dusty gas to be a mixture of non-ideal (or perfect) gas and small solid particles, in which solid particles are continuously distributed. It is assumed that the equilibrium flow-conditions are maintained and variable energy input is continuously supplied by the piston. The heat conduction is express in terms of Fourier’s law and the radiation is considered to be of the diffusion type for an optically thick grey gas model. The thermal conductivity and the absorption coefficient are assumed to vary with temperature and density. The medium is assumed to be under a gravitational field due to heavy nucleus at the origin (Roche Model). The unsteady model of Roche consists of a dusty gas distributed with spherical symmetry around a nucleus having large mass It is assumed that the gravitational effect of the mixture itself can be neglected compared with the attraction of the heavy nucleus. The density of the ambient medium is taken to be constant. Our analysis reveals that after inclusion of gravitational field effect surprisingly the shock strength increases and remarkable difference can be found in the distribution of flow variables. The effects of the variation of the heat transfer parameters, the gravitational parameter and non-idealness of the gas in the mixture are investigated. Also, the effects of an increase in (i) the mass concentration of solid particles in the mixture and (ii) the ratio of the density of solid particles to the initial density of the gas on the flow variables are investigated. It is found that the shock strength is increased with an increase in the value of gravitational parameter. Further, it is investigated that the presence of gravitational field increases the

  10. Spatial and temporal scales of force and torque acting on wall-mounted spherical particles in open channel flow

    OpenAIRE

    Chan-Braun, Clemens; Garcia-Villalba, Manuel; Uhlmann, Markus

    2013-01-01

    Data from direct numerical simulation of open channel flow over a geometrically rough wall at a bulk Reynolds number of 2900, generated by Chan-Braun et al. ["Force and torque acting on particles in a transitionally rough open-channel flow", J. Fluid Mech. 684, 441--474 (2011), 10.1017/jfm.2011.311] are further analysed with respect to the time and length scales of force and torque acting on the wall-mounted spheres. For the two sizes of spheres in a square arrangement (11 and 49 wall units i...

  11. Comparison of tarnish level in two types of high- copper dental amalgams with lathe-cut and spherical particles produced in Iran

    Directory of Open Access Journals (Sweden)

    Mosavi-nasab SM.

    2001-09-01

    Full Text Available "nAbstract: There are two types of high-copper dental amalgams produced in Iran; Cinalloy (lathe-cut particles and Cinalux (spherical particles. Tarnish is one of the disadvantages of dental amalgam, which precedes corrosion, and in fact it means real destruction of restorative materials. The purpose of this study was to compare the extent of tarnish in Cinalux and Cinalloy amalgams. 32 patients, with at least two carious or poorly restored teeth were selected. Then, each tooth was restored with one of these two types of dental amalgams. The restorations were polished after 24 hours and patients were followed up after 9 months. The restorations were categorized in four groups of no change, one plus (1-30%, two plus (30-60% and three plus (more than 60% according to the level of discoloration. The results showed that the level of tarnish in Cinalux group was significantly less than Cinalloy group. The mean of tarnish for Cinalloy and Cinalux was 2.09±0.59 and 1.72±0.68 respectively. In addition, statistical analysis showed that there was no significant relationship between tarnish and Oral hygiene, smoking, operator or type and place of restoration.

  12. HfO2 high-k solid-state incandescent devices: performance improvement using a Ti-embedded layer and observation of conductive paths as light-emitting sources.

    Science.gov (United States)

    Liu, Yiwei; Yang, Can; Zhao, Jinyan; Wu, Shengli; Dai, Liyan; Niu, Gang

    2017-08-18

    Solid-state incandescent light-emission devices (SSI-LEDs) with a metal-oxide-semiconductor structure are promising candidates for future broadband light-emission devices. In this work, the electrical and light-emission features of SSI-LEDs based on HfO2 high-k thin films with or without the Ti-embedded layer on p-type silicon wafers have been studied. It turns out that the Ti-embedded layer can effectively reduce the turn-on voltage, thus improving the fluorescence efficiency of SSI-LEDs. The combination of scanning electron microscopy, atomic force microscope (AFM) and conductive AFM results unambiguously clarifies that conductive filaments, which are formed due to local thermal excitation during the forming process, are accompanied by the formation of pits on the HfO2 surface and are responsible for the light emission. This work develops an effective approach to improving the luminescence performance of SSI-LEDs and experimentally explains the light-emitting mechanism of such devices, which is of great importance to eventually realizng broadband light-emitting devices with low power consumption.

  13. Spherical Camera

    Science.gov (United States)

    1997-01-01

    Developed largely through a Small Business Innovation Research contract through Langley Research Center, Interactive Picture Corporation's IPIX technology provides spherical photography, a panoramic 360-degrees. NASA found the technology appropriate for use in guiding space robots, in the space shuttle and space station programs, as well as research in cryogenic wind tunnels and for remote docking of spacecraft. Images of any location are captured in their entirety in a 360-degree immersive digital representation. The viewer can navigate to any desired direction within the image. Several car manufacturers already use IPIX to give viewers a look at their latest line-up of automobiles. Another application is for non-invasive surgeries. By using OmniScope, surgeons can look more closely at various parts of an organ with medical viewing instruments now in use. Potential applications of IPIX technology include viewing of homes for sale, hotel accommodations, museum sites, news events, and sports stadiums.

  14. Development and Performance Evaluations of HfO2-Si and Rare Earth-Si Based Environmental Barrier Bond Coat Systems for SiC/SiC Ceramic Matrix Composites

    Science.gov (United States)

    Zhu, Dongming

    2014-01-01

    Ceramic environmental barrier coatings (EBC) and SiCSiC ceramic matrix composites (CMCs) will play a crucial role in future aircraft propulsion systems because of their ability to significantly increase engine operating temperatures, improve component durability, reduce engine weight and cooling requirements. Advanced EBC systems for SiCSiC CMC turbine and combustor hot section components are currently being developed to meet future turbine engine emission and performance goals. One of the significant material development challenges for the high temperature CMC components is to develop prime-reliant, high strength and high temperature capable environmental barrier coating bond coat systems, since the current silicon bond coat cannot meet the advanced EBC-CMC temperature and stability requirements. In this paper, advanced NASA HfO2-Si based EBC bond coat systems for SiCSiC CMC combustor and turbine airfoil applications are investigated. The coating design approach and stability requirements are specifically emphasized, with the development and implementation focusing on Plasma Sprayed (PS) and Electron Beam-Physic Vapor Deposited (EB-PVD) coating systems and the composition optimizations. High temperature properties of the HfO2-Si based bond coat systems, including the strength, fracture toughness, creep resistance, and oxidation resistance were evaluated in the temperature range of 1200 to 1500 C. Thermal gradient heat flux low cycle fatigue and furnace cyclic oxidation durability tests were also performed at temperatures up to 1500 C. The coating strength improvements, degradation and failure modes of the environmental barrier coating bond coat systems on SiCSiC CMCs tested in simulated stress-environment interactions are briefly discussed and supported by modeling. The performance enhancements of the HfO2-Si bond coat systems with rare earth element dopants and rare earth-silicon based bond coats are also highlighted. The advanced bond coat systems, when integrated with advanced EBC top coats, showed promise to achieve 1500 C temperature capability, helping enable next generation turbine engines with significantly improved engine component temperature capability and long-term durability.

  15. A direct route for the synthesis of nanometer-sized Bi2WO6 particles loaded on a spherical MCM-48 mesoporous molecular sieve.

    Science.gov (United States)

    Jiang, Lin; Wang, Lingzhi; Zhang, Jinlong

    2010-11-14

    Bi(2)WO(6) nanoparticles loaded on a spherical MCM-48 mesoporous molecular sieve with a high photocatalytic activity in the visible-light range was synthesized for the first time using a facile one-step process.

  16. Ion induced crystallization and grain growth of hafnium oxide nano-particles in thin-films deposited by radio frequency magnetron sputtering

    Science.gov (United States)

    Dhanunjaya, M.; Khan, S. A.; Pathak, A. P.; Avasthi, D. K.; Nageswara Rao, S. V. S.

    2017-12-01

    We report on the swift heavy ion (SHI) irradiation induced crystallization and grain growth of HfO2 nanoparticles (NPs) within the HfO2 thin-films deposited by radio frequency (RF) magnetron sputtering technique. As grown films consisted of amorphous clusters of non-spherical HfO2 NPs. These amorphous clusters are transformed to crystalline grains under 100 MeV Ag ion irradiation. These crystallites are found to be spherical in shape and are well dispersed within the films. The average size of these crystallites is found to increase with fluence. Pristine and irradiated films have been characterized by high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), grazing incident x-ray diffraction (GIXRD) and photo luminescence (PL) measurements. The PL measurements suggested the existence of different types of oxygen related defects in pristine and irradiated samples. The observed results on crystallization and grain growth under the influence of SHI are explained within the framework of thermal spike model. The results are expected to provide useful information for understanding the electronic excitation induced crystallization of nanoparticles and can lead to useful applications in electronic and photonic devices.

  17. Development and Property Evaluation of Selected HfO2-Silicon and Rare Earth-Silicon Based Bond Coats and Environmental Barrier Coating Systems for SiC/SiC Ceramic Matrix Composites

    Science.gov (United States)

    Zhu, Dongming

    2016-01-01

    Ceramic environmental barrier coatings (EBC) and SiC/SiC ceramic matrix composites (CMCs) will play a crucial role in future aircraft propulsion systems because of their ability to significantly increase engine operating temperatures, improve component durability, reduce engine weight and cooling requirements. Advanced EBC systems for SiC/SiC CMC turbine and combustor hot section components are currently being developed to meet future turbine engine emission and performance goals. One of the significant material development challenges for the high temperature CMC components is to develop prime-reliant, high strength and high temperature capable environmental barrier coating bond coat systems, since the current silicon bond coat cannot meet the advanced EBC-CMC temperature and stability requirements. In this paper, advanced NASA HfO2-Si and rare earth Si based EBC bond coat EBC systems for SiC/SiC CMC combustor and turbine airfoil applications are investigated. High temperature properties of the advanced EBC systems, including the strength, fracture toughness, creep and oxidation resistance have been studied and summarized. The advanced NASA EBC systems showed some promise to achieve 1500C temperature capability, helping enable next generation turbine engines with significantly improved engine component temperature capability and durability.

  18. O-vacancies in (i) nano-crystalline HfO2 and (i) non-crystalline SiO2 and Si3N4 studied by X-ray absorption spectroscopy.

    Science.gov (United States)

    Lucovsky, Gerald; Miotti, Leonardo; Bastos, Karen Paz

    2012-06-01

    Performance and reliability in semiconductor devices are limited by electronically active defects, primarily O-atom and N-atom vacancies. Synchrotron X-ray spectroscopy results, interpreted in the context of two-electron multiplet theories, have been used to analyze conduction band edge, and O-vacancy defect states in nano-crystalline transition metal oxides, e.g., HfO2, and the noncrystalline dielectrics, SiO2, Si3N4 and Si-oxynitride alloys. Two-electron multiplet theory been used to develop a high-spin state equivalent d2 model for O-vacancy allowed transitions and negative ion states as detected by X-ray absorption spectroscopy in the O K pre-edge regime. Comparisons between theory and experiment have used Tanabe-Sugano energy level diagrams for determining the symmetries and relative energies of intra-d-state transitions for an equivalent d2 ground state occupancy. Trap-assisted-tunneling, Poole-Frenkel hopping transport, and the negative bias temperature instability have been explained in terms of injection and/or trapping into O-atom and N-atom vacancy sites, and applied to gate dielectric, and metal-insulator-metal structures.

  19. Environmental Stability and Oxidation Behavior of HfO2-Si and YbGd(O) Based Environmental Barrier Coating Systems for SiCSiC Ceramic Matrix Composites

    Science.gov (United States)

    Zhu, Dongming; Farmer, Serene; McCue, Terry R.; Harder, Bryan; Hurst, Janet B.

    2017-01-01

    Ceramic environmental barrier coatings (EBC) and SiCSiC ceramic matrix composites (CMCs) will play a crucial role in future aircraft propulsion systems because of their ability to significantly increase engine operating temperatures, improve component durability, reduce engine weight and cooling requirements. Advanced EBC systems for SiCSiC CMC turbine and combustor hot section components are currently being developed to meet future turbine engine emission and performance goals. One of the significant material development challenges for the high temperature CMC components is to develop prime-reliant, environmental durable environmental barrier coating systems. In this paper, the durability and performance of advanced Electron Beam-Physical Vapor Deposition (EB-PVD) NASA HfO2-Si and YbGdSi(O) EBC bond coat top coat systems for SiCSiC CMC have been summarized. The high temperature thermomechanical creep, fatigue and oxidation resistance have been investigated in the laboratory simulated high-heat-flux environmental test conditions. The advanced NASA EBC systems showed promise to achieve 1500C temperature capability, helping enable next generation turbine engines with significantly improved engine component temperature capability and durability.

  20. Inversion of band patterns in spherical tumblers.

    Science.gov (United States)

    Chen, Pengfei; Lochman, Bryan J; Ottino, Julio M; Lueptow, Richard M

    2009-04-10

    Bidisperse granular mixtures in spherical tumblers segregate into three bands: one at each pole and one at the equator. For low fill levels, large particles are at the equator; for high fill levels, the opposite occurs. Segregation is robust, though the transition depends on fill level, particle size, and rotational speed. Discrete element method simulations reproduce surface patterns and reveal internal structures. Particle trajectories show that small particles flow farther toward the poles than large particles in the upstream portion of the flowing layer for low fill levels leading to a band of small particles at each pole. The opposite occurs for high fill levels, though more slowly.

  1. Partitioning behavior and stabilization of hydrophobically coated HfO2, ZrO2 and Hfx Zr 1-x O2 nanoparticles with natural organic matter reveal differences dependent on crystal structure.

    Science.gov (United States)

    Navarro, Divina A; Depner, Sean W; Watson, David F; Aga, Diana S; Banerjee, Sarbajit

    2011-11-30

    The interactions of engineered nanomaterials with natural organic matter (NOM) exert a profound influence on the mobilities of the former in the environment. However, the influence of specific nanomaterial structural characteristics on the partitioning and colloidal stabilization of engineered nanomaterials in various ecological compartments remains underexplored. Herein, we present a systematic study of the interactions of humic acid (HA, as a model for NOM) with monodisperse, well-characterized, ligand-passivated HfO(2), ZrO(2), and solid-solution Hf(x)Zr(1-x)O(2) nanoparticles (NPs). We note that mixing with HA induces the almost complete phase transfer of hydrophobically coated monoclinic metal oxide (MO) NPs from hexane to water. Furthermore, HA is seen to impart appreciable colloidal stabilization to the NPs in the aqueous phase. In contrast, phase transfer and aqueous-phase colloidal stabilization has not been observed for tetragonal MO-NPs. A mechanistic model for the phase transfer and aqueous dispersal of MO-NPs is proposed on the basis of evidence from transmission electron microscopy, ζ-potential measurements, dynamic light scattering, Raman and infrared spectroscopies, elemental analysis, and systematic experiments on a closely related set of MO-NPs with varying composition and crystal structure. The data indicate the synergistic role of over-coating (micellar), ligand substitution (coordinative), and electrostatic processes wherein HA acts both as an amphiphilic molecule and a charged chelating ligand. The strong observed preference for the phase transfer of monoclinic instead of tetragonal NPs indicates the importance of the preferential binding of HA to specific crystallographic facets and suggests the possibility of being able to design NPs to minimize their mobilities in the aquatic environment. Copyright © 2011 Elsevier B.V. All rights reserved.

  2. Spherical particles of halophilic archaea correlate with exposure to low water activity--implications for microbial survival in fluid inclusions of ancient halite.

    Science.gov (United States)

    Fendrihan, S; Dornmayr-Pfaffenhuemer, M; Gerbl, F W; Holzinger, A; Grösbacher, M; Briza, P; Erler, A; Gruber, C; Plätzer, K; Stan-Lotter, H

    2012-09-01

    Viable extremely halophilic archaea (haloarchaea) have been isolated from million-year-old salt deposits around the world; however, an explanation of their supposed longevity remains a fundamental challenge. Recently small roundish particles in fluid inclusions of 22 000- to 34 000-year-old halite were identified as haloarchaea capable of proliferation (Schubert BA, Lowenstein TK, Timofeeff MN, Parker MA, 2010, Environmental Microbiology, 12, 440-454). Searching for a method to produce such particles in the laboratory, we exposed rod-shaped cells of Halobacterium species to reduced external water activity (a(w)). Gradual formation of spheres of about 0.4 μm diameter occurred in 4 M NaCl buffer of a(w) ≤ 0.75, but exposure to buffered 4 M LiCl (a(w) ≤ 0.73) split cells into spheres within seconds, with concomitant release of several proteins. From one rod, three or four spheres emerged, which re-grew to normal rods in nutrient media. Biochemical properties of rods and spheres were similar, except for a markedly reduced ATP content (about 50-fold) and an increased lag phase of spheres, as is known from dormant bacteria. The presence of viable particles of similar sizes in ancient fluid inclusions suggested that spheres might represent dormant states of haloarchaea. The easy production of spheres by lowering a(w) should facilitate their investigation and could help to understand the mechanisms for microbial survival over geological times. © 2012 Blackwell Publishing Ltd.

  3. Optical properties of spherical gold mesoparticles

    DEFF Research Database (Denmark)

    Evlyukhin, A. B.; Kuznetsov, A. I.; Novikov, S. M.

    2012-01-01

    Optical properties of spherical gold particles with diameters of 150-650 nm (mesoparticles) are studied by reflectance spectroscopy. Particles are fabricated by laser-induced transfer of metallic droplets onto metal and dielectric substrates. Contributions of higher multipoles (beyond the quadrup......Optical properties of spherical gold particles with diameters of 150-650 nm (mesoparticles) are studied by reflectance spectroscopy. Particles are fabricated by laser-induced transfer of metallic droplets onto metal and dielectric substrates. Contributions of higher multipoles (beyond...... results obtained in homogeneous environment is demonstrated. Multipole resonance features in the experimental reflection spectra of particles located on a gold substrate, in the wavelength range of 500-1000 nm, are discussed and theoretically analyzed on the basis of finite-difference time...

  4. Transient Enhancement ('Spike-on-Tail') Observed on Neutral-Beam-Injected Energetic Ion Spectra Using the E||B Neutral Particle Analyzer in the National Spherical Torus Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Medley, S. S. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Gorelenkov, N. N. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Bell, R. E. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Fredrickson, E. D. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Gerhardt, S. P. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); LeBlanc, B. P. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Podesta, M. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Roquemore, A. L. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)

    2010-06-01

    An increase of up to four-fold in the E||B Neutral Particle Analyzer (NPA) charge exchange neutral flux localized at the Neutral Beam (NB) injection full energy is observed in the National Spherical Torus Experiment (NSTX). Termed the High-Energy Feature (HEF), it appears on the NB-injected energetic ion spectrum only in discharges where tearing or kink-type modes (f < 10 kHz) are absent, TAE activity (f ~ 10-150 kHz) is weak (δBrms < 75 mGauss) and CAE/GAE activity (f ~ 400 – 1200 kHz) is robust. The feature exhibits a growth time of ~ 20 - 80 ms and occasionally develops a slowing down distribution that continues to evolve over periods of 100's of milliseconds, a time scale long compared with the typical ~ 10's ms equilibration time of the NB injected particles. The HEF is observed only in H-mode (not L-mode) discharges with injected NB power of 4 MW or greater and in the field pitch range v||/v ~ 0.7 – 0.9; i.e. only for passing (never trapped) energetic ions. The HEF is suppressed by vessel conditioning using lithium deposition at rates ~ 100 mg/shot, a level sufficient to suppress ELM activity. Increases of ~ 10 - 30 % in the measured neutron yield and total stored energy are observed to coincide with the feature along with broadening of measured Te(r), Ti(r) and ne(r) profiles. However, TRANSP analysis shows that such increases are driven by plasma profile changes and not the HEF phenomenon itself. Though a definitive mechanism has yet to be developed, the HEF appears to be caused by a form of TAE/CAE wave-particle interaction that distorts of the NB fast ion distribution in phase space.

  5. Spherical tube hypersurfaces

    CERN Document Server

    Isaev, Alexander

    2011-01-01

    We examine Levi non-degenerate tube hypersurfaces in complex linear space which are "spherical," that is, locally CR-equivalent to the real hyperquadric. Spherical hypersurfaces are characterized by the condition of the vanishing of the CR-curvature form, so such hypersurfaces are flat from the CR-geometric viewpoint. On the other hand, such hypersurfaces are also of interest from the point of view of affine geometry. Thus our treatment of spherical tube hypersurfaces in this book is two-fold: CR-geometric and affine-geometric. As the book shows, spherical tube hypersurfaces possess remarkable properties. For example, every such hypersurface is real-analytic and extends to a closed real-analytic spherical tube hypersurface in complex space. One of our main goals is to provide an explicit affine classification of closed spherical tube hypersurfaces whenever possible. In this book we offer a comprehensive exposition of the theory of spherical tube hypersurfaces, starting with the idea proposed in the pioneering...

  6. Space Radiation Detector with Spherical Geometry

    Science.gov (United States)

    Wrbanek, John D. (Inventor); Fralick, Gustave C. (Inventor); Wrbanek, Susan Y. (Inventor)

    2012-01-01

    A particle detector is provided, the particle detector including a spherical Cherenkov detector, and at least one pair of detector stacks. In an embodiment of the invention, the Cherenkov detector includes a sphere of ultraviolet transparent material, coated by an ultraviolet reflecting material that has at least one open port. The Cherenkov detector further includes at least one photodetector configured to detect ultraviolet light emitted from a particle within the sphere. In an embodiment of the invention, each detector stack includes one or more detectors configured to detect a particle traversing the sphere.

  7. Crystal growth of drug materials by spherical crystallization

    Science.gov (United States)

    Szabó-Révész, P.; Hasznos-Nezdei, M.; Farkas, B.; Göcző, H.; Pintye-Hódi, K.; Erős, I.

    2002-04-01

    One of the crystal growth processes is the production of crystal agglomerates by spherical crystallization. Agglomerates of drug materials were developed by means of non-typical (magnesium aspartate) and typical (acetylsalicylic acid) spherical crystallization techniques. The growth of particle size and the spherical form of the agglomerates resulted in formation of products with good bulk density, flow, compactibility and cohesivity properties. The crystal agglomerates were developed for direct capsule-filling and tablet-making.

  8. Propagation of a spherical shock wave in mixture of non-ideal gas and small solid particles under the influence of gravitational field with conductive and radiative heat fluxes

    Science.gov (United States)

    Nath, G.

    2016-01-01

    Self-similar solutions are obtained for one-dimensional unsteady adiabatic flow behind a spherical shock wave propagating in a dusty gas with conductive and radiative heat fluxes under the influence of a gravitational field. The shock is assumed to be driven out by a moving piston and the dusty gas to be a mixture of non-ideal gas and small solid particles, in which solid particles are uniformly distributed. It is assumed that the equilibrium flow-conditions are maintained and variable energy input is continuously supplied by the piston. The heat conduction is expressed in terms of Fourier's law and the radiation is considered to be of the diffusion type for an optically thick grey gas model. The thermal conductivity K and the absorption coefficient αR are assumed to vary with temperature and density. The medium is assumed to be under the influence of a gravitational field due to central mass ( bar{m} ) at the origin (Roche Model). It is assumed that the gravitational effect of the mixture itself can be neglected compared with the attraction of the central mass. The initial density of the ambient medium is taken to be always constant. The effects of the variation of the gravitational parameter and nonidealness of the gas in the mixture are investigated. Also, the effects of an increase in (i) the mass concentration of solid particles in the mixture and (ii) the ratio of the density of solid particles to the initial density of the gas on the flow variables are investigated. It is shown that due to an increase in the gravitational parameter the compressibility of the medium at any point in the flow-field behind the shock decreases and all other flow variables and the shock strength are increased. Further, it is found that the presence of gravitational field increases the compressibility of the medium, due to which it is compressed and therefore the distance between the piston and the shock surface is reduced. The shock waves in dusty gas under the influence of a

  9. Einstein-Vlasov system in spherical symmetry. II. Spherical perturbations of static solutions

    Science.gov (United States)

    Gundlach, Carsten

    2017-10-01

    We reduce the equations governing the spherically symmetric perturbations of static spherically symmetric solutions of the Einstein-Vlasov system (with either massive or massless particles) to a single stratified wave equation -ψ,t t=H ψ , with H containing second derivatives in radius, and integrals over energy and angular momentum. We identify an inner product with respect to which H is symmetric, and use the Ritz method to approximate the lowest eigenvalues of H numerically. For two representative background solutions with massless particles we find a single unstable mode with a growth rate consistent with the universal one found by Akbarian and Choptuik in nonlinear numerical time evolutions.

  10. A thermodynamic model for the solubility of HfO2(am) in the aqueous K +– HCO3-– CO32-–O-–H2O system

    Energy Technology Data Exchange (ETDEWEB)

    Rai, Dhanpat; Kitamura, Akira; Rosso, Kevin M.

    2017-01-01

    Solubility of HfO2(am) was determined as a function of KHCO3 concentrations ranging from 0.001 mol·kg-1 to 0.1 mol·kg-1. The solubility of HfO2(am) increased dramatically with the increase in KHCO3 concentrations, indicating that Hf(IV) makes strong complexes with carbonate. Thermodynamic equilibrium constants for the formation of Hf-carbonate complexes were determined using both the Pitzer and SIT models. The dramatic increase in Hf concentrations with the increase in KHCO3 concentrations can best be described by the formation of Hf(OH-)2(CO3)22- and Hf(CO3)56-. The log10 K0 values for the reactions [Hf4++2CO32-+2OH-⇌Hf(OH)2(CO3)22-] and [Hf4++5CO32-⇌Hf(CO3)56-], based on the SIT model, were determined to be 44.53±0.46 and 41.53±0.46, respectively, and based on the Pitzer model they were 44.56±0.48 and 40.20±0.48, respectively.

  11. Spherical aberration from trajectories in real and hard-edge ...

    Indian Academy of Sciences (India)

    (3)–(4) by comparing with spherical aberration obtained from the ensemble of particle trajectories. The scaled field gives the same focal length. 3. Particle trajectory. 3.1 Ray equation with aberration. The particle trajectory in a solenoid magnet with aberrations is governed by the third-order paraxial ray equation given in eq.

  12. Overview of spherical tokamak research in Japan

    Science.gov (United States)

    Takase, Y.; Ejiri, A.; Fujita, T.; Fukumoto, N.; Fukuyama, A.; Hanada, K.; Idei, H.; Nagata, M.; Ono, Y.; Tanaka, H.; Uchida, M.; Horiuchi, R.; Kamada, Y.; Kasahara, H.; Masuzaki, S.; Nagayama, Y.; Oishi, T.; Saito, K.; Takeiri, Y.; Tsuji-Iio, S.

    2017-10-01

    Nationally coordinated research on spherical tokamak is being conducted in Japan. Recent achievements include: (i) plasma current start-up and ramp-up without the use of the central solenoid by RF waves (in electron cyclotron and lower hybrid frequency ranges), (ii) plasma current start-up by AC Ohmic operation and by coaxial helicity injection, (iii) development of an advanced fuelling technique by compact toroid injection, (iv) ultra-long-pulse operation and particle control using a high temperature metal wall, (v) access to the ultra-high-β regime by high-power reconnection heating, and (vi) improvement of spherical tokamak plasma stability by externally applied helical field.

  13. Spherically Actuated Motor

    Science.gov (United States)

    Peeples, Steven

    2015-01-01

    A three degree of freedom (DOF) spherical actuator is proposed that will replace functions requiring three single DOF actuators in robotic manipulators providing space and weight savings while reducing the overall failure rate. Exploration satellites, Space Station payload manipulators, and rovers requiring pan, tilt, and rotate movements need an actuator for each function. Not only does each actuator introduce additional failure modes and require bulky mechanical gimbals, each contains many moving parts, decreasing mean time to failure. A conventional robotic manipulator is shown in figure 1. Spherical motors perform all three actuation functions, i.e., three DOF, with only one moving part. Given a standard three actuator system whose actuators have a given failure rate compared to a spherical motor with an equal failure rate, the three actuator system is three times as likely to fail over the latter. The Jet Propulsion Laboratory reliability studies of NASA robotic spacecraft have shown that mechanical hardware/mechanism failures are more frequent and more likely to significantly affect mission success than are electronic failures. Unfortunately, previously designed spherical motors have been unable to provide the performance needed by space missions. This inadequacy is also why they are unavailable commercially. An improved patentable spherically actuated motor (SAM) is proposed to provide the performance and versatility required by NASA missions.

  14. Spherical geodesic mesh generation

    Energy Technology Data Exchange (ETDEWEB)

    Fung, Jimmy [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Kenamond, Mark Andrew [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Burton, Donald E. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Shashkov, Mikhail Jurievich [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-02-27

    In ALE simulations with moving meshes, mesh topology has a direct influence on feature representation and code robustness. In three-dimensional simulations, modeling spherical volumes and features is particularly challenging for a hydrodynamics code. Calculations on traditional spherical meshes (such as spin meshes) often lead to errors and symmetry breaking. Although the underlying differencing scheme may be modified to rectify this, the differencing scheme may not be accessible. This work documents the use of spherical geodesic meshes to mitigate solution-mesh coupling. These meshes are generated notionally by connecting geodesic surface meshes to produce triangular-prismatic volume meshes. This mesh topology is fundamentally different from traditional mesh topologies and displays superior qualities such as topological symmetry. This work describes the geodesic mesh topology as well as motivating demonstrations with the FLAG hydrocode.

  15. The Spherical Deformation Model

    DEFF Research Database (Denmark)

    Hobolth, Asgar

    2003-01-01

    Miller et al. (1994) describe a model for representing spatial objects with no obvious landmarks. Each object is represented by a global translation and a normal deformation of a sphere. The normal deformation is defined via the orthonormal spherical-harmonic basis. In this paper we analyse...... the spherical deformation model in detail and describe how it may be used to summarize the shape of star-shaped three-dimensional objects with few parameters. It is of interest to make statistical inference about the three-dimensional shape parameters from continuous observations of the surface and from...

  16. CoPt and FePt magnetic alloys grown on van der Waals WSe{sub 2}(0001) surfaces and on arrays of SiO{sub 2} spherical particles

    Energy Technology Data Exchange (ETDEWEB)

    Makarov, Denys

    2008-06-06

    regard an interesting approach, which combines non-magnetic spherical nanoparticle self-assembly with defined magnetic properties provided by a magnetic film, deposited onto the particles, was recently proposed. This enables an elegant possibility of creating magnetic nanostructure arrays with high perpendicular magnetic anisotropy provided by FePt and CoPt alloys, which is required for high thermal stability. The investigation of the magnetic and structural properties of these alloys grown on arrays of amorphous SiO{sub 2} nanospheres is thereafter discussed. (orig.)

  17. Sensational spherical shells

    Science.gov (United States)

    Lee, M. C.; Kendall, J. M., Jr.; Bahrami, P. A.; Wang, T. G.

    1986-01-01

    Fluid-dynamic and capillary forces can be used to form nearly perfect, very small spherical shells when a liquid that can solidify is passed through an annular die to form an annular jet. Gravity and certain properties of even the most ideal materials, however, can cause slight asymmetries. The primary objective of the present work is the control of this shell formation process in earth laboratories rather than space microgravity, through the development of facilities and methods that minimize the deleterious effects of gravity, aerodynamic drag, and uncontrolled cooling. The spherical shells thus produced can be used in insulation, recyclable filter materials, fire retardants, explosives, heat transport slurries, shock-absorbing armor, and solid rocket motors.

  18. Clusters of polyhedra in spherical confinement

    Science.gov (United States)

    Teich, Erin G.; van Anders, Greg; Klotsa, Daphne; Dshemuchadse, Julia; Glotzer, Sharon C.

    2016-01-01

    Dense particle packing in a confining volume remains a rich, largely unexplored problem, despite applications in blood clotting, plasmonics, industrial packaging and transport, colloidal molecule design, and information storage. Here, we report densest found clusters of the Platonic solids in spherical confinement, for up to N=60 constituent polyhedral particles. We examine the interplay between anisotropic particle shape and isotropic 3D confinement. Densest clusters exhibit a wide variety of symmetry point groups and form in up to three layers at higher N. For many N values, icosahedra and dodecahedra form clusters that resemble sphere clusters. These common structures are layers of optimal spherical codes in most cases, a surprising fact given the significant faceting of the icosahedron and dodecahedron. We also investigate cluster density as a function of N for each particle shape. We find that, in contrast to what happens in bulk, polyhedra often pack less densely than spheres. We also find especially dense clusters at so-called magic numbers of constituent particles. Our results showcase the structural diversity and experimental utility of families of solutions to the packing in confinement problem. PMID:26811458

  19. Fundamentals of spherical array processing

    CERN Document Server

    Rafaely, Boaz

    2015-01-01

    This book provides a comprehensive introduction to the theory and practice of spherical microphone arrays. It is written for graduate students, researchers and engineers who work with spherical microphone arrays in a wide range of applications.   The first two chapters provide the reader with the necessary mathematical and physical background, including an introduction to the spherical Fourier transform and the formulation of plane-wave sound fields in the spherical harmonic domain. The third chapter covers the theory of spatial sampling, employed when selecting the positions of microphones to sample sound pressure functions in space. Subsequent chapters present various spherical array configurations, including the popular rigid-sphere-based configuration. Beamforming (spatial filtering) in the spherical harmonics domain, including axis-symmetric beamforming, and the performance measures of directivity index and white noise gain are introduced, and a range of optimal beamformers for spherical arrays, includi...

  20. Holographic Spherically Symmetric Metrics

    Science.gov (United States)

    Petri, Michael

    The holographic principle (HP) conjectures, that the maximum number of degrees of freedom of any realistic physical system is proportional to the system's boundary area. The HP has its roots in the study of black holes. It has recently been applied to cosmological solutions. In this article we apply the HP to spherically symmetric static space-times. We find that any regular spherically symmetric object saturating the HP is subject to tight constraints on the (interior) metric, energy-density, temperature and entropy-density. Whenever gravity can be described by a metric theory, gravity is macroscopically scale invariant and the laws of thermodynamics hold locally and globally, the (interior) metric of a regular holographic object is uniquely determined up to a constant factor and the interior matter-state must follow well defined scaling relations. When the metric theory of gravity is general relativity, the interior matter has an overall string equation of state (EOS) and a unique total energy-density. Thus the holographic metric derived in this article can serve as simple interior 4D realization of Mathur's string fuzzball proposal. Some properties of the holographic metric and its possible experimental verification are discussed. The geodesics of the holographic metric describe an isotropically expanding (or contracting) universe with a nearly homogeneous matter-distribution within the local Hubble volume. Due to the overall string EOS the active gravitational mass-density is zero, resulting in a coasting expansion with Ht = 1, which is compatible with the recent GRB-data.

  1. The ETE spherical Tokamak project

    Energy Technology Data Exchange (ETDEWEB)

    Ludwig, Gerson Otto; Andrade, Maria Celia Ramos de; Barbosa, Luis Filipe Wiltgen [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil). Lab. Associado de Plasma] [and others]. E-mail: ludwig@plasma.inpe.br

    1999-07-01

    This paper describes the general characteristics of spherical tokamaks, with a brief overview of work in the area of spherical torus already performed or in progress at several institutions. The paper presents also the historical development of the ETE (Spherical Tokamak Experiment) project, its research program, technical characteristics and status of construction in September, 1998 at the Associated plasma Laboratory (LAP) of the National Institute for Space Research (INPE) in Brazil. (author)

  2. Spherical tokamak development in Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Ludwig, Gerson Otto; Bosco, Edson Del; Ferreira, Julio Guimaraes [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil). Lab. Associado de Plasma] (and others)

    2003-07-01

    The general characteristics of spherical tokamaks, or spherical tori, with a brief view of work in this area already performed or in progress at several institutions worldwide are described. The paper presents also the steps in the development of the ETE (Experiment Tokamak spheric) project, its research program, technical characteristics and operating conditions as of December, 2002 a the Associated Plasma Laboratory (LAP) of the National Space Research Institute (INPE) in Brazil. (author)

  3. Computational spherical astronomy

    Science.gov (United States)

    Taff, Laurence G.

    The subject of the considered volume is the applied mathematics of spherical astronomy. The book is intended to aid those scientists and engineers, not trained in astrometry, to rapidly master the computational aspects of positional astronomy. Celestial coordinate systems are considered, taking into account the celestial sphere, the horizon system, the equatorial systems, the ecliptic system, the rotational transformations of celestial coordinates, position angle and distance, and special star positions. Other subjects discussed are related to general precession and proper motion, the parallax, the computation of the topocentric place, time systems, photographic astrometry, celestial mechanics, and astronomical catalogs. Attention is given to the power series method for the combined effects of general precession and proper motion, atomic time, the gravitational force, perturbation theory, solar system objects, stars, nonstellar objects, and the linear plate model.

  4. Pairing in spherical nanograins

    Energy Technology Data Exchange (ETDEWEB)

    Kuzmenko, N.K., E-mail: kuzmenko@NK9433.spb.ed [V.G. Khlopin Radium Institute, 2-nd Murinsky avenue 28, 194021 St.-Petersburg (Russian Federation); Mikhajlov, V.M. [Institute of Physics, St.-Petersburg State University, Ul' yanovskaya 3, 198904 Petergof (Russian Federation)

    2010-02-01

    Conditions are ascertained when the pairing and other thermodynamic properties of spherical nanograins with numbers of delocalized electrons N<10{sup 5} can be investigated by using the Single Shell Model (SSM) that gives the eigenvalues of the pairing Hamiltonian for a solitary shell. In the frame of SSM the exact canonical and grand canonical descriptions are employed first to analyze the absence of the abrupt superconducting-normal phase transition in finite systems in which an increase of the pairing and BCS critical temperature can be observed and secondly to study such new phenomena as the temperature re-entrance of the pairing in postcritical magnetic fields and also low temperature oscillations of the magnetic susceptibility and electronic heat capacity in an increasing uniform magnetic field.

  5. Spherical grating spectrometers

    Science.gov (United States)

    O'Donoghue, Darragh; Clemens, J. Christopher

    2014-07-01

    We describe designs for spectrometers employing convex dispersers. The Offner spectrometer was the first such instrument; it has almost exclusively been employed on satellite platforms, and has had little impact on ground-based instruments. We have learned how to fabricate curved Volume Phase Holographic (VPH) gratings and, in contrast to the planar gratings of traditional spectrometers, describe how such devices can be used in optical/infrared spectrometers designed specifically for curved diffraction gratings. Volume Phase Holographic gratings are highly efficient compared to conventional surface relief gratings; they have become the disperser of choice in optical / NIR spectrometers. The advantage of spectrometers with curved VPH dispersers is the very small number of optical elements used (the simplest comprising a grating and a spherical mirror), as well as illumination of mirrors off axis, resulting in greater efficiency and reduction in size. We describe a "Half Offner" spectrometer, an even simpler version of the Offner spectrometer. We present an entirely novel design, the Spherical Transmission Grating Spectrometer (STGS), and discuss exemplary applications, including a design for a double-beam spectrometer without any requirement for a dichroic. This paradigm change in spectrometer design offers an alternative to all-refractive astronomical spectrometer designs, using expensive, fragile lens elements fabricated from CaF2 or even more exotic materials. The unobscured mirror layout avoids a major drawback of the previous generation of catadioptric spectrometer designs. We describe laboratory measurements of the efficiency and image quality of a curved VPH grating in a STGS design, demonstrating, simultaneously, efficiency comparable to planar VPH gratings along with good image quality. The stage is now set for construction of a prototype instrument with impressive performance.

  6. Spherical agglomerates of lactose with enhanced mechanical properties.

    Science.gov (United States)

    Lamešić, Dejan; Planinšek, Odon; Lavrič, Zoran; Ilić, Ilija

    2017-01-10

    The aim of this study was to prepare spherical agglomerates of lactose and to evaluate their physicochemical properties, flow properties, particle friability and compaction properties, and to compare them to commercially available types of lactose for direct compression (spray-dried, granulated and anhydrous β-lactose). Porous spherical agglomerates of α-lactose monohydrate with radially arranged prism-like primary particles were prepared exhibiting a high specific surface area. All types of lactose analysed had passable or better flow properties, except for anhydrous β-lactose, which had poor flowability. Particle friability was more pronounced in larger granulated lactose particles; however, particle structure was retained in all samples analysed. The mechanical properties of spherical agglomerates of lactose, in terms of compressibility, established with Walker analysis, and compactibility, established with a compactibility profile, were found to be superior to any commercially available types of lactose. Higher compactibility of spherical agglomerates of lactose is ascribed to significantly higher particle surface area due to a unique internal structure with higher susceptibility to fragmentation. Copyright © 2016 Elsevier B.V. All rights reserved.

  7. Spherical wave rotation in spherical near-field antenna measurements

    DEFF Research Database (Denmark)

    Wu, Jian; Larsen, Flemming Holm; Lemanczyk, J.

    1991-01-01

    The rotation of spherical waves in spherical near-field antenna measurement is discussed. Considering the many difficult but interesting features of the rotation coefficients, an efficient rotation scheme is derived. The main feature of the proposed scheme is to ignore the calculation of the very...

  8. First results of spherical GEMs

    CERN Document Server

    Pinto, Serge Duarte; Brock, Ian; Croci, Gabriele; David, Eric; de Oliveira, Rui; Ropelewski, Leszek; van Stenis, Miranda; Taureg, Hans; Villa, Marco

    2010-01-01

    We developed a method to make GEM foils with a spherical geometry. Tests of this procedure and with the resulting spherical GEMs are presented. Together with a spherical drift electrode, a spherical conversion gap can be formed. This eliminates the parallax error for detection of x-rays, neutrons or UV photons when a gaseous converter is used. This parallax error limits the spatial resolution at wide scattering angles. Besides spherical GEMs, we have developed curved spacers to maintain accurate spacing, and a conical field cage to prevent edge distortion of the radial drift field up to the limit of the angular acceptance of the detector. With these components first tests are done in a setup with a spherical entrance window but a planar readout structure; results will be presented and discussed. A flat readout structure poses difficulties, however. Therefore we will show advanced plans to make a prototype of an entirely spherical double-GEM detector, including a spherical 2D readout structure. This detector w...

  9. Sound field reconstruciton using a spherical microphone array

    DEFF Research Database (Denmark)

    Fernandez Grande, Efren

    2016-01-01

    measurement area consisting of an array of spheres, and the sound field at any point of the source-free domain can be estimated, not being restricted to spherical surfaces. Because it is formulated as an elementary wave model, it allows for diverse solution strategies (least squares, ℓ1-norm minimization, etc......A method is presented that makes it possible to reconstruct an arbitrary sound field based on measurements with a spherical microphone array. The proposed method (spherical equivalent source method) makes use of a point source expansion to describe the sound field on the rigid spherical array, from...... which it is possible to reconstruct the sound field over a three-dimensional domain, inferring all acoustic quantities: sound pressure, particle velocity, and sound intensity. The problem is formulated using a Neumann Green's function that accounts for the presence of the rigid sphere in the medium. One...

  10. Effects of coating spherical iron oxide nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Milosevic, Irena; Motte, Laurence; Aoun, Bachir; Li, Tao; Ren, Yang; Sun, Chengjun; Saboungi, Marie-Louise

    2017-01-01

    We investigate the effect of several coatings applied in biomedical applications to iron oxide nanoparticles on the size, structure and composition of the particles. The four structural techniques employed - TEM, DLS, VSM, SAXS and EXAFS - show no significant effects of the coatings on the spherical shape of the bare nanoparticles, the average sizes or the local order around the Fe atoms. The NPs coated with hydroxylmethylene bisphosphonate or catechol have a lower proportion of magnetite than the bare and citrated ones, raising the question whether the former are responsible for increasing the valence state of the oxide on the NP surfaces and lowering the overall proportion of magnetite in the particles. VSM measurements show that these two coatings lead to a slightly higher saturation magnetization than the citrate. This article is part of a Special Issue entitled "Science for Life" Guest Editor: Dr. Austen Angell, Dr. Salvatore Magazu and Dr. Federica Migliardo.

  11. Gravitational field of spherical domain wall in higher dimension

    Indian Academy of Sciences (India)

    An exact solution of Einstein's equations is found describing the gravitational field of a spherical domain wall with nonvanishing stress component in the direction perpendicular to the plane of the wall. Also we have studied the motion of test particle around the domain wall.

  12. Spherically symmetric inhomogeneous bianisotropic media: Wave propagation and light scattering

    DEFF Research Database (Denmark)

    Novitsky, Andrey; Shalin, Alexander S.; Lavrinenko, Andrei

    2017-01-01

    We develop a technique for finding closed-form expressions for electromagnetic fields in radially inhomogeneous bianisotropic media, both the solutions of the Maxwell equations and material tensors being defined by the set of auxiliary two-dimensional matrices. The approach is applied to determin...... the scattering cross-sections by spherical particles, the fields inside which correspond to the Airy-exponential waves....

  13. Aerosol-Assisted Self-Assembly of Mesostructured Spherical Nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Brinker, C.J.; Fan,; H.; Lu, Y.; Rieker, T.; Stump, A.; Ward, T.L.

    1999-03-23

    Nanostructured particles exhibiting well-defined pore sizes and pore connectivities (1-, 2-, or 3-dimensional) are of interest for catalysis, chromatography, controlled release, low dielectric constant fillers, and custom-designed pigments and optical hosts. During the last several years considerable progress has been made on controlling the macroscopic forms of mesoporous silicas prepared by surfactant and block copolymer liquid crystalline templating procedures. Typically interfacial phenomena are used to control the macroscopic form (particles, fibers, or films), while self-assembly of amphiphilic surfactants or polymers is used to control the mesostructure. To date, although a variety of spherical or nearly-spherical particles have been prepared, their extent of order is limited as is the range of attainable mesostructures. They report a rapid, aerosol process that results in solid, completely ordered spherical particles with stable hexagonal, cubic, or vesicular mesostructures. The process relies on evaporation-induced interfacial self-assembly (EISA) confined to a spherical aerosol droplet. The process is simple and generalizable to a variety of materials combinations. Additionally, it can be modified to provide the first aerosol route to the formation of ordered mesostructured films.

  14. Spherically symmetric perfect fluid solutions

    Energy Technology Data Exchange (ETDEWEB)

    Hajj-Boutros, J.

    1985-04-01

    Many exact solutions for the spherically symmetric perfect fluid distribution of matter with shear, acceleration, and expansion are obtained. One of them is expressed in terms of Painleve's third transcendent.

  15. Toroidal equilibria in spherical coordinates

    OpenAIRE

    Tsui, K. H.

    2009-01-01

    The standard Grad-Shafranov equation for axisymmetric toroidal plasma equilibrium is customary expressed in cylindrical coordinates with toroidal contours, and through which benchmark equilibria are solved. An alternative approach to cast the Grad-Shafranov equation in spherical coordinates is presented. This equation, in spherical coordinates, is examined for toroidal solutions to describe low $\\beta$ Solovev and high $\\beta$ plasma equilibria in terms of elementary functions.

  16. Spherical tokamak development in Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Ludwig, G.O.; Del Bosco, E.; Ferreira, J.G.; Berni, L.A.; Oliveira, R.M.; Andrade, M.C.R.; Shibata, C.S.; Ueda, M.; Barroso, J.J.; Castro, P.J. [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil). Lab. Associado de Plasma; Barbosa, L.F.W. [Universidade do Vale do Paraiba (UNIVAP), Sao Jose dos Campos, SP (Brazil). Faculdade de Engenharia, Arquitetura e Urbanismo; Patire Junior, H. [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil). Div. de Mecanica Espacial e Controle; The high-power microwave sources group

    2003-12-01

    This paper describes the general characteristics of spherical tokamaks, or spherical tori, with a brief overview of work in this area already performed or in progress at several institutions worldwide. The paper presents also the steps in the development of the ETE (Experimento Tokamak Esferico) project, its research program, technical characteristics and operating conditions as of December, 2002 at the Associated Plasma Laboratory (LAP) of the National Space Research Institute (INPE) in Brazil. (author)

  17. Whispering gallery modes in a spherical microcavity with a photoluminescent shell

    Energy Technology Data Exchange (ETDEWEB)

    Grudinkin, S. A., E-mail: grudink@gvg.ioffe.ru; Dontsov, A. A.; Feoktistov, N. A. [Russian Academy of Sciences, Ioffe Physical–Technical Institute (Russian Federation); Baranov, M. A.; Bogdanov, K. V. [ITMO University (Russian Federation); Averkiev, N. S.; Golubev, V. G. [Russian Academy of Sciences, Ioffe Physical–Technical Institute (Russian Federation)

    2015-10-15

    Whispering-gallery mode spectra in optical microcavities based on spherical silica particles coated with a thin photoluminescent shell of hydrogenated amorphous silicon carbide are studied. The spectral positions of the whispering-gallery modes for spherical microcavities with a shell are calculated. The dependence of the spectral distance between the TE and TM modes on the shell thickness is examined.

  18. Application of different analytical methods for the characterization of non-spherical micro- and nanoparticles.

    Science.gov (United States)

    Mathaes, Roman; Winter, Gerhard; Engert, Julia; Besheer, Ahmed

    2013-09-10

    Non-spherical micro- and nanoparticles have recently gained considerable attention due to their surprisingly different interaction with biological systems compared to their spherical counterparts, opening new opportunities for drug delivery and vaccination. Up till now, electron microscopy is the only method to quantitatively identify the critical quality attributes (CQAs) of non-spherical particles produced by film-stretching; namely size, morphology and the quality of non-spherical particles (degree of contamination with spherical ones). However, electron microscopy requires expensive instrumentation, demanding sample preparation and non-trivial image analysis. To circumvent these drawbacks, the ability of different particle analysis methods to quantitatively identify the CQA of spherical and non-spherical poly(1-phenylethene-1,2-diyl (polystyrene) particles over a wide size range (40 nm, 2 μm and 10 μm) was investigated. To this end, light obscuration, image-based analysis methods (Microflow imaging, MFI, and Vi-Cell XR Coulter Counter) and flow cytometry were used to study particles in the micron range, while asymmetric flow field fractionation (AF4) coupled to multi-angle laser scattering (MALS) and quasi elastic light scattering (QELS) was used for particles in the nanometer range, and all measurements were benchmarked against electron microscopy. Results show that MFI can reliably identify particle size and aspect ratios of the 10 μm particles, but not the 2 μm ones. Meanwhile, flow cytometry was able to differentiate between spherical and non-spherical 10 or 2 μm particles, and determine the amount of impurities in the sample. As for the nanoparticles, AF4 coupled to MALS and QELS allowed the measurement of the geometric (rg) and hydrodynamic (rh) radii of the particles, as well as their shape factors (rg/rh), confirming their morphology. While this study shows the utility of MFI, flow cytometry and AF4 for quantitative evaluation of the CQA of non-spherical

  19. Explosive fragmentation of liquids in spherical geometry

    Science.gov (United States)

    Milne, A.; Longbottom, A.; Frost, D. L.; Loiseau, J.; Goroshin, S.; Petel, O.

    2017-05-01

    Rapid acceleration of a spherical shell of liquid following central detonation of a high explosive causes the liquid to form fine jets that are similar in appearance to the particle jets that are formed during explosive dispersal of a packed layer of solid particles. Of particular interest is determining the dependence of the scale of the jet-like structures on the physical parameters of the system, including the fluid properties (e.g., density, viscosity, and surface tension) and the ratio of the mass of the liquid to that of the explosive. The present paper presents computational results from a multi-material hydrocode describing the dynamics of the explosive dispersal process. The computations are used to track the overall features of the early stages of dispersal of the liquid layer, including the wave dynamics, and motion of the spall and accretion layers. The results are compared with new experimental results of spherical charges surrounded by a variety of different fluids, including water, glycerol, ethanol, and vegetable oil, which together encompass a significant range of fluid properties. The results show that the number of jet structures is not sensitive to the fluid properties, but primarily dependent on the mass ratio. Above a certain mass ratio of liquid fill-to-explosive burster ( F / B), the number of jets is approximately constant and consistent with an empirical model based on the maximum thickness of the accretion layer. For small values of F / B, the number of liquid jets is reduced, in contrast with explosive powder dispersal, where small F / B yields a larger number of particle jets. A hypothetical explanation of these features based on the nucleation of cavitation is explored numerically.

  20. Fluidization of spherocylindrical particles

    Science.gov (United States)

    Mahajan, Vinay V.; Nijssen, Tim M. J.; Fitzgerald, Barry W.; Hofman, Jeroen; Kuipers, Hans; Padding, Johan T.

    2017-06-01

    Multiphase (gas-solid) flows are encountered in numerous industrial applications such as pharmaceutical, food, agricultural processing and energy generation. A coupled computational fluid dynamics (CFD) and discrete element method (DEM) approach is a popular way to study such flows at a particle scale. However, most of these studies deal with spherical particles while in reality, the particles are rarely spherical. The particle shape can have significant effect on hydrodynamics in a fluidized bed. Moreover, most studies in literature use inaccurate drag laws because accurate laws are not readily available. The drag force acting on a non-spherical particle can vary considerably with particle shape, orientation with the flow, Reynolds number and packing fraction. In this work, the CFD-DEM approach is extended to model a laboratory scale fluidized bed of spherocylinder (rod-like) particles. These rod-like particles can be classified as Geldart D particles and have an aspect ratio of 4. Experiments are performed to study the particle flow behavior in a quasi-2D fluidized bed. Numerically obtained results for pressure drop and bed height are compared with experiments. The capability of CFD-DEM approach to efficiently describe the global bed dynamics for fluidized bed of rod-like particles is demonstrated.

  1. Fluidization of spherocylindrical particles

    Directory of Open Access Journals (Sweden)

    Mahajan Vinay V.

    2017-01-01

    Full Text Available Multiphase (gas-solid flows are encountered in numerous industrial applications such as pharmaceutical, food, agricultural processing and energy generation. A coupled computational fluid dynamics (CFD and discrete element method (DEM approach is a popular way to study such flows at a particle scale. However, most of these studies deal with spherical particles while in reality, the particles are rarely spherical. The particle shape can have significant effect on hydrodynamics in a fluidized bed. Moreover, most studies in literature use inaccurate drag laws because accurate laws are not readily available. The drag force acting on a non-spherical particle can vary considerably with particle shape, orientation with the flow, Reynolds number and packing fraction. In this work, the CFD-DEM approach is extended to model a laboratory scale fluidized bed of spherocylinder (rod-like particles. These rod-like particles can be classified as Geldart D particles and have an aspect ratio of 4. Experiments are performed to study the particle flow behavior in a quasi-2D fluidized bed. Numerically obtained results for pressure drop and bed height are compared with experiments. The capability of CFD-DEM approach to efficiently describe the global bed dynamics for fluidized bed of rod-like particles is demonstrated.

  2. Spherical agglomeration of acetylsalicylic acid

    Directory of Open Access Journals (Sweden)

    Polowczyk Izabela

    2016-01-01

    Full Text Available In this paper spherical agglomeration of acetylsalicylic acid was described. In the first step, the system of good and poor solvents as well as bridging liquid was selected. As a result of a preliminary study, ethyl alcohol, water and carbon tetrachloride were used as the good solvent, poor one, and bridging liquid, respectively. Then, the amount of acetylsalicylic acid and the ratio of the solvents as well as the volume of the bridging liquid were examined. In the last step, the agglomeration conditions, such as mixing intensity and time, were investigated. The spherical agglomerates obtained under optimum conditions could be subjected to a tableting process afterwards.

  3. Basketballs as spherical acoustic cavities

    Science.gov (United States)

    Russell, Daniel A.

    2010-06-01

    The sound field resulting from striking a basketball is found to be rich in frequency content, with over 50 partials in the frequency range of 0-12 kHz. The frequencies are found to closely match theoretical expectations for standing wave patterns inside a spherical cavity. Because of the degenerate nature of the mode shapes, explicit identification of the modes is not possible without internal investigation with a microphone probe. A basketball proves to be an interesting application of a boundary value problem involving spherical coordinates.

  4. Processes for making dense, spherical active materials for lithium-ion cells

    Science.gov (United States)

    Kang, Sun-Ho [Naperville, IL; Amine, Khalil [Downers Grove, IL

    2011-11-22

    Processes are provided for making dense, spherical mixed-metal carbonate or phosphate precursors that are particularly well suited for the production of active materials for electrochemical devices such as lithium ion secondary batteries. Exemplified methods include precipitating dense, spherical particles of metal carbonates or metal phosphates from a combined aqueous solution using a precipitating agent such as ammonium hydrogen carbonate, sodium hydrogen carbonate, or a mixture that includes sodium hydrogen carbonate. Other exemplified methods include precipitating dense, spherical particles of metal phosphates using a precipitating agent such as ammonium hydrogen phosphate, ammonium dihydrogen phosphate, sodium phosphate, sodium hydrogen phosphate, sodium dihydrogen phosphate, or a mixture of any two or more thereof. Further provided are compositions of and methods of making dense, spherical metal oxides and metal phosphates using the dense, spherical metal precursors. Still further provided are electrodes and batteries using the same.

  5. Mechanisms of Stochastic Diffusion of Energetic Ions in Spherical Tori

    Energy Technology Data Exchange (ETDEWEB)

    Ya.I. Kolesnichenko; R.B. White; Yu.V. Yakovenko

    2001-01-18

    Stochastic diffusion of the energetic ions in spherical tori is considered. The following issues are addressed: (I) Goldston-White-Boozer diffusion in a rippled field; (ii) cyclotron-resonance-induced diffusion caused by the ripple; (iii) effects of non-conservation of the magnetic moment in an axisymmetric field. It is found that the stochastic diffusion in spherical tori with a weak magnetic field has a number of peculiarities in comparison with conventional tokamaks; in particular, it is characterized by an increased role of mechanisms associated with non-conservation of the particle magnetic moment. It is concluded that in current experiments on National Spherical Torus eXperiment (NSTX) the stochastic diffusion does not have a considerable influence on the confinement of energetic ions.

  6. Spherical Pendulum, Actions, and Spin

    NARCIS (Netherlands)

    Richter, Peter H.; Dullin, Holger R.; Waalkens, Holger; Wiersig, Jan

    1996-01-01

    The classical and quantum mechanics of a spherical pendulum are worked out, including the dynamics of a suspending frame with moment of inertia θ. The presence of two separatrices in the bifurcation diagram of the energy-momentum mapping has its mathematical expression in the hyperelliptic nature of

  7. Strichartz Estimates in Spherical Coordinates

    OpenAIRE

    Cho, Yonggeun; Lee, Sanghyuk

    2012-01-01

    In this paper we study Strichartz estimates for dispersive equations which are defined by radially symmetric pseudo-differential operators, and of which initial data belongs to spaces of Sobolev type defined in spherical coordinates. We obtain the space time estimates on the best possible range including the endpoint cases.

  8. Timelike geodesics around a charged spherically symmetric dilaton black hole

    Directory of Open Access Journals (Sweden)

    Blaga C.

    2015-01-01

    Full Text Available In this paper we study the timelike geodesics around a spherically symmetric charged dilaton black hole. The trajectories around the black hole are classified using the effective potential of a free test particle. This qualitative approach enables us to determine the type of orbit described by test particle without solving the equations of motion, if the parameters of the black hole and the particle are known. The connections between these parameters and the type of orbit described by the particle are obtained. To visualize the orbits we solve numerically the equation of motion for different values of parameters envolved in our analysis. The effective potential of a free test particle looks different for a non-extremal and an extremal black hole, therefore we have examined separately these two types of black holes.

  9. Mechanical characterization of ibuprofen, naproxen, and their spherically crystallized products

    Science.gov (United States)

    Anderson, Stephen R.

    The objectives of this study were to establish a rational basis for choosing parameters for conducting the tensile strength and indentation hardness test on pharmaceutical compacts, to describe the changes in tableting indices based on the different parameters, to develop a method to spherically crystallize ibuprofen, and to compare the mechanical and micromeritic properties of spherically crystallized ibuprofen and naproxen to the starting materials. This work described the importance of establishing the appropriate test parameters for tensile strength and indentation hardness tests so that reliable and predictive tableting indices could be determined. The fracture strength for diametral compression of ibuprofen compacts was determined for two modes of stress application, constant stress rate and constant strain rate. The tensile strength for diametral compression of ibuprofen and naproxen compacts was determined using a constant strain rate (0.05 to 16 mm/min). The static indentation hardness (Meyer hardness) of ibuprofen and naproxen compacts was determined at varying solid fractions and indentor depth of penetration. Results from these studies were used to establish an appropriate rate of stress application during diametral compression and an appropriate depth of penetration for indentation hardness testing in order to calculate tableting indices. The tableting indices calculated from the aforementioned properties were: the brittle fracture index (BFI), the best case bonding index (BIsb{b}), the worst case bonding index (BIsb{w}), the brittle/viscoelastic bonding index (bBIsb{v}), and the viscoelastic index (VI). In addition, changes in compactibility between the starting materials and their spherically crystallized products were assessed through the analysis of Athy-Heckel profiles. A comparison of micromeritic properties included particle size, porosity, surface area, bulk density, tap density, true density, and flowability as measured by the Carr Index. The

  10. Miniaturization of Spherical Magnetodielectric Antennas

    DEFF Research Database (Denmark)

    Hansen, Troels Vejle

    The fundamental limitations in performance of electrically small antennas (ESAs) - and how far these may be approached - have been of great interest for over a century. Particularly over the past few decades, it has become increasingly relevant and important, to approach these limits in view...... to the important antenna parameters of radiation efficiency e and impedance bandwidth. For single-mode antennas the fundamental minimum Q is the Chu lower bound. In this Ph.D. dissertation, the topic is miniaturization of spherical antennas loaded by an internal magnetodielectric core. The goal is to determine......, quantify, and assess the effects of an internal material loading upon antenna performance, including its potentials towards miniaturization. Emphasis have been upon performing an exhaustive and exact analysis of rigorous validity covering a large class of spherical antennas. In the context of this study...

  11. The Electrochemical Behavior of Dispersions of Spherical Ultramicroelectrodes.

    Science.gov (United States)

    1986-07-30

    means of bipolar electrolyses with dispersions. Polarization equations are predicted for highly simplified models based on the concept of the mixture...three-dimensional electrodes. Bipolar electrolyses on dispersions of spherical particles have been proposed and the behavior of such electrodes in the... electrolyses (I0řcm < a < j0-3cm) is intermediate to that of the colloidal systems (typically 10- 6cm) and fluidized bed electrodes (typically 10- 2cm

  12. Effects of coating spherical iron oxide nanoparticles.

    Science.gov (United States)

    Milosevic, Irena; Motte, Laurence; Aoun, Bachir; Li, Tao; Ren, Yang; Sun, Chengjun; Saboungi, Marie-Louise

    2017-01-01

    We investigate the effect of several coatings applied in biomedical applications to iron oxide nanoparticles on the size, structure and composition of the particles. The four structural techniques employed - TEM, DLS, VSM, SAXS and EXAFS - show no significant effects of the coatings on the spherical shape of the bare nanoparticles, the average sizes or the local order around the Fe atoms. The NPs coated with hydroxylmethylene bisphosphonate or catechol have a lower proportion of magnetite than the bare and citrated ones, raising the question whether the former are responsible for increasing the valence state of the oxide on the NP surfaces and lowering the overall proportion of magnetite in the particles. VSM measurements show that these two coatings lead to a slightly higher saturation magnetization than the citrate. This article is part of a Special Issue entitled "Science for Life" Guest Editor: Dr. Austen Angell, Dr. Salvatore Magazù and Dr. Federica Migliardo. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. ICPP: Results from the MAST Spherical Tokamak

    Science.gov (United States)

    Sykes, Alan

    2000-10-01

    The MAST (Mega-Amp Spherical Tokamak) experiment is now fully operational, producing 1MA plasmas with MW level auxiliary heating from Neutral Beam Injection and 60GHz Electron Cyclotron Resonance Heating. Central electron and ion temperatures are both of order 1keV (measured by 30-point Thomson Scattering, Neutral Particle Analyzer and Charge-Exchange spectroscopy respectively). Following boronisation, the Greenwald density limit has been exceeded in double-null divertor discharges by 50operation has been achieved in both Ohmic and NBI heated plasmas. In addition to conventional plasma induction, MAST can employ the `merging-compression' scheme (pioneered on START) producing initial spherical tokamak plasmas of up to 0.5MA without use of flux from the central solenoid. The central solenoid can then be applied to further increase the current at ramp rates of up to 13MA/s; plasma current of 1MA is reached at only one-half of the full solenoid swing. Studies of strike point power loading in both Ohmic and beam heated plasmas have confirmed the result from START that the fraction of power loading on the inboard strike point is lower than predicted from simple models. Comprehensive arrays of halo detectors indicate tolerable levels of halo currents with low asymmetries; an encouraging result for the ST concept, and providing key data to test models. Results from MAST will be used both to extend the conventional tokamak database, and to determine the potential of the ST as a route to fusion power in its own right. Acknowledgement: this work is funded jointly by the UK Department of Trade and Industry and EURATOM. The NBI equipment is on loan from ORNL, the NPA from PPPL.

  14. Definition of a solvent system for spherical crystallization of salbutamol sulfate by quasi-emulsion solvent diffusion (QESD) method.

    Science.gov (United States)

    Nocent, M; Bertocchi, L; Espitalier, F; Baron, M; Couarraze, G

    2001-10-01

    In this paper we describe how the spherical crystallization process by QESD method can be applied to a water-soluble drug, salbutamol sulfate. The type of solvent, antisolvent, and emulsifier and the concentration of emulsifier to be used for the production of spherical particles with a size range 80-500 microm are determined. Furthermore, the solvent/antisolvent ratio and the temperature difference between them (Delta T) are studied. It was observed that, in the case of salbutamol sulfate, the Delta T value has no influence on the formation of spherical particles. A very large metastable zone of salbutamol sulfate in water could explain this phenomenon. Finally, the influence of emulsifier concentration and of maturation time on the size of spherical particles is studied. The results show that these two parameters must be fixed to control the size of the recovered particles. Copyright 2001 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 90:1620-1627, 2001

  15. Progress in octahedral spherical hohlraum study

    Directory of Open Access Journals (Sweden)

    Ke Lan

    2016-01-01

    Full Text Available In this paper, we give a review of our theoretical and experimental progress in octahedral spherical hohlraum study. From our theoretical study, the octahedral spherical hohlraums with 6 Laser Entrance Holes (LEHs of octahedral symmetry have robust high symmetry during the capsule implosion at hohlraum-to-capsule radius ratio larger than 3.7. In addition, the octahedral spherical hohlraums also have potential superiority on low backscattering without supplementary technology. We studied the laser arrangement and constraints of the octahedral spherical hohlraums, and gave a design on the laser arrangement for ignition octahedral hohlraums. As a result, the injection angle of laser beams of 50°–60° was proposed as the optimum candidate range for the octahedral spherical hohlraums. We proposed a novel octahedral spherical hohlraum with cylindrical LEHs and LEH shields, in order to increase the laser coupling efficiency and improve the capsule symmetry and to mitigate the influence of the wall blowoff on laser transport. We studied on the sensitivity of the octahedral spherical hohlraums to random errors and compared the sensitivity among the octahedral spherical hohlraums, the rugby hohlraums and the cylindrical hohlraums, and the results show that the octahedral spherical hohlraums are robust to these random errors while the cylindrical hohlraums are the most sensitive. Up till to now, we have carried out three experiments on the spherical hohlraum with 2 LEHs on Shenguang(SG laser facilities, including demonstration of improving laser transport by using the cylindrical LEHs in the spherical hohlraums, spherical hohlraum energetics on the SGIII prototype laser facility, and comparisons of laser plasma instabilities between the spherical hohlraums and the cylindrical hohlraums on the SGIII laser facility.

  16. preparation of spherical polymeric particles from tanzanian cashew

    African Journals Online (AJOL)

    Starch = 1.3 g. 60. CNSL[40] SgP. CNSL = 10 g formalin =10 ml. 7% NaOH. = 3 ml. 600. Mg(OH)2 = 1 g. BaSO4 = 0.5 g. 55. B.P = Benzoyl peroxide; in each recipe 2-3 ml of dodecyl alcohol was added as a porogen. During SPP preparation, it was noted that use of large volume of monomer in the recipe relative to the ...

  17. Spherical sila- and germa-homoaromaticity.

    Science.gov (United States)

    Chen, Zhongfang; Hirsch, Andreas; Nagase, Shigeru; Thiel, Walter; Schleyer, Paul von Ragué

    2003-12-17

    Guided by the 2(N + 1)2 electron-counting rule for spherical aromatic molecules, we have designed various spherical sila- and germa-homoaromatic systems rich in group 14 elements. Their aromaticity is revealed by density-functional computations of their structures and the nucleus-independent chemical shifts (NICS). Besides the formerly used endohedral inclusion strategy, spherical homoaromaticity is another way to stabilize silicon and germanium clusters.

  18. The ETE spherical Tokamak project. IAEA report

    Energy Technology Data Exchange (ETDEWEB)

    Ludwig, Gerson Otto; Del Bosco, E.; Berni, L.A.; Ferreira, J.G.; Oliveira, R.M.; Andrade, M.C.R.; Shibata, C.S.; Barroso, J.J.; Castro, P.J.; Patire Junior, H. [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil). Lab. Associado de Plasma]. E-mail: ludwig@plasma.inpe.br

    2002-07-01

    This paper describes the general characteristics of spherical tokamaks, or spherical tori, with a brief overview of work in this area already performed or in progress at several institutions worldwide. The paper presents also the historical development of the ETE (Spherical Tokamak Experiment) project, its research program, technical characteristics and operating conditions as of October, 2002 at the Associated Plasma Laboratory (LAP) of the National Space Research Institute (INPE) in Brazil. (author)

  19. Measuring Spherical Harmonic Coefficients on a Sphere

    Energy Technology Data Exchange (ETDEWEB)

    Pollaine, S; Haan, S W

    2003-05-16

    The eigenfunctions of Rayleigh-Taylor modes on a spherical capsule are the spherical harmonics Y{sub l,m} These can be measured by measuring the surface perturbations along great circles and fitting them to the first few modes by a procedure described in this article. For higher mode numbers, it is more convenient to average the Fourier power spectra along the great circles, and then transform them to spherical harmonic modes by an algorithm derived here.

  20. Spherical Collapse in Chameleon Models

    CERN Document Server

    Brax, Ph; Steer, D A

    2010-01-01

    We study the gravitational collapse of an overdensity of nonrelativistic matter under the action of gravity and a chameleon scalar field. We show that the spherical collapse model is modified by the presence of a chameleon field. In particular, we find that even though the chameleon effects can be potentially large at small scales, for a large enough initial size of the inhomogeneity the collapsing region possesses a thin shell that shields the modification of gravity induced by the chameleon field, recovering the standard gravity results. We analyse the behaviour of a collapsing shell in a cosmological setting in the presence of a thin shell and find that, in contrast to the usual case, the critical density for collapse depends on the initial comoving size of the inhomogeneity.

  1. Towards Non-spherical Radio Models

    Science.gov (United States)

    Ribeiro, V. A. R. M.; Steffen, W.; Chomiuk, L.; Koning, N.; O'Brien, T. J.; Woudt, P. A.

    2014-12-01

    Radio observations of novae in outburst are of particular interest due to the physical parameters that may be retrieved from fitting the radio light curves. Most models that have fitted previous data assumed spherical symmetry however, it is becoming more and more clear that this is not the case. We explore morpho-kinematical techniques to retrieve the free-free radio light curves of non-spherical models and explore the effects of a non-spherical outburst on the physical parameters. In particular, we find that we may have been over estimating the ejected masses in the outburst of non-spherical novae.

  2. The geometry of spherical space form groups

    CERN Document Server

    Gilkey, Peter B

    1989-01-01

    In this volume, the geometry of spherical space form groups is studied using the eta invariant. The author reviews the analytical properties of the eta invariant of Atiyah-Patodi-Singer and describes how the eta invariant gives rise to torsion invariants in both K-theory and equivariant bordism. The eta invariant is used to compute the K-theory of spherical space forms, and to study the equivariant unitary bordism of spherical space forms and the Pin c and Spin c equivariant bordism groups for spherical space form groups. This leads to a complete structure theorem for these bordism and K-theor

  3. Simulation of spatial distribution of absorbed laser energy in spherical microcapsules

    Science.gov (United States)

    Geints, Yu E.; Zemlyanov, A. A.; Panina, E. K.

    2016-09-01

    Specific features of optical field distribution in composite spherical particles consisting of a liquid core and nanocomposite absorbing shell are theoretically studied at different wavelengths of incident radiation. Using the numerical simulation it is shown that the thickness of the shell of the spherical microcapsule particle and its intrinsic absorption coefficient determine the character of the spatial distribution and the absorbed power. The variation of these parameters allows one to change the spatial position of efficient volume absorption regions and peak absorption values. This provides favourable conditions for opening the shells in appropriate spatial zones to release the contents of the microcapsules.

  4. Morphology-Dependent Resonances of Spherical Droplets with Numerous Microscopic Inclusions

    Science.gov (United States)

    Mishchenko, Michael I.; Liu, Li; Mackowski, Daniel W.

    2014-01-01

    We use the recently extended superposition T-matrix method to study the behavior of a sharp Lorenz-Mie resonance upon filling a spherical micrometer-sized droplet with tens and hundreds of randomly positioned microscopic inclusions. We show that as the number of inclusions increases, the extinction cross-section peak and the sharp asymmetry-parameter minimum become suppressed, widen, and move toward smaller droplet size parameters, while ratios of diagonal elements of the scattering matrix exhibit sharp angular features indicative of a distinctly nonspherical particle. Our results highlight the limitedness of the concept of an effective refractive index of an inhomogeneous spherical particle.

  5. Numerical modeling of molecular-motor-assisted transport of adenoviral vectors in a spherical cell.

    Science.gov (United States)

    Kuznetsov, A V; Avramenko, A A; Blinov, D G

    2008-06-01

    Viral gene delivery in a spherical cell is investigated numerically. The model of intracellular trafficking of adenoviruses is based on molecular-motor-assisted transport equations suggested by Smith and Simmons. These equations are presented in spherical coordinates and extended by accounting for the random component of motion of viral particles bound to filaments. This random component is associated with the stochastic nature of molecular motors responsible for locomotion of viral particles bound to filaments. The equations are solved numerically to simulate viral transport between the cell membrane and cell nucleus during initial stages of viral infection.

  6. Controlled electrosprayed formation of non-spherical microparticles

    Science.gov (United States)

    Jeyhani, Morteza; Mak, Sze Yi; Sammut, Stephen; Shum, Ho Cheung; Hwang, Dae Kun; Tsai, Scott S. H.

    2017-11-01

    Fabrication of biocompatible microparticles, such as alginate particles, with the possibility of controlling the particles' morphology in a high-throughput manner, is essential for pharmaceutical and cosmetic industries. Even though the shape of alginate particles has been shown to be an important parameter in controlling drug delivery, there are very limited manufacturing methods to produce non-spherical alginate microparticles in a high-throughput fashion. Here, we present a system that generates non-spherical biocompatible alginate microparticles with a tunable size and shape, and at high-throughput, using an electrospray technique. Alginate solution, which is a highly biocompatible material, is flown through a needle using a constant flow rate syringe pump. The alginate phase is connected to a high-voltage power supply to charge it positively. There is a metallic ring underneath the needle that is charged negatively. The applied voltage creates an electric field that forces the dispensing droplets to pass through the metallic ring toward the collection bath. During this migration, droplets break up to smaller droplets to dissipate their energy. When the droplets reach the calcium chloride bath, polymerization happens and solidifies the droplets. We study the effects of changing the distance from the needle to the bath, and the concentration of calcium chloride in the bath, to control the size and the shape of the resulting microparticles.

  7. How Spherical Is a Cube (Gravitationally)?

    Science.gov (United States)

    Sanny, Jeff; Smith, David

    2015-01-01

    An important concept that is presented in the discussion of Newton's law of universal gravitation is that the gravitational effect external to a spherically symmetric mass distribution is the same as if all of the mass of the distribution were concentrated at the center. By integrating over ring elements of a spherical shell, we show that the…

  8. Sharp Strichartz estimates in spherical coordinates

    OpenAIRE

    Schippa, Robert

    2016-01-01

    We prove almost Strichartz estimates found after adding regularity in the spherical coordinates for Schr\\"odinger-like equations. The estimates are sharp up to endpoints. The proof relies on estimates involving spherical averages. Sharpness is discussed making use of a modified Knapp-type example.

  9. Statistical mechanics of thin spherical shells

    CERN Document Server

    Kosmrlj, Andrej

    2016-01-01

    We explore how thermal fluctuations affect the mechanics of thin amorphous spherical shells. In flat membranes with a shear modulus, thermal fluctuations increase the bending rigidity and reduce the in-plane elastic moduli in a scale-dependent fashion. This is still true for spherical shells. However, the additional coupling between the shell curvature, the local in-plane stretching modes and the local out-of-plane undulations, leads to novel phenomena. In spherical shells thermal fluctuations produce a radius-dependent negative effective surface tension, equivalent to applying an inward external pressure. By adapting renormalization group calculations to allow for a spherical background curvature, we show that while small spherical shells are stable, sufficiently large shells are crushed by this thermally generated "pressure". Such shells can be stabilized by an outward osmotic pressure, but the effective shell size grows non-linearly with increasing outward pressure, with the same universal power law expone...

  10. Scaling of a fast spherical discharge

    Science.gov (United States)

    Antsiferov, P. S.; Dorokhin, L. A.

    2017-02-01

    The influence of the discharge cavity dimensions on the properties of the spherical plasma formed in a fast discharge was studied experimentally. The passage of a current pulse with an amplitude of 30-40 kA and a rise rate of 1012 A/s (a fast discharge) through a spherical ceramic (Al2O3) cavity with an inner diameter of 11 mm filled with argon at a pressure of 80 Pa results in the formation of a 1- to 2-mm-diameter spherical plasma with an electron temperature of several tens of electronvolts and a density of 1018-1019 cm-3. It is shown that an increase in the inner diameter of the discharge cavity from 11 to 21 mm leads to the fourfold increase in the formation time of the spherical plasma and a decrease in the average ion charge. A decrease in the cavity diameter to 7 mm makes the spherical plasma unstable.

  11. Minimal Length Effects on Tunnelling from Spherically Symmetric Black Holes

    Directory of Open Access Journals (Sweden)

    Benrong Mu

    2015-01-01

    Full Text Available We investigate effects of the minimal length on quantum tunnelling from spherically symmetric black holes using the Hamilton-Jacobi method incorporating the minimal length. We first derive the deformed Hamilton-Jacobi equations for scalars and fermions, both of which have the same expressions. The minimal length correction to the Hawking temperature is found to depend on the black hole’s mass and the mass and angular momentum of emitted particles. Finally, we calculate a Schwarzschild black hole's luminosity and find the black hole evaporates to zero mass in infinite time.

  12. CMB Anisotropy of Spherical Spaces

    CERN Document Server

    Aurich, Ralf; Steiner, Frank

    2005-01-01

    The first-year WMAP data taken at their face value hint that the Universe might be slightly positively curved and therefore necessarily finite, since all spherical (Clifford-Klein) space forms M^3 = S^3/Gamma, given by the quotient of S^3 by a group Gamma of covering transformations, possess this property. We examine the anisotropy of the cosmic microwave background (CMB) for all typical groups Gamma corresponding to homogeneous universes. The CMB angular power spectrum and the temperature correlation function are computed for the homogeneous spaces as a function of the total energy density parameter Omega_tot in the large range [1.01, 1.20] and are compared with the WMAP data. We find that out of the infinitely many homogeneous spaces only the three corresponding to the binary dihedral group T*, the binary octahedral group O*, and the binary icosahedral group I* are in agreement with the WMAP observations. Furthermore, if Omega_tot is restricted to the interval [1.00, 1.04], the space described by T* is excl...

  13. Spherically symmetric charged compact stars

    Energy Technology Data Exchange (ETDEWEB)

    Maurya, S.K. [University of Nizwa, Department of Mathematical and Physical Sciences, College of Arts and Science, Nizwa (Oman); Gupta, Y.K. [Jaypee Institute of Information Technology University, Department of Mathematics, Noida, Uttar Pradesh (India); Ray, Saibal [Government College of Engineering and Ceramic Technology, Department of Physics, Kolkata, West Bengal (India); Chowdhury, Sourav Roy [Seth Anandaram Jaipuria College, Department of Physics, Kolkata, West Bengal (India)

    2015-08-15

    In this article we consider the static spherically symmetric metric of embedding class 1. When solving the Einstein-Maxwell field equations we take into account the presence of ordinary baryonic matter together with the electric charge. Specific new charged stellar models are obtained where the solutions are entirely dependent on the electromagnetic field, such that the physical parameters, like density, pressure etc. do vanish for the vanishing charge. We systematically analyze altogether the three sets of Solutions I, II, and III of the stellar models for a suitable functional relation of ν(r). However, it is observed that only the Solution I provides a physically valid and well-behaved situation, whereas the Solutions II and III are not well behaved and hence not included in the study. Thereafter it is exclusively shown that the Solution I can pass through several standard physical tests performed by us. To validate the solution set presented here a comparison has also been made with that of the compact stars, like RX J 1856 - 37, Her X - 1, PSR 1937+21, PSRJ 1614-2230, and PSRJ 0348+0432, and we have shown the feasibility of the models. (orig.)

  14. Fast calculation of spherical computer generated hologram using spherical wave spectrum method.

    Science.gov (United States)

    Jackin, Boaz Jessie; Yatagai, Toyohiko

    2013-01-14

    A fast calculation method for computer generation of spherical holograms in proposed. This method is based on wave propagation defined in spectral domain and in spherical coordinates. The spherical wave spectrum and transfer function were derived from boundary value solutions to the scalar wave equation. It is a spectral propagation formula analogous to angular spectrum formula in cartesian coordinates. A numerical method to evaluate the derived formula is suggested, which uses only N(logN)2 operations for calculations on N sampling points. Simulation results are presented to verify the correctness of the proposed method. A spherical hologram for a spherical object was generated and reconstructed successfully using the proposed method.

  15. Spherical magnetic nanoparticles fabricated by laser target evaporation

    Science.gov (United States)

    Safronov, A. P.; Beketov, I. V.; Komogortsev, S. V.; Kurlyandskaya, G. V.; Medvedev, A. I.; Leiman, D. V.; Larrañaga, A.; Bhagat, S. M.

    2013-05-01

    Magnetic nanoparticles of iron oxide (MNPs) were prepared by the laser target evaporation technique (LTE). The main focus was on the fabrication of de-aggregated spherical maghemite MNPs with a narrow size distribution and enhanced effective magnetization. X-ray diffraction, transmission electron microscopy, magnetization and microwave absorption measurements were comparatively analyzed. The shape of the MNPs (mean diameter of 9 nm) was very close to being spherical. The lattice constant of the crystalline phase was substantially smaller than that of stoichiometric magnetite but larger than the lattice constant of maghemite. High value of Ms up to 300 K was established. The 300 K ferromagnetic resonance signal is a single line located at a field expected from spherical magnetic particles with negligible magnetic anisotropy. The maximum obtained concentration of water based ferrofluid was as high as 10g/l of magnetic material. In order to understand the temperature and field dependence of MNPs magnetization, we invoke the core-shell model. The nanoparticles is said to have a ferrimagnetic core (roughly 70 percent of the caliper size) while the shell consists of surface layers in which the spins are frozen having no long range magnetic order. The core-shell interactions were estimated in frame of random anisotropy model. The obtained assembly of de-aggregated nanoparticles is an example of magnetic nanofluid stable under ambient conditions even without an electrostatic stabilizer.

  16. Spherical aberration in contact lens wear.

    Science.gov (United States)

    Lindskoog Pettersson, A; Jarkö, C; Alvin, A; Unsbo, P; Brautaset, R

    2008-08-01

    The aim of the present studies was to investigate the effect on spherical aberration of different non custom-made contact lenses, both with and without aberration control. A wavefront analyser (Zywave, Bausch & Lomb) was used to measure the aberrations in each subject's right eye uncorrected and with the different contact lenses. The first study evaluated residual spherical aberration with a standard lens (Focus Dailies Disposable, Ciba Vision) and with an aberration controlled contact lens (ACCL) (Definition AC, Optical Connection Inc.). The second study evaluated the residual spherical aberrations with a monthly disposable silicone hydrogel lens with aberration reduction (PureVision, Bausch & Lomb). Uncorrected spherical aberration was positive for all pupil sizes in both studies. In the first study, residual spherical aberration was close to zero with the standard lens for all pupil sizes whereas the ACCL over-corrected spherical aberration. The results of the second study showed that the monthly disposable lens also over-corrected the aberration making it negative. The changes in aberration were statistically significant (plenses. Since the amount of aberration varies individually we suggest that aberrations should be measured with lenses on the eye if the aim is to change spherical aberration in a certain direction.

  17. Novel Electrically Small Spherical Electric Dipole Antenna

    DEFF Research Database (Denmark)

    Kim, Oleksiy S.

    2010-01-01

    This paper introduces a novel electrically small spherical meander antenna. Horizontal sections of the meander are composed of wire loops, radii of which are chosen so that the whole structure is conformal to a sphere of radius a. To form the meander the loops are connected by wires at a meridian...... plane. The antenna operates as an electric dipole, i.e. it radiates the TM10 spherical mode. The antenna is self-resonant and can be matched to a wide range of input feed lines without an external matching network. In this paper, a spherical meander antenna of the size ka = 0.27 and the input impedance...

  18. Microstructure and rheology of particle stabilized emulsions: Effects of particle shape and inter-particle interactions.

    Science.gov (United States)

    Katepalli, Hari; John, Vijay T; Tripathi, Anubhav; Bose, Arijit

    2017-01-01

    Using fumed and spherical silica particles of similar hydrodynamic size, we investigated the effects of particle shape and inter-particle interactions on the formation, stability and rheology of bromohexadecane-in-water Pickering emulsions. The interparticle interactions were varied from repulsive to attractive by modifying the salt concentration in the aqueous phase. Optical microscope images revealed smaller droplet sizes for the fumed silica stabilized emulsions. All the emulsions remained stable for several weeks. Cryo-SEM images of the emulsion droplets showed a hexagonally packed single layer of particles at oil-water interfaces in emulsions stabilized with silica spheres, irrespective of the nature of the inter-particle interactions. Thus, entropic, excluded volume interactions dominate the fate of spherical particles at oil-water interfaces. On the other hand, closely packed layers of particles were observed at oil-water interfaces for the fumed silica stabilized emulsions for both attractive and repulsive interparticle interactions. At the high salt concentrations, attractive inter-particles interactions led to aggregation of fumed silica particles, and multiple layers of these particles were then observed on the droplet surfaces. A network of fumed silica particles was also observed between the emulsion droplets, suggesting that enthalpic interactions are responsible for the determining particle configurations at oil-water interfaces as well as in the aqueous phase. Steady shear viscosity measurements over a range of shear stresses, as well as oscillatory shear measurements at 1Hz confirm the presence of a network in fumed silica suspensions and emulsions, and the lack of such a network when spherical particles are used. The fractal structure of fumed silica leads to several contact points and particle interlocking in the water as well as on the bromohexadecane-water interfaces, with corresponding effects on the structure and rheology of the emulsions

  19. Instability studies on a spherical inertial electrostatic confinement

    Science.gov (United States)

    Kim, Hyung Jin

    The spherical inertial electrostatic confinement concept offers an alternative fusion plasma confinement scheme, where charged particles are accelerated and confined electrostatically with a series of biased spherical concentric electrodes. The inertia of the accelerated ions compresses the ions and builds up the space charge at the center of the cathode grid. The space charge of the ions attracts electrons which in turn accumulate a space charge. The accumulation of collective space charge creates a series of deep "virtual" electrostatic potential wells which confine and concentrate ions into a small volume where an appreciable number of nuclear fusion reactions could occur. It is very attractive for a power plant due to its mechanical simplicity and high power-to-mass ratio. However, its beam-plasma interactions are not clearly understood. In order to evaluate the inertial electrostatic confinement concept, it is essential to develop a reliable and flexible instability analysis method for an equilibrium plasma in a potential well. Subsequently stability of this well can be studied. As a part of this study, methods are sought to avoid or suppress any destructive instabilities. Methods to be explored include modification/control of the well profile, control of the electron to ion beam density ratio, control of the angular momentum of the beam, etc. For this purpose, a perturbative (deltaf) particle simulation techniques for a kinetic analysis is applied to simulate completely the dynamic evolution of perturbed Vlasov-Poisson equations and, in addition, to achieve much more accurate simulations of the nonlinear dynamics using less simulation particles compared to conventional particle-in-cell method. This model is used to study the behavior of two-stream-like instabilities related to the trapped spherically converging ions. Results show that steady-state solutions of the self-consistent Vlasov-Poisson equation in which angular momentum of positively charged particle

  20. A charged fusion product diagnostic for a spherical tokamak

    Science.gov (United States)

    Perez, Ramona Leticia Valenzuela

    Designs for future nuclear fusion power reactors rely on the ability to create a stable plasma (hot ionized gas of hydrogen isotopes) as a medium with which to sustain nuclear fusion reactions. My dissertation work involves designing, constructing, testing, installing, operating, and validating a new diagnostic for spherical tokamaks, a type of reactor test facility. Through detecting charged particles emitted from the plasma, this instrument can be used to study fusion reaction rates within the plasma and how they are affected by plasma perturbations. Quantitatively assessing nuclear fusion reaction rates at specific locations inside the plasma and as a function of time can provide valuable data that can be used to evaluate theory-based simulations related to energy transport and plasma stability. The Proton Detector (PD), installed in the Mega Amp Spherical Tokamak (MAST) at the Culham Centre for Fusion Energy (CCFE) in Abingdon, England, was the first instrument to experimentally detect 3 MeV Protons and 1 MeV Tritons created from deuterium- deuterium (hydrogen isotopes) nuclear fusion reactions inside a spherical tokamak's plasma. The PD consists of an array of particle detectors with a protective housing and the necessary signal conditioning electronics and readout. After several years of designing (which included simulations for detector orientations), fabricating, and testing the PD, it was installed in MAST and data were collected over a period of two months in the summer of 2013. Proton and triton rates as high as 200 kHz were measured and an initial radial profile of these fusion reaction rates inside the plasma was extracted. These results will be compared to a complementary instrument at MAST as well as theory-based simulations and form the knowledge basis for developing a larger future instrument. The design and performance of all instrument components (electrical, computational, mechanical), and subsequent data analysis methods and results are

  1. Thermo-mechanical screening tests to qualify beryllium pebble beds with non-spherical pebbles

    Energy Technology Data Exchange (ETDEWEB)

    Reimann, Joerg, E-mail: joerg.reimann@partner.kit.edu [IKET, Karlsruhe Institute of Technology, Karlsruhe (Germany); Fretz, Benjamin [KBHF GmbH, Eggenstein-Leopoldshafen (Germany); Pupeschi, Simone [IAM, Karlsruhe Institute of Technology, Karlsruhe (Germany)

    2015-10-15

    Highlights: • In present ceramic breeder blankets, pebble-shaped beryllium is used as a neutron multiplier. • Spherical pebbles are considered as the candidate material, however, non-spherical particles are of economic interest. • Thermo-mechanical pebble bed data do merely exist for non-spherical beryllium grades. • Uniaxial compression tests (UCTs), combined with the Hot Wire Technique (HWT) were used to measure the stress–strain relations and the thermal conductivity. • A small experimental set-up had to be used and a detailed 3D modelling was of prime importance. • Compared to spherical pebble beds, non-spherical pebble beds are generally softer and mainly the thermal conductivity is lower. - Abstract: In present ceramic breeder blankets, pebble-shaped beryllium is used as a neutron multiplier. Fairly spherical pebbles are considered as a candidate material, however, non-spherical particles are of economic interest because production costs are much lower. Yet, thermo-mechanical pebble bed data do merely exist for these beryllium grades, and the blanket relevant potential of these grades cannot be judged. Screening experiments were performed with three different grades of non-spherical beryllium pebbles, produced by different companies, accompanied by experiments with the reference beryllium pebble beds. Uniaxial compression tests (UCTs), combined with the Hot Wire Technique (HWT), were performed to measure both the stress–strain relation and the thermal conductivity, k, at different stress levels. Because of the limited amounts of the non-spherical materials, the experimental set-ups were small and a detailed 3D modelling was of prime importance in order to prove that the used design was appropriate. Compared to the pebble beds consisting of spherical pebbles, non-spherical pebble beds are generally softer (smaller stress for a given strain), and, mainly as a consequence of this, for a given strain value, the thermal conductivity is lower. This

  2. Finite-size scaling for the mean spherical model with inverse power law interaction

    Energy Technology Data Exchange (ETDEWEB)

    Brankov, J.G. (Joint Institute for Nuclear Research, Dubna (USSR))

    1989-08-01

    A new analytical technique based on integral transformations with Mittag-Leffler-type kernels is used to derive the finite-size scaling function for the free energy per particle of the mean spherical model with inverse power law asymptotics of the interaction potential. The asymptotic formation of the singularities in the specific heat and magnetic susceptibility at the bulk critical point is studied.

  3. PRODUCTION OF POROUS POWDER MATERIALS OF SPHERICAL POWDERS OF CORROSION-RESISTANT STEEL

    Directory of Open Access Journals (Sweden)

    V. N. Kovalevskij

    2012-01-01

    Full Text Available Production of porous powder materials from spherical powders of corrosion-resistant steel 12Х18н10Т with formation at low pressures 120–140 mpa in the mold with the subsequent activated sintering became possible due to increase of duration of process of spattering and formation of condensate particles (Si–C or (Mo–Si on surface.

  4. Impedance estimation of a finite absorber based on spherical array measurements

    DEFF Research Database (Denmark)

    Richard, Antoine Philippe André; Fernandez Grande, Efren; Brunskog, Jonas

    2016-01-01

    A method to characterize the surface impedance of materials is presented. The estimation is based on pressure measurements with a spherical microphone array. These measurements are used to reconstruct the sound pressure and particle velocity on the sample’s surface, from which the material’s impe...

  5. Effect of binder liquid type on spherical crystallization.

    Science.gov (United States)

    Maghsoodi, Maryam; Hajipour, Ali

    2014-11-01

    Spherical crystallization is a process of formation of agglomerates of crystals held together by binder liquid. This research focused on understanding the effect of type of solvents used as binder liquid on the agglomeration of crystals. Carbamazepine and ethanol/water were used respectively as a model drug and crystallization system. Eight solvents as binder liquid including chloroform, dichloromethane, isopropyl acetate, ethyl acetate, n-hexane, dimethyl aniline, benzene and toluene were examined to better understand the relationship between the physical properties of the binder liquid and its ability to bring about the formation of the agglomerates. Moreover, the agglomerates obtained from effective solvents as binder liquid were evaluated in term of size, apparent particle density and compressive strength. In this study the clear trend was observed experimentally in the agglomerate formation as a function of physical properties of the binder liquid such as miscibility with crystallization system. Furthermore, the properties of obtained agglomerates such as size, apparent particle density and compressive strength were directly related to physical properties of effective binder liquids. RESULTS of this study offer a useful starting point for a conceptual framework to guide the selection of solvent systems for spherical crystallization.

  6. Spherically symmetric inhomogeneous dust collapse in higher ...

    Indian Academy of Sciences (India)

    We consider a collapsing spherically symmetric inhomogeneous dust cloud in higher dimensional space-time. We show that the central singularity of collapse can be a strong curvature or a weak curvature naked singularity depending on the initial density distribution.

  7. Shape Evolution Synthesis of Monodisperse Spherical, Ellipsoidal, and Elongated Hematite (alpha-Fe2O3) Nanoparticles Using Ascorbic Acid

    NARCIS (Netherlands)

    Tan, W.F.; Yu, Y.T.; Wang, M.X.; Liu, F.; Koopal, L.K.

    2014-01-01

    Spherical, ellipsoidal, and elongated hematite particles have been obtained via a simple chemical precipitation reaction of FeCl3 and NaOH in the presence of ascorbic acid,(AA). The effects of pH, molar ratio of AA/Fe(III), and time on the formation and shape of the hematite particles were

  8. 3D Printing Electrically Small Spherical Antennas

    DEFF Research Database (Denmark)

    Kim, Oleksiy S.

    2013-01-01

    3D printing is applied for rapid prototyping of an electrically small spherical wire antenna. The model is first printed in plastic and subsequently covered with several layers of conductive paint. Measured results are in good agreement with simulations.......3D printing is applied for rapid prototyping of an electrically small spherical wire antenna. The model is first printed in plastic and subsequently covered with several layers of conductive paint. Measured results are in good agreement with simulations....

  9. Electrokinetic motion of a charged colloidal sphere in a spherical cavity with magnetic fields

    Science.gov (United States)

    Hsieh, Tzu H.; Keh, Huan J.

    2011-01-01

    The magnetohydrodynamic (MHD) effects on the translation and rotation of a charged colloidal sphere situated at the center of a spherical cavity filled with an arbitrary electrolyte solution when a constant magnetic field is imposed are analyzed at the quasisteady state. The electric double layers adjacent to the solid surfaces may have an arbitrary thickness relative to the particle and cavity radii. Through the use of a perturbation method to the leading order, the Stokes equations modified with the electric/Lorentz force term are dealt by using a generalized reciprocal theorem. Using the equilibrium double-layer potential distribution in the fluid phase from solving the linearized Poisson-Boltzmann equation, we obtain explicit formulas for the translational and angular velocities of the colloidal sphere produced by the MHD effects valid for all values of the particle-to-cavity size ratio. For the limiting case of an infinitely large cavity with an uncharged wall, our result reduces to the relevant solution for an unbounded spherical particle available in the literature. The boundary effect on the MHD motion of the spherical particle is a qualitatively and quantitatively sensible function of the parameters a/b and κa, where a and b are the radii of the particle and cavity, respectively, and κ is the reciprocal of the Debye screening length. In general, the proximity of the cavity wall reduces the MHD migration but intensifies the MHD rotation of the particle.

  10. Spherical cows in dark matter indirect detection

    Science.gov (United States)

    Bernal, Nicolás; Necib, Lina; Slatyer, Tracy R.

    2016-12-01

    Dark matter (DM) halos have long been known to be triaxial, but in studies of possible annihilation and decay signals they are often treated as approximately spherical. In this work, we examine the asymmetry of potential indirect detection signals of DM annihilation and decay, exploiting the large statistics of the hydrodynamic simulation Illustris. We carefully investigate the effects of the baryons on the sphericity of annihilation and decay signals for both the case where the observer is at 8.5 kpc from the center of the halo (exemplified in the case of Milky Way-like halos), and for an observer situated well outside the halo. In the case of Galactic signals, we find that both annihilation and decay signals are expected to be quite symmetric, with axis ratios very different from 1 occurring rarely. In the case of extragalactic signals, while decay signals are still preferentially spherical, the axis ratio for annihilation signals has a much flatter distribution, with elongated profiles appearing frequently. Many of these elongated profiles are due to large subhalos and/or recent mergers. Comparing to gamma-ray emission from the Milky Way and X-ray maps of clusters, we find that the gamma-ray background appears less spherical/more elongated than the expected DM signal from the large majority of halos, and the Galactic gamma ray excess appears very spherical, while the X-ray data would be difficult to distinguish from a DM signal by elongation/sphericity measurements alone.

  11. Accurate particle speed prediction by improved particle speed measurement and 3-dimensional particle size and shape characterization technique

    DEFF Research Database (Denmark)

    Cernuschi, Federico; Rothleitner, Christian; Clausen, Sønnik

    2017-01-01

    methods, e.g. laser light scattering, and velocity by the double disk (DD) method. In this article we present two novel techniques, which allow a more accurate measurement of mass, velocity and shape, and we later compare the experimentally obtained flow velocities of particles with a simulation that also...... includes the particle's shape parameter, known as sphericity. Mass and sphericity are obtained from 3-dimensional data with an industrial X-ray computed tomography (CT) scanner. CT data can be used to accurately determine the volume-basis median of the particles (using the volume-equivalent particle......Accurate particle mass and velocity measurement is needed for interpreting test results in erosion tests of materials and coatings. The impact and damage of a surface is influenced by the kinetic energy of a particle, i.e. particle mass and velocity. Particle mass is usually determined with optical...

  12. The attachment of colloidal particles to environmentally relevant surfaces and the effect of particle shape.

    Science.gov (United States)

    McNew, Coy P; Kananizadeh, Negin; Li, Yusong; LeBoeuf, Eugene J

    2017-02-01

    Despite the prevalence of nonspherical colloidal particles, the role of particle shape in the transport of colloids is largely understudied. This study investigates the attachment of colloidal particles onto environmentally relevant surfaces while varying particle shape and ionic strength. Using quartz crystal microbalance and atomic force microscopy measurements, the role of particle shape was elucidated and possible mechanisms discussed. The attachment of both spherical and stretched polystyrene colloidal particles onto a smooth alginate-coated silica surface showed qualitative agreement with DLVO theory. Attachment onto a Harpeth humic acid (HHA) surface, however, significantly deviated from DLVO theory due to its high surface heterogeneity and extended confirmation from the silica surface. This extended confirmation provided increased potential for spherical particle entanglement, while the enlarged major axis of the stretched particles hindered their ability to attach. As ionic strength increased, the HHA layer condensed and provided less potential for spherical particle entanglement and therefore the selectivity for spherical particle attachment vanished. The findings presented in this study suggest that colloidal particle shape may play a complex and important role in predicting the transport of colloidal particles, especially in the presence of natural organic matter-coated surfaces. Copyright © 2016 Elsevier Ltd. All rights reserved.

  13. On the submerging of a spherical intruder into granular beds

    Science.gov (United States)

    Wu, Chuan-Yu; Zhang, Ling; Chen, Lan

    2017-06-01

    Granular materials are complex systems and their mechanical behaviours are determined by the material properties of individual particles, the interaction between particles and the surrounding media, which are still incompletely understood. Using an advanced discrete element method (DEM), we simulate the submerging process of a spherical projectile (an intruder) into granular materials of various properties with a zero penetration velocity (i.e. the intruder is touching the top surface of the granular bed and released from stationary) and examine its settling behaviour. By systematically changing the density and size of the intruder and the particle density (i.e. the density of the particles in the granular bed), we find that the intruder can sink deep into the granular bed even with a zero penetration velocity. Furthermore, we confirm that under certain conditions the granular bed can behave like a Newtonian liquid and the submerging intruder can reach a constant velocity, i.e. the terminal velocity, identical to the settling of a sphere in a liquid, as observed experimentally. A mathematical model is also developed to predict the maximum penetration depth of the intruder. The model predictions are compared with experimental data reported in the literature,good agreement was obtained, demonstrating the model can accurately predict the submerging behaviour of the intruder in the granular media.

  14. On the submerging of a spherical intruder into granular beds

    Directory of Open Access Journals (Sweden)

    Wu Chuan-Yu

    2017-01-01

    Full Text Available Granular materials are complex systems and their mechanical behaviours are determined by the material properties of individual particles, the interaction between particles and the surrounding media, which are still incompletely understood. Using an advanced discrete element method (DEM, we simulate the submerging process of a spherical projectile (an intruder into granular materials of various properties with a zero penetration velocity (i.e. the intruder is touching the top surface of the granular bed and released from stationary and examine its settling behaviour. By systematically changing the density and size of the intruder and the particle density (i.e. the density of the particles in the granular bed, we find that the intruder can sink deep into the granular bed even with a zero penetration velocity. Furthermore, we confirm that under certain conditions the granular bed can behave like a Newtonian liquid and the submerging intruder can reach a constant velocity, i.e. the terminal velocity, identical to the settling of a sphere in a liquid, as observed experimentally. A mathematical model is also developed to predict the maximum penetration depth of the intruder. The model predictions are compared with experimental data reported in the literature,good agreement was obtained, demonstrating the model can accurately predict the submerging behaviour of the intruder in the granular media.

  15. Detection of Bioaerosols using Single Particle Thermal Emission Spectroscopy

    Science.gov (United States)

    2013-03-01

    Distribution List 21 iv List of Figures Figure 1. Plot of the characteristic cooling period, τ (sec), for a spherical glycerin particle...the surrounding gas. To get an idea of the magnitude for the possible values of τ, we consider a glycerin particle of varying diameters, with the...4 Figure 1. Plot of the characteristic cooling period, τ (sec), for a spherical glycerin particle heated to some initial temperature Tp

  16. Toward automated analysis of particle holograms

    Science.gov (United States)

    Caulfield, H. J.

    1987-01-01

    A preliminary study of approaches for extracting and analyzing data from particle holograms is discussed. It concludes that: (1) for thin spherical particles, out-of-focus methods are optimum; (2) for thin nonspherical particles, out-of-focus methods are useful but must be supplemented by in-focus methods; (3) a complex method of projection and back projection can remove out-of-focus data for deep particles.

  17. Models of spherical shells as sources of Majumdar-Papapetrou type spacetimes

    CERN Document Server

    García-Reyes, Gonzalo

    2016-01-01

    By starting with a seed Newtonian potential-density pair we construct relativistic thick spherical shell models for a Majumdar-Papapetrou type conformastatic spacetime. As simple example, we considerer a family of Plummer type relativistic spherical shells. These objects are then used to model a system composite by a dust disk and a halo of matter. We study the equatorial circular motion of test particles around the structures. Also the stability of the orbits is analyzed for radial perturbation using an extension of the Rayleigh criterion. The models considered satisfying all the energy conditions.

  18. Nanomanufacturing of Tobacco Mosaic Virus-Based Spherical Biomaterials Using a Continuous Flow Method.

    Science.gov (United States)

    Bruckman, Michael A; VanMeter, Allen; Steinmetz, Nicole F

    2015-01-12

    Nanomanufacturing of nanoparticles is critical for potential translation and commercialization. Continuous flow devices can alleviate this need through unceasing production of nanoparticles. Here we demonstrate the scaled-up production of spherical nanoparticles functionalized with biomedical cargos from the rod-shaped plant virus tobacco mosaic virus (TMV) using a mesofluidic, continued flow method. Production yields were increased 30-fold comparing the mesofluidic device versus batch methods. Finally, we produced MRI contrast agents of select sizes, with per particle relaxivity reaching 979,218 mM(-1) s(-1) at 60 MHz. These TMV-based spherical nanoparticle MRI contrast agents are in the top echelon of relaxivity per nanoparticle.

  19. Generalized theory of resonance scattering (GTRS) using the translational addition theorem for spherical wave functions.

    Science.gov (United States)

    Mitri, Farid

    2014-11-01

    The generalized theory of resonance scattering (GTRS) by an elastic spherical target in acoustics is extended to describe the arbitrary scattering of a finite beam using the addition theorem for the spherical wave functions of the first kind under a translation of the coordinate origin. The advantage of the proposed method over the standard discrete spherical harmonics transform previously used in the GTRS formalism is the computation of the off-axial beam-shape coefficients (BSCs) stemming from a closed-form partial-wave series expansion representing the axial BSCs in spherical coordinates. With this general method, the arbitrary acoustical scattering can be evaluated for any particle shape and size, whether the particle is partially or completely illuminated by the incident beam. Numerical examples for the axial and off-axial resonance scattering from an elastic sphere placed arbitrarily in the field of a finite circular piston transducer with uniform vibration are provided. Moreover, the 3-D resonance directivity patterns illustrate the theory and reveal some properties of the scattering. Numerous applications involving the scattering phenomenon in imaging, particle manipulation, and the characterization of multiphase flows can benefit from the present analysis because all physically realizable beams radiate acoustical waves from finite transducers as opposed to waves of infinite extent.

  20. Recent Progress on Spherical Torus Research

    Energy Technology Data Exchange (ETDEWEB)

    Ono, Masayuki [PPPL; Kaita, Robert [PPPL

    2014-01-01

    The spherical torus or spherical tokamak (ST) is a member of the tokamak family with its aspect ratio (A = R0/a) reduced to A ~ 1.5, well below the normal tokamak operating range of A ≥ 2.5. As the aspect ratio is reduced, the ideal tokamak beta β (radio of plasma to magnetic pressure) stability limit increases rapidly, approximately as β ~ 1/A. The plasma current it can sustain for a given edge safety factor q-95 also increases rapidly. Because of the above, as well as the natural elongation κ, which makes its plasma shape appear spherical, the ST configuration can yield exceptionally high tokamak performance in a compact geometry. Due to its compactness and high performance, the ST configuration has various near term applications, including a compact fusion neutron source with low tritium consumption, in addition to its longer term goal of attractive fusion energy power source. Since the start of the two megaampere class ST facilities in 2000, National Spherical Torus Experiment (NSTX) in the US and Mega Ampere Spherical Tokamak (MAST) in UK, active ST research has been conducted worldwide. More than sixteen ST research facilities operating during this period have achieved remarkable advances in all of fusion science areas, involving fundamental fusion energy science as well as innovation. These results suggest exciting future prospects for ST research both near term and longer term. The present paper reviews the scientific progress made by the worldwide ST research community during this new mega-ampere-ST era.

  1. Scaling of a fast spherical discharge

    Energy Technology Data Exchange (ETDEWEB)

    Antsiferov, P. S., E-mail: Ants@isan.troitsk.ru; Dorokhin, L. A. [Russian Academy of Sciences, Institute of Spectroscopy (Russian Federation)

    2017-02-15

    The influence of the discharge cavity dimensions on the properties of the spherical plasma formed in a fast discharge was studied experimentally. The passage of a current pulse with an amplitude of 30–40 kA and a rise rate of ~10{sup 12} A/s (a fast discharge) through a spherical ceramic (Al{sub 2}O{sub 3}) cavity with an inner diameter of 11 mm filled with argon at a pressure of 80 Pa results in the formation of a 1- to 2-mm-diameter spherical plasma with an electron temperature of several tens of electronvolts and a density of 10{sup 18}–10{sup 19} cm{sup –3}. It is shown that an increase in the inner diameter of the discharge cavity from 11 to 21 mm leads to the fourfold increase in the formation time of the spherical plasma and a decrease in the average ion charge. A decrease in the cavity diameter to 7 mm makes the spherical plasma unstable.

  2. Spherical angular spectrum and the fractional order Fourier transform.

    Science.gov (United States)

    Pellat-Finet, Pierre; Durand, Pierre-Emmanuel; Fogret, Eric

    2006-12-01

    The notion of a spherical angular spectrum leads to the decomposition of the field amplitude on a spherical emitter into a sum of spherical waves that converge onto the Fourier sphere of the emitter. Unlike the usual angular spectrum, the spherical angular spectrum is propagated as the field amplitude, in a way that can be expressed by a fractional order Fourier transform.

  3. The effects of particle shape and size on T2 relaxation in magnetic resonance imaging.

    Science.gov (United States)

    York, Joseph N; Albanese, Christopher; Rodriguez, Olga; Le, Yi-Chien; Ackun-Farmmer, Marian; Van Keuren, Edward

    2014-11-01

    Superparamagnetic iron oxide nanoparticles have recently been developed as T2 contrast agents for magnetic resonance imaging. Here we report the dependence of the phase relaxivity, r2, on the particle shape. We show that the size dependence of the relaxivity for spherical particles can be generalized to spheroidal particles. In addition, we show that the saturation of relaxivity above a certain size observed in spherical particles does not occur in the spheroidal particles investigated.

  4. Spherical agglomerates of pure drug nanoparticles for improved pulmonary delivery in dry powder inhalers

    Science.gov (United States)

    Hu, Jun; Dong, Yuancai; Pastorin, Giorgia; Ng, Wai Kiong; Tan, Reginald B. H.

    2013-04-01

    The aim of this study was to produce micron-sized spherical agglomerates of pure drug nanoparticles to achieve improved aerosol performance in dry powder inhalers (DPIs). Sodium cromoglicate was chosen as the model drug. Pure drug nanoparticles were prepared through a bottom-up particle formation process, liquid antisolvent precipitation, and then rapidly agglomerated into porous spherical microparticles by immediate (on-line) spray drying. Nonporous spherical drug microparticles with similar geometric size distribution were prepared by conventional spray drying of the aqueous drug solution, which together with the mechanically micronized drug particles were used as the control samples. The three samples were characterized by field emission scanning electron microscopy, laser diffraction, Brunauer-Emmett-Teller analysis, density measurement, powder X-ray diffraction, and in vitro aerosol deposition measurement with a multistage liquid impinger. It was found that drug nanoparticles with a diameter of 100 nm were precipitated and agglomerated into highly porous spherical microparticles with a volume median diameter ( D 50 %) of 2.25 ± 0.08 μm and a specific surface area of 158.63 ± 3.27 m2/g. In vitro aerosol deposition studies showed the fine particle fraction of such spherical agglomerates of drug nanoparticles was increased by more than 50 % in comparison with the control samples, demonstrating significant improvements in aerosol performance. The results of this study indicated the potential of the combined particle engineering process of liquid antisolvent precipitation followed by immediate (on-line) spray drying in the development of novel DPI drug products with improved aerosol performance.

  5. Background reduction of a spherical gaseous detector

    Energy Technology Data Exchange (ETDEWEB)

    Fard, Ali Dastgheibi [Laboratoire Souterrain de Modane, France ali.dastgheibi-fard@lsm.in2p3.fr (France); Loaiza, Pia; Piquemal, Fabrice [Laboratoire Souterrain de Modane (France); Giomataris, Ioannis; Gray, David; Gros, Michel; Magnier, Patrick; Navick, Xavier-François [CEA Saclay - IRFU/SEDI - 91191 Gif sur Yvette (France); Savvidis, Ilias [Aristotle University of Thessaloniki (Greece)

    2015-08-17

    The Spherical gaseous detector (or Spherical Proportional Counter, SPC) is a novel type of detector. It consists of a large spherical volume filled with gas, using a single detection readout channel. The detector allows 100 % detection efficiency. SEDINE is a low background version of SPC installed at the Laboratoire Souterrain de Modane (LSM) underground laboratory (4800 m.w.e) looking for rare events at very low energy threshold, below 100 eV. This work presents the details on the chemical cleaning to reduce internal {sup 210}Pb surface contamination on the copper vessel and the external radon reduction achieved via circulation of pure air inside anti-radon tent. It will be also show the radon measurement of pure gases (Ar, N, Ne, etc) which are used in the underground laboratory for the low background experiments.

  6. Lévy particles

    DEFF Research Database (Denmark)

    Hansen, Linda Vadgård; Thorarinsdottir, Thordis Linda; Gneiting, Tilmann

    Lévy particles provide a flexible framework for modelling and simulating threedimensional star-shaped random sets. The radial function of a Lévy particle arises from a kernel smoothing of a Lévy basis, and is associated with an isotropic random field on the sphere. If the kernel is proportional...... to a von Mises–Fisher density, or uniform on a spherical cap, the correlation function of the associated random field admits a closed form expression. Using a Gaussian basis, the fractal or Hausdorff dimension of the surface of the Lévy particle reflects the decay of the correlation function at the origin......, as quantified by the fractal index. Under power kernels we obtain particles with boundaries of any Hausdorff dimension between 2 and 3....

  7. POLARON IN CYLINDRICAL AND SPHERICAL QUANTUM DOTS

    Directory of Open Access Journals (Sweden)

    L.C.Fai

    2004-01-01

    Full Text Available Polaron states in cylindrical and spherical quantum dots with parabolic confinement potentials are investigated applying the Feynman variational principle. It is observed that for both kinds of quantum dots the polaron energy and mass increase with the increase of Frohlich electron-phonon coupling constant and confinement frequency. In the case of a spherical quantum dot, the polaron energy for the strong coupling is found to be greater than that of a cylindrical quantum dot. The energy and mass are found to be monotonically increasing functions of the coupling constant and the confinement frequency.

  8. Shape Effect on Particle-Lipid Bilayer Membrane Association, Cellular Uptake, and Cytotoxicity.

    Science.gov (United States)

    Tree-Udom, Thapakorn; Seemork, Jiraporn; Shigyou, Kazuki; Hamada, Tsutomu; Sangphech, Naunpun; Palaga, Tanapat; Insin, Numpon; Pan-In, Porntip; Wanichwecharungruang, Supason

    2015-11-04

    Although computer simulation and cell culture experiments have shown that elongated spherical particles can be taken up into cells more efficiently than spherical particles, experimental investigation on effects of these different shapes over the particle-membrane association has never been reported. Therefore, whether the higher cellular uptake of an elongated spherical particles is a result of a better particle-membrane association as suggested by some calculation works or a consequence of its influence on other cellular trans-membrane components involved in particle translocation process, cannot be concluded. Here, we study the effect of particle shape on the particle-membrane interaction by monitoring the association between particles of various shapes and lipid bilayer membrane of artificial cell-sized liposomes. Among the three shaped lanthanide-doped NaYF4 particles, all with high shape purity and uniformity, similar crystal phase, and surface chemistry, the elongated spherical particle shows the highest level of membrane association, followed by the spherical particle with a similar radius, and the hexagonal prism-shaped particle, respectively. The free energy of membrane curvature calculated based on a membrane indentation induced by a particle association indicates that among the three particle shapes, the elongated spherical particle give the most stable membrane curvature. The elongated spherical particles show the highest cellular uptake into cytosol of human melanoma (A-375) and human liver carcinoma (HepG2) cells when observed through a confocal laser scanning fluorescence microscope. Quantitative study using flow cytometry also gives the same result. The elongated spherical particles also possess the highest cytotoxicity in A-375 and normal skin (WI-38) cell lines, comparing to the other two shaped particles.

  9. Controlled drug release on amine functionalized spherical MCM-41

    Energy Technology Data Exchange (ETDEWEB)

    Szegedi, Agnes, E-mail: szegedi@chemres.hu [Institute of Materials and Environmental Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, 1025 Budapest, Pusztaszeri ut 59-67 (Hungary); Popova, Margarita; Goshev, Ivan [Institute of Organic Chemistry with Centre of Phytochemistry, Bulgarian Academy of Sciences, Sofia (Bulgaria); Klebert, Szilvia [Institute of Materials and Environmental Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, 1025 Budapest, Pusztaszeri ut 59-67 (Hungary); Mihaly, Judit [Institute of Molecular Pharmacology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, 1025 Budapest, Pusztaszeri ut 59-67 (Hungary)

    2012-10-15

    MCM-41 silica with spherical morphology and small particle sizes (100 nm) was synthesized and modified by post-synthesis method with different amounts of 3-aminopropyltriethoxysilane (APTES). A comparative study of the adsorption and release of a model drug, ibuprofen, was carried out. The modified and drug loaded mesoporous materials were characterized by XRD, TEM, N{sub 2} physisorption, elemental analysis, thermal analysis and FT-IR spectroscopy. A new method was developed for the quantitative determination of amino groups in surface modified mesoporous materials by the ninhydrin reaction. Good correlation was found between the amino content of the MCM-41 materials determined by the ninhydrin method and their ibuprofen adsorption capacity. Amino modification resulted in high degree of ibuprofen loading and slow release rate in comparison to the parent non-modified MCM-41. - Graphical abstract: Determination of surface amino groups by ninhidrin method. Highlights: Black-Right-Pointing-Pointer Spherical MCM-41 modified by different amounts of APTES was studied. Black-Right-Pointing-Pointer Ibuprofen (IBU) adsorption and release characteristics was tested. Black-Right-Pointing-Pointer The ninhydrin reaction was used for the quantitative determination of amino groups. Black-Right-Pointing-Pointer Stoichiometric amount of APTES is enough for totally covering the surface with amino groups. Black-Right-Pointing-Pointer Good correlation was found between the amino content and IBU adsorption capacity.

  10. Divertor Heat Flux Mitigation in the National Spherical Torus Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Soukhanovskii, V A; Maingi, R; Gates, D A; Menard, J E; Paul, S F; Raman, R; Roquemore, A L; Bell, M G; Bell, R E; Boedo, J A; Bush, C E; Kaita, R; Kugel, H W; LeBlanc, B P; Mueller, D

    2008-08-04

    Steady-state handling of divertor heat flux is a critical issue for both ITER and spherical torus-based devices with compact high power density divertors. Significant reduction of heat flux to the divertor plate has been achieved simultaneously with favorable core and pedestal confinement and stability properties in a highly-shaped lower single null configuration in the National Spherical Torus Experiment (NSTX) [M. Ono et al., Nucl. Fusion 40, 557 2000] using high magnetic flux expansion at the divertor strike point and the radiative divertor technique. A partial detachment of the outer strike point was achieved with divertor deuterium injection leading to peak flux reduction from 4-6 MW m{sup -2} to 0.5-2 MW m{sup -2} in small-ELM 0.8-1.0 MA, 4-6 MW neutral beam injection-heated H-mode discharges. A self-consistent picture of outer strike point partial detachment was evident from divertor heat flux profiles and recombination, particle flux and neutral pressure measurements. Analytic scrape-off layer parallel transport models were used for interpretation of NSTX detachment experiments. The modeling showed that the observed peak heat flux reduction and detachment are possible with high radiated power and momentum loss fractions, achievable with divertor gas injection, and nearly impossible to achieve with main electron density, divertor neutral density or recombination increases alone.

  11. New generation nuclear fuel structures: dense particles in selectively soluble matrix

    Energy Technology Data Exchange (ETDEWEB)

    Sickafus, Kurt E [Los Alamos National Laboratory; Devlin, David J [Los Alamos National Laboratory; Jarvinen, Gordon D [Los Alamos National Laboratory; Patterson, Brian M [Los Alamos National Laboratory; Pattillo, Steve G [Los Alamos National Laboratory; Valdez, James [Los Alamos National Laboratory; Phillips, Jonathan [Los Alamos National Laboratory

    2009-01-01

    We have developed a technology for dispersing sub-millimeter sized fuel particles within a bulk matrix that can be selectively dissolved. This may enable the generation of advanced nuclear fuels with easy separation of actinides and fission products. The large kinetic energy of the fission products results in most of them escaping from the sub-millimeter sized fuel particles and depositing in the matrix during burning of the fuel in the reactor. After the fuel is used and allowed to cool for a period of time, the matrix can be dissolved and the fission products removed for disposal while the fuel particles are collected by filtration for recycle. The success of such an approach would meet a major goal of the GNEP program to provide advanced recycle technology for nuclear energy production. The benefits of such an approach include (1) greatly reduced cost of the actinide/fission product separation process, (2) ease of recycle of the fuel particles, and (3) a radiation barrier to prevent theft or diversion of the recycled fuel particles during the time they are re-fabricated into new fuel. In this study we describe a method to make surrogate nuclear fuels of micrometer scale W (shell)/Mo (core) or HfO2 particles embedded in an MgO matrix that allows easy separation of the fission products and their embedded particles. In brief, the method consists of physically mixing W-Mo or hafnia particles with an MgO precursor. Heating the mixture, in air or argon, without agitation, to a temperature is required for complete decomposition of the precursor. The resulting material was examined using chemical analysis, scanning electron microscopy, X-ray diffraction and micro X-ray computed tomography and found to consist of evenly dispersed particles in an MgO + matrix. We believe this methodology can be extended to actinides and other matrix materials.

  12. Electric Double Layer electrostatics of spherical polyelectrolyte brushes with pH-dependent charge density

    Science.gov (United States)

    Li, Hao; Chen, Guang; Sinha, Shayandev; Das, Siddhartha; Soft Matter, Interfaces,; Energy Laboratory (Smiel) Team

    Understanding the electric double layer (EDL) electrostatics of spherical polyelectrolyte (PE) brushes, which are spherical particles grafted with PE layers, is essential for appropriate use of PE-grfated micro-nanoparticles for targeted drug delivery, oil recovery, water harvesting, emulsion stabilization, emulsion breaking, etc. Here we elucidate the EDL electrostatics of spherical PE brushes for the case where the PE exhibits pH-dependent charge density. This pH-dependence necessitates the consideration of explicit hydrogen ion concentration, which in turn dictates the distribution of monomers along the length of the grafted PE. This monomer distribution is shown to be a function of the nature of the sphere (metallic or a charged or uncharged dielectric or a liquid-filled sphere). All the calculations are performed for the case where the PE electrostatics can be decoupled from the PE elastic and excluded volume effects. Initial predictions are also provided for the case where such decoupling is not possible.

  13. Calibration of optical particle-size analyzer

    Science.gov (United States)

    Pechin, William H.; Thacker, Louis H.; Turner, Lloyd J.

    1979-01-01

    This invention relates to a system for the calibration of an optical particle-size analyzer of the light-intercepting type for spherical particles, wherein a rotary wheel or disc is provided with radially-extending wires of differing diameters, each wire corresponding to a particular equivalent spherical particle diameter. These wires are passed at an appropriate frequency between the light source and the light detector of the analyzer. The reduction of light as received at the detector is a measure of the size of the wire, and the electronic signal may then be adjusted to provide the desired signal for corresponding spherical particles. This calibrator may be operated at any time without interrupting other processing.

  14. Alpha Anisotropy Studies of Near-Spherical and Deformed Nuclei

    CERN Multimedia

    Van Duppen, P

    2002-01-01

    % IS329 \\\\ \\\\ Although it was the first decay mode to be discovered, the process of $\\alpha$-particle emission is still poorly understood. A few years ago the first systematic study of anisotropic $\\alpha$-decay triggered renewed theoretical interest. Nevertheless, today the theories are still not adequate enough and more experimental data are urgently needed. We therefore measure the $\\alpha$-anisotropies of the favoured transitions of a number of near-spherical Rn and At isotopes, and of deformed nuclei near A=220. As the different models yield contradictory predictions for the transitions that are investigated, the measurements will allow to discern on their validity. They will at the same time provide the necessary basis for further theoretical developments.

  15. Penetration of spherical projectiles into wet granular media.

    Science.gov (United States)

    Birch, S P D; Manga, M; Delbridge, B; Chamberlain, M

    2014-09-01

    We measure experimentally the penetration depth d of spherical particles into a water-saturated granular medium made of much smaller sand-sized grains. We vary the density, size R, and velocity U of the impacting spheres, and the size δ of the grains in the granular medium. We consider velocities between 7 and 107 m/s, a range not previously addressed, but relevant for impacts produced by volcanic eruptions. We find that d∝R(1/3)δ(1/3)U(2/3). The scaling with velocity is similar to that identified in previous, low-velocity collisions, but it also depends on the size of the grains in the granular medium. We develop a model, consistent with the observed scaling, in which the energy dissipation is dominated by the work required to rearrange grains along a network of force chains in the granular medium.

  16. Controlled drug release on amine functionalized spherical MCM-41

    Science.gov (United States)

    Szegedi, Agnes; Popova, Margarita; Goshev, Ivan; Klébert, Szilvia; Mihály, Judit

    2012-10-01

    MCM-41 silica with spherical morphology and small particle sizes (100 nm) was synthesized and modified by post-synthesis method with different amounts of 3-aminopropyltriethoxysilane (APTES). A comparative study of the adsorption and release of a model drug, ibuprofen, was carried out. The modified and drug loaded mesoporous materials were characterized by XRD, TEM, N2 physisorption, elemental analysis, thermal analysis and FT-IR spectroscopy. A new method was developed for the quantitative determination of amino groups in surface modified mesoporous materials by the ninhydrin reaction. Good correlation was found between the amino content of the MCM-41 materials determined by the ninhydrin method and their ibuprofen adsorption capacity. Amino modification resulted in high degree of ibuprofen loading and slow release rate in comparison to the parent non-modified MCM-41.

  17. Modeling multipole dielectric spherical nanoantenna for optical and THz range

    Science.gov (United States)

    Storozhenko, Dmitry; Dzyuba, Vladimir; Kulchin, Yuri

    2017-09-01

    The paper gives the result of a numerical calculation of the Maxwell equation by the finite element method for a dielectric particle of spherical shape in the optical and THz ranges with a size 0.375÷0.75 of wavelength. The nature of the electric field distribution inside the sphere is shown in the case of high-order resonance for the optical range. The idea was put forward to use the resonance feature of the dielectric sphere to amplify the current in the conductor whip antenna. It is shown, that the use of such an antenna makes it possible to achieve amplification in the conductor up to 30 dB.

  18. Self-similar spherical metrics with tangential pressure

    CERN Document Server

    Gair, J R

    2002-01-01

    A family of spherically symmetric spacetimes is discussed, which have anisotropic pressure and possess a homothetic Killing vector. The spacetimes are composed of dust with a tangential pressure provided by angular momentum of the dust particles. The solution is given implicitly by an elliptic integral and depends on four arbitrary functions. These represent the initial configurations of angular momentum, mass, energy and position of the shells. The solution is derived by imposing self-similarity in the coordinates R, the shell label, and tau, the proper time experienced by the dust. Conditions for evolution without shell crossing and a description of singularity formation are given and types of solution discussed. General properties of the solutions are illustrated by reference to a particular case, which represents a universe that exists for an infinite time, but in which every shell expands and recollapses in a finite time.

  19. Micro-tearing modes in the Mega Ampere Spherical Tokamak

    CERN Document Server

    Applegate, D J; Connor, J W; Cowley, S C; Dorland, W; Hastie, R J; Joiner, N; 10.1088/0741-3335/49/8/001

    2011-01-01

    Recent gyrokinetic stability calculations have revealed that the spherical tokamak is susceptible to tearing parity instabilities with length scales of a few ion Larmor radii perpendicular to the magnetic field lines. Here we investigate this 'micro-tearing' mode in greater detail to uncover its key characteristics, and compare it with existing theoretical models of the phenomenon. This has been accomplished using a full numerical solution of the linear gyrokinetic-Maxwell equations. Importantly, the instability is found to be driven by the free energy in the electron temperature gradient as described in the literature. However, our calculations suggest it is not substantially affected by either of the destabilising mechanisms proposed in previous theoretical models. Instead the instability is destabilised by interactions with magnetic drifts, and the electrostatic potential. Further calculations reveal that the mode is not significantly destabilised by the flux surface shaping or the large trapped particle f...

  20. Spherical Horn Array for Wideband Propagation Measurements

    DEFF Research Database (Denmark)

    Franek, Ondrej; Pedersen, Gert Frølund

    2011-01-01

    A spherical array of horn antennas designed to obtain directional channel information and characteristics is introduced. A dual-polarized quad-ridged horn antenna with open flared boundaries and coaxial feeding for the frequency band 600 MHz–6 GHz is used as the element of the array. Matching...... for a wideband multipath propagation studies....

  1. Exact solutions of the spherically symmetric multidimensional ...

    African Journals Online (AJOL)

    The complete orthonormalised energy eigenfunctions and the energy eigenvalues of the spherically symmetric isotropic harmonic oscillator in N dimensions, are obtained through the methods of separation of variables. Also, the degeneracy of the energy levels are examined. KEY WORDS: - Schrödinger Equation, Isotropic ...

  2. Spherical projections and liftings in geometric tomography

    DEFF Research Database (Denmark)

    Goodey, Paul; Kiderlen, Markus; Weil, Wolfgang

    2011-01-01

    We consider a variety of integral transforms arising in Geometric Tomography. It will be shown that these can be put into a common framework using spherical projection and lifting operators. These operators will be applied to support functions and surface area measures of convex bodies and to rad...

  3. Noncommutative spherically symmetric spacetimes at semiclassical order

    Science.gov (United States)

    Fritz, Christopher; Majid, Shahn

    2017-07-01

    Working within the recent formalism of Poisson-Riemannian geometry, we completely solve the case of generic spherically symmetric metric and spherically symmetric Poisson-bracket to find a unique answer for the quantum differential calculus, quantum metric and quantum Levi-Civita connection at semiclassical order O(λ) . Here λ is the deformation parameter, plausibly the Planck scale. We find that r, t, d r, d t are all forced to be central, i.e. undeformed at order λ, while for each value of r, t we are forced to have a fuzzy sphere of radius r with a unique differential calculus which is necessarily nonassociative at order λ2 . We give the spherically symmetric quantisation of the FLRW cosmology in detail and also recover a previous analysis for the Schwarzschild black hole, now showing that the quantum Ricci tensor for the latter vanishes at order λ. The quantum Laplace-Beltrami operator for spherically symmetric models turns out to be undeformed at order λ while more generally in Poisson-Riemannian geometry we show that it deforms to □f+λ2ωαβ(Ricγα-Sγα)(∇^βdf)γ+O(λ2) in terms of the classical Levi-Civita connection \\widehat\

  4. Spherical Tolman-Bondi Models in Cosmology

    Science.gov (United States)

    Bochicchio, I.; Laserra, E.

    2010-09-01

    Spherical symmetry is considered and exact solutions of Tolman-Bondi equations are studied taking advantage from Ricci principal curvature depending on the radial coordinate. Moreover an expansion of the exact solutions in fractional Puiseux series in considered to compare Euclidean and not Euclidean cases.

  5. Determining a Sonographic Nomogram for Gallbladder Spherical ...

    African Journals Online (AJOL)

    Kurtosis and skewness values (0.991 and 0.152 respectively) showed even distribution . This study establishes a normogram for the population using the model formula and could be used in the assessment of gallbladder in conditions giving rise to gallbladder hydrops. Keywords: Sonography, Gallbladder Spherical index, ...

  6. A Generalization of the Spherical Inversion

    Science.gov (United States)

    Ramírez, José L.; Rubiano, Gustavo N.

    2017-01-01

    In the present article, we introduce a generalization of the spherical inversion. In particular, we define an inversion with respect to an ellipsoid, and prove several properties of this new transformation. The inversion in an ellipsoid is the generalization of the elliptic inversion to the three-dimensional space. We also study the inverse images…

  7. Spherically symmetric inhomogeneous dust collapse in higher ...

    Indian Academy of Sciences (India)

    Higher dimensional space-time; naked singularity; cosmic censorship. PACS Nos 04.20.Dw; 04.50. ... The existence of strong curvature naked singularities in gravitational collapse of spherically symmetric space-times ..... distributions (in an appropriate metric space) can be discussed along the lines of [16]. 3. Strength of the ...

  8. Spherical hashing: binary code embedding with hyperspheres.

    Science.gov (United States)

    Heo, Jae-Pil; Lee, Youngwoon; He, Junfeng; Chang, Shih-Fu; Yoon, Sung-Eui

    2015-11-01

    Many binary code embedding schemes have been actively studied recently, since they can provide efficient similarity search, and compact data representations suitable for handling large scale image databases. Existing binary code embedding techniques encode high-dimensional data by using hyperplane-based hashing functions. In this paper we propose a novel hypersphere-based hashing function, spherical hashing, to map more spatially coherent data points into a binary code compared to hyperplane-based hashing functions. We also propose a new binary code distance function, spherical Hamming distance, tailored for our hypersphere-based binary coding scheme, and design an efficient iterative optimization process to achieve both balanced partitioning for each hash function and independence between hashing functions. Furthermore, we generalize spherical hashing to support various similarity measures defined by kernel functions. Our extensive experiments show that our spherical hashing technique significantly outperforms state-of-the-art techniques based on hyperplanes across various benchmarks with sizes ranging from one to 75 million of GIST, BoW and VLAD descriptors. The performance gains are consistent and large, up to 100 percent improvements over the second best method among tested methods. These results confirm the unique merits of using hyperspheres to encode proximity regions in high-dimensional spaces. Finally, our method is intuitive and easy to implement.

  9. Collapsing spherical null shells in general relativity

    Directory of Open Access Journals (Sweden)

    S Khakshournia

    2011-03-01

    Full Text Available In this work, the gravitational collapse of a spherically symmetric null shell with the flat interior and a charged Vaidya exterior spacetimes is studied. There is no gravitational impulsive wave present on the null hypersurface which is shear-free and contracting. It follows that there is a critical radius at which the shell bounces and starts expanding.

  10. Modeling Ion-Exchange Processing With Spherical Resins For Cesium Removal

    Energy Technology Data Exchange (ETDEWEB)

    Hang, T.; Nash, C. A.; Aleman, S. E.

    2012-09-19

    The spherical Resorcinol-Formaldehyde and hypothetical spherical SuperLig(r) 644 ion-exchange resins are evaluated for cesium removal from radioactive waste solutions. Modeling results show that spherical SuperLig(r) 644 reduces column cycling by 50% for high-potassium solutions. Spherical Resorcinol Formaldehyde performs equally well for the lowest-potassium wastes. Less cycling reduces nitric acid usage during resin elution and sodium addition during resin regeneration, therefore, significantly decreasing life-cycle operational costs. A model assessment of the mechanism behind ''cesium bleed'' is also conducted. When a resin bed is eluted, a relatively small amount of cesium remains within resin particles. Cesium can bleed into otherwise decontaminated product in the next loading cycle. The bleed mechanism is shown to be fully isotherm-controlled vs. mass transfer controlled. Knowledge of residual post-elution cesium level and resin isotherm can be utilized to predict rate of cesium bleed in a mostly non-loaded column. Overall, this work demonstrates the versatility of the ion-exchange modeling to study the effects of resin characteristics on processing cycles, rates, and cold chemical consumption. This evaluation justifies further development of a spherical form of the SL644 resin.

  11. Surface functionalized hollow silica particles and composites

    KAUST Repository

    Rodionov, Valentin

    2017-05-26

    Composition comprising hollow spherical silica particles having outside particle walls and inside particle walls, wherein the particles have an average particle size of about 10 nm to about 500 nm and an average wall thickness of about 10 nm to about 50 nm; and wherein the particles are functionalized with at least one organic functional group on the outside particle wall, on the inside particle wall, or on both the outside and inside particle walls, wherein the organic functional group is in a reacted or unreacted form. The organic functional group can be epoxy. The particles can be mixed with polymer precursor or a polymer material such as epoxy to form a prepreg or a nanocomposite. Lightweight but strong materials can be formed. Low loadings of hollow particles can be used.

  12. Particle Pollution

    Science.gov (United States)

    ... Your Health Particle Pollution Public Health Issues Particle Pollution Recommend on Facebook Tweet Share Compartir Particle pollution — ... see them in the air. Where does particle pollution come from? Particle pollution can come from two ...

  13. Spherical crystallization: direct spherical agglomeration of salicylic Acid crystals during crystallization.

    Science.gov (United States)

    Kawashima, Y; Okumura, M; Takenaka, H

    1982-06-04

    Direct spherical agglomeration of salicylic acid crystals during crystallization is described. The needle-like salicylic acid crystals simultaneously form and agglomerate in a mixture of three partially miscible liquids, such as water, ethanol, and chloroform, with agitation. The agglomerates can be made directly into tablets because of their excellent flowability. Spherical crystallization could eliminate the usual separate agglomeration step after crystallization and may be adaptable to other pharmaceutical and chemical systems.

  14. An extension of spherical harmonics to region-based rotationally invariant descriptors for molecular shape description and comparison.

    Science.gov (United States)

    Mak, Lora; Grandison, Scott; Morris, Richard J

    2008-04-01

    The use of spherical harmonics in the molecular sciences is widespread. They have been employed with success in, for instance, the crystallographic fast rotation function, small-angle scattering particle reconstruction, molecular surface visualisation, protein-protein docking, active site analysis and protein function prediction. An extension of the spherical harmonic expansion method is presented here that enables regions (bodies) rather than contours (surfaces) to be described and which lends itself favourably to the construction of rotationally invariant shape descriptors. This method introduces a radial term that extends the spherical harmonics to 3D polynomials. These polynomials maintain the advantages of the spherical harmonics (orthonormality, completeness, uniqueness and fast computation) but correct the drawbacks (contour based shape description and star-shape objects) and give rise to powerful invariant descriptors. We provide proof-of-principle examples illustrating the potential of this method for accurate object representation, an analysis of the descriptor classification power, and comparisons to other methods.

  15. Halo formation and emittance growth in the transport of spherically symmetric mismatched bunched beams

    Energy Technology Data Exchange (ETDEWEB)

    Corrêa da Silva, Thales M., E-mail: thalestr@gmail.com; Pakter, Renato; Rizzato, Felipe B.; Levin, Yan [Instituto de Física, Universidade Federal do Rio Grande do Sul, Caixa Postal 15051, 91501-970 Porto Alegre, Rio Grande do Sul (Brazil)

    2015-02-15

    The effect of an initial envelope mismatch on the transport of bunched spherically symmetric beams is investigated. A particle-core model is used to estimate the maximum radius that halo particles can reach. The theory is used to obtain an empirical formula that provides the halo size as a function of system parameters. Taking into account, the incompressibility property of the Vlasov dynamics and the resulting Landau damping, an explicit form for the final stationary distribution attained by the beam is proposed. The distribution is fully self-consistent, presenting no free fitting parameters. The theory is used to predict the relevant beam transport properties, such as the final particle density distribution, the emittance growth, and the fraction of particles that will be expelled to form halo. The theoretical results are compared to the explicit N-particle dynamics simulations, showing a good agreement.

  16. MODEL FOR CALCULATING EFFECTIVE PARAMETERS OF MATRIX COMPOSITES FROM BI-ISOTROPIC PARTICLES WITH REGARD MULTIPLE REFLECTIONS OF ELECTROMAGNETIC FIELD

    National Research Council Canada - National Science Library

    V. T. Erofeenko

    2015-01-01

    .... Under the calculations of parameters, taking into account a multiple scattering of the field between particles, a new type of addition theorems, connecting basic spherical electromagnetic fields...

  17. Entropy-driven formation of large icosahedral colloidal clusters by spherical confinement

    Science.gov (United States)

    de Nijs, Bart; Dussi, Simone; Smallenburg, Frank; Meeldijk, Johannes D.; Groenendijk, Dirk J.; Filion, Laura; Imhof, Arnout; van Blaaderen, Alfons; Dijkstra, Marjolein

    2015-01-01

    Icosahedral symmetry, which is not compatible with truly long-range order, can be found in many systems, such as liquids, glasses, atomic clusters, quasicrystals and virus-capsids. To obtain arrangements with a high degree of icosahedral order from tens of particles or more, interparticle attractive interactions are considered to be essential. Here, we report that entropy and spherical confinement suffice for the formation of icosahedral clusters consisting of up to 100,000 particles. Specifically, by using real-space measurements on nanometre- and micrometre-sized colloids, as well as computer simulations, we show that tens of thousands of hard spheres compressed under spherical confinement spontaneously crystallize into icosahedral clusters that are entropically favoured over the bulk face-centred cubic crystal structure. Our findings provide insights into the interplay between confinement and crystallization and into how these are connected to the formation of icosahedral structures.

  18. Controlling particle properties in {{YBa}}_{2}{{Cu}}_{3}{{\\rm{O}}}_{7-\\delta } nanocomposites by combining PLD with an inert gas condensation system

    Science.gov (United States)

    Sparing, M.; Reich, E.; Hänisch, J.; Gottschall, T.; Hühne, R.; Fähler, S.; Rellinghaus, B.; Schultz, L.; Holzapfel, B.

    2017-10-01

    The critical current density {J}{{c}} in {{YBa}}2{{Cu}}3{{{O}}}7-δ thin films, which limits their application in external magnetic fields, can be enhanced by the introduction of artificial pinning centers such as non-superconducting nanoparticles inducing additional defects and local strain in the superconducting matrix. To understand the correlation between superconductivity, defect structures and particles, a controlled integration of particles with adjustable properties is essential. A powerful technique for the growth of isolated nanoparticles in the range of 10 nm is dc-magnetron sputtering in an inert gas flow. The inert gas condensation (IGC) of particles allows for an independent control of both the particle diameter distribution and the areal density. We report on the integration of such gas-phase-condensed {{HfO}}2 nanoparticles into pulsed laser deposited (PLD) {{YBa}}2{{Cu}}3{{{O}}}7-δ thin film multilayers with a combined PLD-IGC system. The particles and the structure of the multilayers are analyzed by transmission electron microscopy on cross-sectional FIB lamellae. As a result of the IGC particle implementation, randomly as well as biaxially oriented {{BaHfO}}3 precipitates are formed in the {{YBa}}2{{Cu}}3{{{O}}}7-δ thin films. With as few as three interlayers of nanoparticles, the pinning force density is enhanced in the low-field region.

  19. Sparse acoustic imaging with a spherical array

    DEFF Research Database (Denmark)

    Fernandez Grande, Efren; Xenaki, Angeliki

    2015-01-01

    In recent years, a number of methods for sound source localization and sound field reconstruction with spherical microphone arrays have been proposed. These arrays have properties that are potentially very useful, e.g. omni-directionality, robustness, compensable scattering, etc. This paper...... proposes a plane wave expansion method based on measurements with a spherical microphone array, and solved in the framework provided by Compressed Sensing. The proposed methodology results in a sparse solution, i.e. few non-zero coefficients, and it is suitable for both source localization and sound field...... reconstruction. In general it provides fine spatial resolution for localization (delta-like functions), and robust reconstruction (the noisy components are naturally suppressed). The validity and performance of the proposed method is examined, and its limitations as well as the underlying assumptions...

  20. Imaging with spherically bent crystals or reflectors

    Science.gov (United States)

    Bitter, M.; Delgado Aparicio, L. F.; Hill, K. W.; Scott, S.; Ince-Cushman, A.; Reinke, M.; Podpaly, Y.; Rice, J. E.; Beiersdorfer, P.; Wang, E.

    2010-07-01

    This paper consists of two parts: part I describes the working principle of a recently developed x-ray imaging crystal spectrometer, where the astigmatism of spherically bent crystals is being used with advantage to record spatially resolved spectra of highly charged ions for Doppler measurements of the ion-temperature and toroidal plasma-rotation-velocity profiles in tokamak plasmas. This type of spectrometer was thoroughly tested on NSTX and Alcator C-Mod, and its concept was recently adopted for the design of the ITER crystal spectrometers. Part II describes imaging schemes, where the astigmatism has been eliminated by the use of matched pairs of spherically bent crystals or reflectors. These imaging schemes are applicable over a wide range of the electromagnetic radiation, which includes microwaves, visible light, EUV radiation and x-rays. Potential applications with EUV radiation and x-rays are the diagnosis of laser-produced plasmas, imaging of biological samples with synchrotron radiation and lithography.

  1. Quality metric for spherical panoramic video

    Science.gov (United States)

    Zakharchenko, Vladyslav; Choi, Kwang Pyo; Park, Jeong Hoon

    2016-09-01

    Virtual reality (VR)/ augmented reality (AR) applications allow users to view artificial content of a surrounding space simulating presence effect with a help of special applications or devices. Synthetic contents production is well known process form computer graphics domain and pipeline has been already fixed in the industry. However emerging multimedia formats for immersive entertainment applications such as free-viewpoint television (FTV) or spherical panoramic video require different approaches in content management and quality assessment. The international standardization on FTV has been promoted by MPEG. This paper is dedicated to discussion of immersive media distribution format and quality estimation process. Accuracy and reliability of the proposed objective quality estimation method had been verified with spherical panoramic images demonstrating good correlation results with subjective quality estimation held by a group of experts.

  2. CONDENSATE DEFORMATION AT FORMATION AND ACTIVATED AGGLOMERATION OF SPHERICAL POWDERS AT PRODUCTION OF POROUS MATERIALS

    Directory of Open Access Journals (Sweden)

    P. A. Vityaz

    2012-01-01

    Full Text Available The variant of solution of the problem of porous powder materials production of spherical powders of corrosion-resistant steel with use of the complex technology combining development of nanotechnology, enabling to put on powder particles surfaces of condensate with thickness over 300 nanometers from layers of Si and mixture of elements (Si+C or (Mo+Si in the conditions of separate synthesis is offered.

  3. Phase behavior of charged hydrophobic colloids on flat and spherical surfaces

    Science.gov (United States)

    Kelleher, Colm P.

    For a broad class of two-dimensional (2D) materials, the transition from isotropic fluid to crystalline solid is described by the theory of melting due to Kosterlitz, Thouless, Halperin, Nelson and Young (KTHNY). According to this theory, long-range order is achieved via elimination of the topological defects which proliferate in the fluid phase. However, many natural and man-made 2D systems posses spatial curvature and/or non-trivial topology, which require the presence of topological defects, even at T=0. In principle, the presence of these defects could profoundly affect the phase behavior of such a system. In this thesis, we develop and characterize an experimental system of charged colloidal particles that bind electrostatically to the interface between an oil and an aqueous phase. Depending on how we prepare the sample, this fluid interface may be flat, spherical, or have a more complicated geometry. Focusing on the cases where the interface is flat or spherical, we measure the interactions between the particles, and probe various aspects of their phase behavior. On flat interfaces, this phase behavior is well-described by KTHNY theory. In spherical geometries, however, we observe spatial structures and inhomogeneous dynamics that cannot be captured by the measures traditionally used to describe flat-space phase behavior. We show that, in the spherical system, ordering is achieved by a novel mechanism: sequestration of topological defects into freely-terminating grain boundaries ("scars"), and simultaneous spatial organization of the scars themselves on the vertices of an icosahedron. The emergence of icosahedral order coincides with the localization of mobility into isolated "lakes" of fluid or glassy particles, situated at the icosahedron vertices. These lakes are embedded in a rigid, connected "continent" of locally crystalline particles.

  4. Investigation of spherical and cylindrical catural Iridium targets by photonuclear reaction

    Directory of Open Access Journals (Sweden)

    Korkmaz Mehmet Emin

    2017-01-01

    Full Text Available In this study, natural iridium consisting of Ir-191 and Ir-193 isotopes has been irradiated with 21 MeV photons. The distribution of photons, electrons and neutrons fluxes in the spherical and cylindrical natural iridium target have been calculated using MCNPX 2.7.0 Monte Carlo code. The intensity of the photon fluxes on both targets has been compared to the 106 particle story by showing them as mesh and optimizing the two targets.

  5. Effect of particle nonsphericity on bidirectional reflectance of cirrus clouds

    Energy Technology Data Exchange (ETDEWEB)

    Mishchenko, M.I.; Rossow, W.B.; Macke, A.; Lacis, A.A. [Goddard Institute for Space Studies, New York, NY (United States)

    1996-04-01

    This paper describes the use of the fractal ice particle method to study the differences in bidirectional reflectance caused by the differences in the single scattering phase functions of spherical water droplets and nonspherical ice crystals.

  6. The acceleration of solid particles subjected to cavitation nucleation

    DEFF Research Database (Denmark)

    Borkent, B.M.; Arora, M.; Ohl, C.-D.

    2008-01-01

    The cavity -particle dynamics at cavitation inception on the surface of spherical particles suspended in water and exposed to a strong tensile stress wave is experimentally studied with high-speed photography. Particles, which serve as nucleation sites for cavitation bubbles, are set into a fast...

  7. Technical notes. Spherical harmonics approximations of neutron transport

    Energy Technology Data Exchange (ETDEWEB)

    Demeny, A.; Dede, K.M.; Erdei, K.

    1976-12-01

    A double-range spherical harmonics approximation obtained by expanding the angular flux separately in the two regions combined with the conventional single-range spherical harmonics is found to give superior description of neutron transport.

  8. Dynamics and control of vibratory gyroscopes with special spherical symmetry

    CSIR Research Space (South Africa)

    Shatalov, M

    2006-01-01

    Full Text Available are obtained in the spherical Bessel and the associated Legendre functions, the effects of rotation are investigated and scales factors are determined for different vibrating modes of the spherical body, spheroidal and torsional. Corresponding scales factors...

  9. Spherical Cancer Models in Tumor Biology

    Directory of Open Access Journals (Sweden)

    Louis-Bastien Weiswald

    2015-01-01

    Full Text Available Three-dimensional (3D in vitro models have been used in cancer research as an intermediate model between in vitro cancer cell line cultures and in vivo tumor. Spherical cancer models represent major 3D in vitro models that have been described over the past 4 decades. These models have gained popularity in cancer stem cell research using tumorospheres. Thus, it is crucial to define and clarify the different spherical cancer models thus far described. Here, we focus on in vitro multicellular spheres used in cancer research. All these spherelike structures are characterized by their well-rounded shape, the presence of cancer cells, and their capacity to be maintained as free-floating cultures. We propose a rational classification of the four most commonly used spherical cancer models in cancer research based on culture methods for obtaining them and on subsequent differences in sphere biology: the multicellular tumor spheroid model, first described in the early 70s and obtained by culture of cancer cell lines under nonadherent conditions; tumorospheres, a model of cancer stem cell expansion established in a serum-free medium supplemented with growth factors; tissue-derived tumor spheres and organotypic multicellular spheroids, obtained by tumor tissue mechanical dissociation and cutting. In addition, we describe their applications to and interest in cancer research; in particular, we describe their contribution to chemoresistance, radioresistance, tumorigenicity, and invasion and migration studies. Although these models share a common 3D conformation, each displays its own intrinsic properties. Therefore, the most relevant spherical cancer model must be carefully selected, as a function of the study aim and cancer type.

  10. Marching Cubes in Cylindrical and Spherical Coordinates

    Science.gov (United States)

    Goldsmith, J.; Jacobson, A. S.

    1996-01-01

    Isosurface extraction is a common analysis and visualization technique for three-dimensional scalar data. Marching Cubes is the most commonly-used algorithm for finding polygonal representations of isosurfaces in such data. We extend Marching Cubes to produce geometry for data sets that lie in spherical and cylindrical coordinate systems as well as show the steps for derivation of transformations for other coordinate systems.

  11. Indentation of pressurized viscoplastic polymer spherical shells

    DEFF Research Database (Denmark)

    Tvergaard, Viggo; Needleman, A.

    2016-01-01

    The indentation response of polymer spherical shells is investigated. Finite deformation analyses are carried out with the polymer characterized as a viscoelastic/viscoplastic solid. Both pressurized and unpressurized shells are considered. Attention is restricted to axisymmetric deformations...... large strains are attained. The transition from an indentation type mode of deformation to a structural mode of deformation involving bending that occurs as the indentation depth increases is studied. The results show the effects of shell thickness, internal pressure and polymer constitutive...

  12. The Quest for the Most Spherical Bubble

    CERN Document Server

    Obreschkow, Danail; Dorsaz, Nicolas; Kobel, Philippe; de Bosset, Aurele; Farhat, Mohamed

    2013-01-01

    We describe a recently realized experiment producing the most spherical cavitation bubbles today. The bubbles grow inside a liquid from a point-plasma generated by a nanosecond laser pulse. Unlike in previous studies, the laser is focussed by a parabolic mirror, resulting in a plasma of unprecedented symmetry. The ensuing bubbles are sufficiently spherical that the hydrostatic pressure gradient caused by gravity becomes the dominant source of asymmetry in the collapse and rebound of the cavitation bubbles. To avoid this natural source of asymmetry, the whole experiment is therefore performed in microgravity conditions (ESA, 53rd and 56th parabolic flight campaign). Cavitation bubbles were observed in microgravity (~0g), where their collapse and rebound remain spherical, and in normal gravity (1g) to hyper-gravity (1.8g), where a gravity-driven jet appears. Here, we describe the experimental setup and technical results, and overview the science data. A selection of high-quality shadowgraphy movies and time-res...

  13. Fusion potential for spherical and compact tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Sandzelius, Mikael

    2003-02-01

    The tokamak is the most successful fusion experiment today. Despite this, the conventional tokamak has a long way to go before being realized into an economically viable power plant. In this master thesis work, two alternative tokamak configurations to the conventional tokamak has been studied, both of which could be realized to a lower cost. The fusion potential of the spherical and the compact tokamak have been examined with a comparison of the conventional tokamak in mind. The difficulties arising in the two configurations have been treated from a physical point of view concerning the fusion plasma and from a technological standpoint evolving around design, materials and engineering. Both advantages and drawbacks of either configuration have been treated relative to the conventional tokamak. The spherical tokamak shows promising plasma characteristics, notably a high {beta}-value but have troubles with high heat loads and marginal tritium breeding. The compact tokamak operates at a high plasma density and a high magnetic field enabling it to be built considerably smaller than any other tokamak. The most notable down-side being high heat loads and neutron transport problems. With the help of theoretical reactor studies, extrapolating from where we stand today, it is conceivable that the spherical tokamak is closer of being realized of the two. But, as this study shows, the compact tokamak power plant concept offers the most appealing prospect.

  14. Spherically symmetric thick branes cosmological evolution

    Science.gov (United States)

    Bernardini, A. E.; Cavalcanti, R. T.; da Rocha, Roldão

    2015-01-01

    Spherically symmetric time-dependent solutions for the 5D system of a scalar field canonically coupled to gravity are obtained and identified as an extension of recent results obtained by Ahmed et al. (JHEP 1404:061. arXiv:1312.3576 [hep-th], 2014). The corresponding cosmology of models with regularized branes generated by such a 5D scalar field scenario is also investigated. It has been shown that the anisotropic evolution of the warp factor and consequently the Hubble like parameter are both driven by the radial coordinate on the brane, which leads to an emergent thick brane-world scenario with spherically symmetric time dependent warp factor. Meanwhile, the separability of variables depending on fifth dimension, , which is exhibited by the equations of motion, allows one to recover the extra dimensional profiles obtained in Ahmed et al. (2014), namely the extra dimensional part of the scale (warp) factor and the scalar field dependence on . Therefore, our results are mainly concerned with the time dependence of a spherically symmetric warp factor. Besides evincing possibilities for obtaining asymmetric stable brane-world scenarios, the extra dimensional profiles here obtained can also be reduced to those ones investigated in Ahmed et al. (2014).

  15. Effect of particle shape on colloid retention and release in saturated porous media.

    Science.gov (United States)

    Liu, Qiang; Lazouskaya, Volha; He, Qingxiang; Jin, Yan

    2010-01-01

    Colloidal particles of environmental concern often have nonspherical shapes. However, theories and models such as the classical filtration theory have been developed based on the behavior of spherical particles. This study examined the effect of particle shape on colloid retention (e.g., attachment and straining) and release in saturated porous media. Two- and three-step transport experiments were conducted in water-saturated glass bead columns using colloids dispersed in deionized water and an electrolyte solution. The particles used in the experiments were carboxylate-modified latex colloids of spherical (500 nm diam.) and rod (aspect ratio, 7.0) shapes. The rod-like particles were prepared by stretching the spherical particles. Analysis of the colloid breakthrough curves indicates that particle shape affected transport behavior, but retention did not increase with increasing aspect ratio. Retention of the spherical particles occurred mainly in the secondary energy minimum, whereas retention of rod-like particles occurred in primary and secondary energy minima. There was less straining of rod-like particles compared with spherical ones, indicating that the minor axis was the critical dimension controlling the process. Release of spherical particles on elution was instantaneous, whereas release of rod-like particles was rate limited, giving rise to long tails, implying an orientation effect for rod-like colloids. The results suggest that the differences in electrostatic properties and shape contributed to the observed different retention and release behaviors of the two colloids.

  16. Time-dependent correlation buildup in spherical Yukawa balls

    Science.gov (United States)

    Kaehlert, Hanno; Bonitz, Michael

    2009-11-01

    In recent years it has become possible to create 3D dust crystals in experiments [1], where the particles arrange on concentric spherical shells. Compared to confined ions the interaction between the dust particles is screened, which has been shown to affect the shell occupation of the ground state [2], and the probability of metastable states [3,4]. Here we study dynamical processes in a trapped Yukawa plasma by means of Langevin dynamics simulations, which fully include the Coulomb correlations, the confinement and friction with the neutral gas. By cooling a weakly correlated initial state towards the strong coupling regime, the formation of concentric shells is observed. While in systems with Coulomb interaction the shells clearly emerge at the cluster boundary, they appear almost simultaneously for sufficiently large screening. Monte Carlo simulations are used to show that the sequence, in which radial order is established, is determined by the confinement potential.[4pt] [1] O. Arp, D. Block, A. Piel, and A. Melzer, PRL 93, 165004 (2004)[0pt] [2] H. Baumgartner et al., New J. Phys. 10, 093019 (2008)[0pt] [3] D. Block et al., Phys. Plasmas 15, 040701 (2008)[0pt] [4] H. K"ahlert et al., Phys. Rev. E 78, 036408 (2008)

  17. Physics objectives of PI3 spherical tokamak program

    Science.gov (United States)

    Howard, Stephen; Laberge, Michel; Reynolds, Meritt; O'Shea, Peter; Ivanov, Russ; Young, William; Carle, Patrick; Froese, Aaron; Epp, Kelly

    2017-10-01

    Achieving net energy gain with a Magnetized Target Fusion (MTF) system requires the initial plasma state to satisfy a set of performance goals, such as particle inventory (1021 ions), sufficient magnetic flux (0.3 Wb) to confine the plasma without MHD instability, and initial energy confinement time several times longer than the compression time. General Fusion (GF) is now constructing Plasma Injector 3 (PI3) to explore the physics of reactor-scale plasmas. Energy considerations lead us to design around an initial state of Rvessel = 1 m. PI3 will use fast coaxial helicity injection via a Marshall gun to create a spherical tokamak plasma, with no additional heating. MTF requires solenoid-free startup with no vertical field coils, and will rely on flux conservation by a metal wall. PI3 is 5x larger than SPECTOR so is expected to yield magnetic lifetime increase of 25x, while peak temperature of PI3 is expected to be similar (400-500 eV) Physics investigations will study MHD activity and the resistive and convective evolution of current, temperature and density profiles. We seek to understand the confinement physics, radiative loss, thermal and particle transport, recycling and edge physics of PI3.

  18. Analysis of dark matter axion clumps with spherical symmetry

    Science.gov (United States)

    Schiappacasse, Enrico D.; Hertzberg, Mark P.

    2018-01-01

    Recently there has been much interest in the spatial distribution of light scalar dark matter, especially axions, throughout the universe. When the local gravitational interactions between the scalar modes are sufficiently rapid, it can cause the field to re-organize into a BEC of gravitationally bound clumps. While these clumps are stable when only gravitation is included, the picture is complicated by the presence of the axion's attractive self-interactions, which can potentially cause the clumps to collapse. Here we perform a detailed stability analysis to determine under what conditions the clumps are stable. In this paper we focus on spherical configurations, leaving aspherical configurations for future work. We identify branches of clump solutions of the axion-gravity-self-interacting system and study their stability properties. We find that clumps that are (spatially) large are stable, while clumps that are (spatially) small are unstable and may collapse. Furthermore, there is a maximum number of particles that can be in a clump. We map out the full space of solutions, which includes quasi-stable axitons, and clarify how a recent claim in the literature of a new ultra-dense branch of stable solutions rests on an invalid use of the non-relativistic approximation. We also consider repulsive self-interactions that may arise from a generic scalar dark matter candidate, finding a single stable branch that extends to arbitrary particle number.

  19. Ion beam-induced shaping of Ni nanoparticles embedded in a silica matrix: from spherical to prolate shape

    Directory of Open Access Journals (Sweden)

    Avasthi Devesh

    2011-01-01

    Full Text Available Abstract Present work reports the elongation of spherical Ni nanoparticles (NPs parallel to each other, due to bombardment with 120 MeV Au+9 ions at a fluence of 5 × 1013 ions/cm2. The Ni NPs embedded in silica matrix have been prepared by atom beam sputtering technique and subsequent annealing. The elongation of Ni NPs due to interaction with Au+9 ions as investigated by cross-sectional transmission electron microscopy (TEM shows a strong dependence on initial Ni particle size and is explained on the basis of thermal spike model. Irradiation induces a change from single crystalline nature of spherical particles to polycrystalline nature of elongated particles. Magnetization measurements indicate that changes in coercivity (Hc and remanence ratio (Mr/Ms are stronger in the ion beam direction due to the preferential easy axis of elongated particles in the beam direction.

  20. Spherical Arrays for Wireless Channel Characterization and Emulation

    DEFF Research Database (Denmark)

    Franek, Ondrej; Pedersen, Gert Frølund

    2014-01-01

    Three types of spherical arrays for use in wireless communication research are presented. First, a spherical array of 32 monopoles with beam steering in arbitrary direction and with arbitrary polarization is described. Next, a spherical array with 16 quad-ridged open-flared horns is introduced...

  1. PENETRATION OF A SOUND FIELD THROUGH A MULTILAYERED SPHERICAL SHELL

    Directory of Open Access Journals (Sweden)

    G. Ch. Shushkevich

    2013-01-01

    Full Text Available An analytical solution of the boundary problem describing the process of penetration of thesound field of a spherical emitter located inside a thin unclosed spherical shell through a permeable multilayered spherical shell is considered. The influence of some parameters of the problem on the value of the sound field weakening (screening coefficient is studied via a numerical simulation.

  2. Addition theorems for spin spherical harmonics: II. Results

    Energy Technology Data Exchange (ETDEWEB)

    Bouzas, Antonio O, E-mail: abouzas@mda.cinvestav.mx [Departamento de Fisica Aplicada, CINVESTAV-IPN, Carretera Antigua a Progreso Km. 6, Apdo. Postal 73 ' Cordemex' , Merida 97310, Yucatan (Mexico)

    2011-04-22

    Based on the results of part I (2011 J. Phys. A: Math. Theor. 44 165301), we obtain the general form of the addition theorem for spin spherical harmonics and give explicit results in the cases involving one spin-s' and one spin-s spherical harmonics with s', s = 1/2, 1, 3/2, and |s' - s| = 0, 1. We also obtain a fully general addition theorem for one scalar and one tensor spherical harmonic of arbitrary rank. A variety of bilocal sums of ordinary and spin spherical harmonics are given in explicit form, including a general explicit expression for bilocal spherical harmonics.

  3. Point massive particle in General Relativity

    Science.gov (United States)

    Katanaev, M. O.

    2013-10-01

    It is well known that the Schwarzschild solution describes the gravitational field outside compact spherically symmetric mass distribution in General Relativity. In particular, it describes the gravitational field outside a point particle. Nevertheless, what is the exact solution of Einstein's equations with -type source corresponding to a point particle is not known. In the present paper, we prove that the Schwarzschild solution in isotropic coordinates is the asymptotically flat static spherically symmetric solution of Einstein's equations with -type energy-momentum tensor corresponding to a point particle. Solution of Einstein's equations is understood in the generalized sense after integration with a test function. Metric components are locally integrable functions for which nonlinear Einstein's equations are mathematically defined. The Schwarzschild solution in isotropic coordinates is locally isometric to the Schwarzschild solution in Schwarzschild coordinates but differs essentially globally. It is topologically trivial neglecting the world line of a point particle. Gravity attraction at large distances is replaced by repulsion at the particle neighborhood.

  4. Preparation of functional spherical polysilsesquioxane/gold nanoparticle composites and their applications in DNA assay

    Science.gov (United States)

    Jung, Jung A.; Kim, Young Baek; Kim, Young A.; Ryu, Seung Bum; Kim, Veronica

    2011-06-01

    Functional spherical solid and hollow particles of polysilsesquioxanes (PSQs) containing amine, thiol, and vinyl groups were prepared by polymerizing organotrialkoxysilanes (OTASs) containing corresponding chemical groups. Fluorescent PSQ particles were prepared by physically entrapping Rhodamine 6G, Coumarin 7, and Fluoresceine sodium salts. The intensity of fluorescent light increased initially with increasing amount of entrapped fluorophores and then leveled off or decreased slightly after reaching a maximum value. PSQ particles containing gold nanoparticles (GNPs), both inside and on the surface, were prepared by the in situ reduction of gold ions by the PSQ particles. When the reduction reaction was carried out for extended periods of time, the GNP that had formed inside the poly(3-mercaptopropyl)silsesquioxane (PMPSQ) and polyvinylsilsesequioxane (PVSQ) particles underwent interesting morphological changes. PSQ particles containing amine and thiol groups fixed the GNPs on the surface, which could be utilized further in binding amine-modified oligo-DNA strands. The aggregation of PSQ/GNP particles combined with complementary oligo-DNA strands was examined to demonstrate that these particles could be applied to DNA assays and isolation. The particles were characterized by scanning electron microscopy, transmission electron microscopy, solid state nuclear magnetic resonance spectroscopy, ultraviolet/visible spectroscopy, and fluorescence microscopy.

  5. Size-Tunable Fe3O4 Spherical Nanoclusters Through a One-Pot Hydrothermal Synthesis.

    Science.gov (United States)

    Leshuk, Timothy; Krishnakumar, Harish; Gu, Frank

    2015-07-01

    A new method is presented for the synthesis of monodisperse, size-tunable Fe3O4 spherical nanocluster particles through a simple, one-step hydrothermal reaction, according to a kinetics-controlled self-assembly process of smaller nanocrystals into hierarchical mesoporous aggregates. The mean diameter of the particles can be controlled over a broad range up to ~230 nm by simply varying the concentration of the precipitating reagent (urea or ammonia). The particles can be easily dispersed in water with excellent colloidal stability, exhibit a high surface area of ~ 60 m2 g(-1), and demonstrate size-dependent magnetic separation kinetics, where the larger nanoclusters exhibit rapid magnetophoresis, and the smaller nanoclusters remain inseparable. Thus particle size control is essential for improving magnetic separation processes.

  6. Boron Neutron Capture Therapy (BNCT) Dose Calculation using Geometrical Factors Spherical Interface for Glioblastoma Multiforme

    Science.gov (United States)

    Zasneda, Sabriani; Widita, Rena

    2010-06-01

    Boron Neutron Capture Therapy (BNCT) is a cancer therapy by utilizing thermal neutron to produce alpha particles and lithium nuclei. The superiority of BNCT is that the radiation effects could be limited only for the tumor cells. BNCT radiation dose depends on the distribution of boron in the tumor. Absorbed dose to the cells from the reaction 10B (n, α) 7Li was calculated near interface medium containing boron and boron-free region. The method considers the contribution of the alpha particle and recoiled lithium particle to the absorbed dose and the variation of Linear Energy Transfer (LET) charged particles energy. Geometrical factor data of boron distribution for the spherical surface is used to calculate the energy absorbed in the tumor cells, brain and scalp for case Glioblastoma Multiforme. The result shows that the optimal dose in tumor is obtained for boron concentrations of 22.1 mg 10B/g blood.

  7. Compressive sensing with a spherical microphone array

    DEFF Research Database (Denmark)

    Fernandez Grande, Efren; Xenaki, Angeliki

    2016-01-01

    A wave expansion method is proposed in this work, based on measurements with a spherical microphone array, and formulated in the framework provided by Compressive Sensing. The method promotes sparse solutions via ‘1-norm minimization, so that the measured data are represented by few basis functions....... This results in fine spatial resolution and accuracy. This publication covers the theoretical background of the method, including experimental results that illustrate some of the fundamental differences with the “conventional” leastsquares approach. The proposed methodology is relevant for source localization...

  8. Static spherical metrics: a geometrical approach

    Science.gov (United States)

    Tiwari, A. K.; Maharaj, S. D.; Narain, R.

    2017-08-01

    There exist several solution generating algorithms for static spherically symmetric metrics. Here we use the geometrical approach of Lie point symmetries to solve the condition of pressure isotropy by finding the associated five-dimensional Lie algebra of symmetry generators. For the non-Abelian subalgebras the underlying equation is solved to obtain a general solution. Contained within this class are vacuum models, constant density models, metrics with linear equations of state and the Buchdahl representation of the polytrope with index five. For a different particular symmetry generator the condition of pressure isotropy is transformed to a Riccati equation which admits particular solutions.

  9. Spherical conformal models for compact stars

    Energy Technology Data Exchange (ETDEWEB)

    Takisa, P.M.; Maharaj, S.D.; Manjonjo, A.M.; Moopanar, S. [University of KwaZulu-Natal, Astrophysics and Cosmology Research Unit, School of Mathematics, Statistics and Computer Science, Durban (South Africa)

    2017-10-15

    We consider spherical exact models for compact stars with anisotropic pressures and a conformal symmetry. The conformal symmetry condition generates an integral relationship between the gravitational potentials. We solve this condition to find a new anisotropic solution to the Einstein field equations. We demonstrate that the exact solution produces a relativistic model of a compact star. The model generates stellar radii and masses consistent with PSR J1614-2230, Vela X1, PSR J1903+327 and Cen X-3. A detailed physical examination shows that the model is regular, well behaved and stable. The mass-radius limit and the surface red shift are consistent with observational constraints. (orig.)

  10. The Spherical Bolometric Albedo of Planet Mercury

    OpenAIRE

    Mallama, Anthony

    2017-01-01

    Published reflectance data covering several different wavelength intervals has been combined and analyzed in order to determine the spherical bolometric albedo of Mercury. The resulting value of 0.088 +/- 0.003 spans wavelengths from 0 to 4 {\\mu}m which includes over 99% of the solar flux. This bolometric result is greater than the value determined between 0.43 and 1.01 {\\mu}m by Domingue et al. (2011, Planet. Space Sci., 59, 1853-1872). The difference is due to higher reflectivity at wavelen...

  11. VORTEX FLOW INSIDE THE DEEP SPHERICAL DIMPLE

    Directory of Open Access Journals (Sweden)

    В. Воскобійник

    2012-04-01

    Full Text Available The results of experimental researches of the forming features of the vortex flow which is formed at the turbulentflow above of the deep spherical dimple are presented. Visualization shows that inclined asymmetric large-scale vortices are generated inside the dimple. These vortex structures are switched from one tilt in other, exciting lowfrequencyoscillations. During an evolution the asymmetric vortices are broken up above an aft wall of the dimple andthe angle of their incline and break up is increased with the growth of Reynolds number.

  12. Discrete analogues in harmonic analysis: Spherical averages

    OpenAIRE

    Magyar, A; Stein, E. M.; Wainger, S.

    2004-01-01

    In this paper we prove an analogue in the discrete setting of \\Bbb Z^d, of the spherical maximal theorem for \\Bbb R^d. The methods used are two-fold: the application of certain "sampling" techniques, and ideas arising in the study of the number of representations of an integer as a sum of d squares in particular, the "circle method". The results we obtained are by necessity limited to d \\ge 5, and moreover the range of p for the L^p estimates differs from its analogue in \\Bbb R^d.

  13. The dynamo bifurcation in rotating spherical shells

    CERN Document Server

    Morin, Vincent; 10.1142/S021797920906378X

    2010-01-01

    We investigate the nature of the dynamo bifurcation in a configuration applicable to the Earth's liquid outer core, i.e. in a rotating spherical shell with thermally driven motions. We show that the nature of the bifurcation, which can be either supercritical or subcritical or even take the form of isola (or detached lobes) strongly depends on the parameters. This dependence is described in a range of parameters numerically accessible (which unfortunately remains remote from geophysical application), and we show how the magnetic Prandtl number and the Ekman number control these transitions.

  14. Formability of spherical and large aluminum sheets

    Science.gov (United States)

    Zimmermann, F.; Brosius, A.; Beyer, E.; Standfuß, J.; Jahn, A.

    2017-10-01

    The novel aluminum alloy AlMgSc (AA5028) shows a high potential for aeronautical applications, especially to replace the currently used material for structural components within metallic aircraft fuselages [1]. As AlMgSc sheets cannot be stretch formed at room temperature due to cracking in the clamping zones, an alternative technology called "creep-forming" was investigated by Jambu [2]. Nevertheless, creep-forming is only applicable for panels to be formed in moulds with small curvatures, because shaping double-curved geometries with small radii of curvature tends to buckling [3]. Hence, the formability of large spherical aluminum sheets as double-curved geometries is investigated.

  15. Analysis of particle kinematics in spheronization via particle image velocimetry.

    Science.gov (United States)

    Koester, Martin; Thommes, Markus

    2013-02-01

    Spheronization is a wide spread technique in pellet production for many pharmaceutical applications. Pellets produced by spheronization are characterized by a particularly spherical shape and narrow size distribution. The particle kinematic during spheronization is currently not well-understood. Therefore, particle image velocimetry (PIV) was implemented in the spheronization process to visualize the particle movement and to identify flow patterns, in order to explain the influence of various process parameters. The spheronization process of a common formulation was recorded with a high-speed camera, and the images were processed using particle image velocimetry software. A crosscorrelation approach was chosen to determine the particle velocity at the surface of the pellet bulk. Formulation and process parameters were varied systematically, and their influence on the particle velocity was investigated. The particle stream shows a torus-like shape with a twisted rope-like motion. It is remarkable that the overall particle velocity is approximately 10-fold lower than the tip speed of the friction plate. The velocity of the particle stream can be correlated to the water content of the pellets and the load of the spheronizer, while the rotation speed was not relevant. In conclusion, PIV was successfully applied to the spheronization process, and new insights into the particle velocity were obtained. Copyright © 2012 Elsevier B.V. All rights reserved.

  16. Spherically symmetric conformal gravity and "gravitational bubbles"

    CERN Document Server

    Berezin, V A; Eroshenko, Yu N

    2016-01-01

    The general structure of the spherically symmetric solutions in the Weyl conformal gravity is described. The corresponding Bach equation are derived for the special type of metrics, which can be considered as the representative of the general class. The complete set of the pure vacuum solutions is found. It consists of two classes. The first one contains the solutions with constant two-dimensional curvature scalar of our specific metrics, and the representatives are the famous Robertson-Walker metrics. One of them we called the "gravitational bubbles", which is compact and with zero Weyl tensor. The second class is more general, with varying curvature scalar. We found its representative as the one-parameter family. It appears that it can be conformally covered by the thee-parameter Mannheim-Kazanas solution. We also investigated the general structure of the energy-momentum tensor in the spherical conformal gravity and constructed the vectorial equation that reveals clearly the same features of non-vacuum solu...

  17. Initial assessments of ignition spherical torus

    Energy Technology Data Exchange (ETDEWEB)

    Peng, Y.K.M.; Borowski, S.K.; Bussell, G.T.; Dalton, G.R.; Gorker, G.E.; Haines, J.R.; Hamilton, W.R.; Kalsi, S.S.; Lee, V.D.; Miller, J.B.

    1985-12-01

    Initial assessments of ignition spherical tori suggest that they can be highly cost effective and exceptionally small in unit size. Assuming advanced methods of current drive to ramp up the plasma current (e.g., via lower hybrid wave at modest plasma densities and temperatures), the inductive solenoid can largely be eliminated. Given the uncertainties in plasma energy confinement times and the effects of strong paramagnetism on plasma pressure, and allowing for the possible use of high-strength copper alloys (e.g., C-17510, Cu-Ni-Be alloy), ignition spherical tori with a 50-s burn are estimated to have major radii ranging from 1.0 to 1.6 m, aspect ratios from 1.4 to 1.7, vacuum toroidal fields from 2 to 3 T, plasma currents from 10 to 19 MA, and fusion power from 50 to 300 MW. Because of its modest field strength and simple poloidal field coil configuration, only conventional engineering approaches are needed in the design. A free-standing toroidal field coil/vacuum vessel structure is assessed to be feasible and relatively independent of the shield structure and the poloidal field coils. This exceptionally simple configuration depends significantly, however, on practical fabrication approaches of the center conductor post, about which there is presently little experience. 19 refs.

  18. Flow and scour around spherical bodies

    DEFF Research Database (Denmark)

    Truelsen, Christoffer

    2003-01-01

    near an erodible bed. In Chapter 2, a 3-D Reynolds-Average Navier-Stokes (RANS) flow solver has been used to simulate flow around and forces on a free and a near-wall sphere. Fluid forces are computed and validated against experimental data. A good agreement is found between the model and experimental...... results except in the critical flow regime. For flow around a near-wall sphere, a weak horseshoe vortex emerges as the gap ratio becomes less than or equal to 0.3. In Chapter 3, a RANS flow solver has been used to compute the bed shear stress for a near-wall sphere. The model results compare well......Spherical bodies placed in the marine environment may bury themselves due to the action of the waves and the current on the sediment in their immediate neighborhood. The present study addresses this topic by a numerical and an experimental investigation of the flow and scour around a spherical body...

  19. SPHERICAL INDENTATION OF SiC

    Energy Technology Data Exchange (ETDEWEB)

    Wereszczak, Andrew A [ORNL; Johanns, Kurt E [ORNL

    2007-01-01

    Instrumented Hertzian indentation testing was performed on several grades of SiCs and the results and preliminary interpretations are presented. The grades included hot-pressed and sintered compositions. One of the hot-pressed grades was additionally subjected to high temperature heat treatment to produce a coarsened grain microstructure to enable the examination of exaggerated grain size on indentation response. Diamond spherical indenters were used in the testing. Indentation load, indentation depth of penetration, and acoustic activity were continually measured during each indentation test. Indentation response and postmortem analysis of induced damage (e.g., ring/cone, radial and median cracking, quasi-plasticity) are compared and qualitatively as a function of grain size. For the case of SiC-N, the instrumented spherical indentation showed that yielding initiated at an average contact stress 12-13 GPa and that there was another event (i.e., a noticeable rate increase in compliance probably associated with extensive ring and radial crack formations) occurring around an estimated average contact stress of 19 GPa.

  20. Pairwise Interaction Extended Point-Particle (PIEP) model for multiphase jets and sedimenting particles

    Science.gov (United States)

    Liu, Kai; Balachandar, S.

    2017-11-01

    We perform a series of Euler-Lagrange direct numerical simulations (DNS) for multiphase jets and sedimenting particles. The forces the flow exerts on the particles in these two-way coupled simulations are computed using the Basset-Bousinesq-Oseen (BBO) equations. These forces do not explicitly account for particle-particle interactions, even though such pairwise interactions induced by the perturbations from neighboring particles may be important especially when the particle volume fraction is high. Such effects have been largely unaddressed in the literature. Here, we implement the Pairwise Interaction Extended Point-Particle (PIEP) model to simulate the effect of neighboring particle pairs. A simple collision model is also applied to avoid unphysical overlapping of solid spherical particles. The simulation results indicate that the PIEP model provides a more elaborative and complicated movement of the dispersed phase (droplets and particles). Office of Naval Research (ONR) Multidisciplinary University Research Initiative (MURI) project N00014-16-1-2617.

  1. Finite element analysis of multi-particle impact on erosion in abrasive water jet machining of titanium alloy

    National Research Council Canada - National Science Library

    Kumar, Naresh; Shukla, Mukul

    2012-01-01

    ...) particle impact on erosion of Grade 5 Titanium alloy (Ti-6Al-4V). The influence of abrasive particle impact angle and velocity on the crater sphericity and depth, and erosion rate has been investigated...

  2. Expansion of arbitrary electromagnetic fields in terms of vector spherical wave functions.

    Science.gov (United States)

    Moreira, Wendel Lopes; Neves, Antonio Alvaro Ranha; Garbos, Martin K; Euser, Tijmen G; Cesar, Carlos Lenz

    2016-02-08

    Since 1908, when Mie reported analytical expressions for the fields scattered by a spherical particle upon incidence of plane-waves, generalizing his analysis for the case of an arbitrary incident wave has been an open question because of the cancellation of the prefactor radial spherical Bessel function. This cancellation was obtained before by our own group for a highly focused beam centered in the objective. In this work, however, we show for the first time how these terms can be canceled out for any arbitrary incident field that satisfies Maxwells equations, and obtain analytical expressions for the beam shape coefficients. We show several examples on how to use our method to obtain analytical beam shape coefficients for: Bessel beams, general hollow waveguide modes and specific geometries such as cylindrical and rectangular. Our method uses the vector potential, which shows the interesting characteristic of being gauge invariant. These results are highly relevant for speeding up numerical calculation of light scattering applications such as the radiation forces acting on spherical particles placed in an arbitrary electromagnetic field, as in an optical tweezers system.

  3. Simulation of light scattering from surfaces containing spherical and elliptical nanoparticles

    Science.gov (United States)

    Tausendfreund, A.; Mader, D.; Simon, S.; Patzelt, S.; Goch, G.

    2006-04-01

    This paper presents a simulation approach for light scattering from surfaces containing spherical and elliptical nanoparticles. For this approach an electrically equivalent macro model is derived based on the analytical solutions of Maxwell's equations (e.g. Mie's solution of a sphere). These macro models do not necessarily fulfill the boundary conditions or give the correct near-field but they provide a suitable far-field solution. The benefit of this approach is an abstract model for the far-field computation that is much more efficient than known solutions like FEM. The radiation sources at the surface are reduced to a maximum like a single source for a whole particle, which gives the correct far-field but does not fulfill the boundary conditions. For the set of radiation sources used for the macro models the approach presented here reverts to the accurate computation of simple geometries. In this special case of spherical and elliptical particles the solution of the Mie theory can be used. In this paper it is shown that in the case of nanostructures the far-field of a sphere and an ellipse can be replaced by the radiation field from a set of dipoles. Based on these results it is possible to approximate an equivalent macro model of the surface containing spherical and elliptical elements. The presented macro model provides a very reasonable simulation approach with acceptable simulation times for large surface areas of several square millimeters.

  4. Preparation of spherical ceria coated silica nanoparticle abrasives for CMP application

    Energy Technology Data Exchange (ETDEWEB)

    Peedikakkandy, Lekha [Department of Metallurgical Engineering and Materials Science, IIT Bombay, Powai, Mumbai 400076 (India); Kalita, Laksheswar [Advanced Technology Group, Applied Materials India Pvt. Ltd., Department of Electrical Engineering, IIT Bombay, Powai, Mumbai 400076 (India); Kavle, Pravin [Department of Metallurgical Engineering and Materials Science, IIT Bombay, Powai, Mumbai 400076 (India); Kadam, Ankur; Gujar, Vikas; Arcot, Mahesh [Advanced Technology Group, Applied Materials India Pvt. Ltd., Department of Electrical Engineering, IIT Bombay, Powai, Mumbai 400076 (India); Bhargava, Parag, E-mail: pbhargava@iitb.ac.in [Department of Metallurgical Engineering and Materials Science, IIT Bombay, Powai, Mumbai 400076 (India)

    2015-12-01

    Highlights: • Nano-layer coating of ceria over silica nanoparticles. • Study effect of reaction pH and temperature on ceria coating over silica nanoparticles. • CMP application of ceria coated silica nanoparticles over SiO{sub 2} and SiN films. - Abstract: This paper describes synthesis of spherical and highly mono-dispersed ceria coated silica nanoparticles of size ∼70–80 nm for application as abrasive particles in Chemical Mechanical Planarization (CMP) process. Core silica nanoparticles were initially synthesized using micro-emulsion method. Ceria coating on these ultrafine and spherical silica nanoparticles was achieved using controlled chemical precipitation method. Study of various parameters influencing the formation of ceria coated silica nanoparticles of size less than 100 nm has been undertaken and reported. Ceria coating over silica nanoparticles was varied by controlling the reaction temperature, pH and precursor concentrations. Characterization studies using X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Energy Dispersive X-ray analysis show formation of crystalline CeO{sub 2} coating of ∼10 nm thickness over silica with spherical morphology and particle size <100 nm. Aqueous slurry of ceria coated silica abrasive was prepared and employed for polishing of oxide and nitride films on silicon substrates. Polished films were studied using ellipsometry and an improvement in SiO{sub 2}:SiN selective removal rates up to 12 was observed using 1 wt% ceria coated silica nanoparticles slurry.

  5. Dynamics and interactions of particles in a thermophoretic trap

    Science.gov (United States)

    Foster, Benjamin; Fung, Frankie; Fieweger, Connor; Usatyuk, Mykhaylo; Gaj, Anita; DeSalvo, B. J.; Chin, Cheng

    2017-08-01

    We investigate dynamics and interactions of particles levitated and trapped by the thermophoretic force in a vacuum cell. Our analysis is based on footage taken by orthogonal cameras that are able to capture the three dimensional trajectories of the particles. In contrast to spherical particles, which remain stationary at the center of the cell, here we report new qualitative features of the motion of particles with non-spherical geometry. Singly levitated particles exhibit steady spinning around their body axis and rotation around the symmetry axis of the cell. When two levitated particles approach each other, repulsive or attractive interactions between the particles are observed. Our levitation system offers a wonderful platform to study interaction between particles in a microgravity environment.

  6. Effect of Mg-Zn-Nd spherical quasi-crystals on microstructure and mechanical properties of ZK60 alloy

    Directory of Open Access Journals (Sweden)

    Zhang Jinshan

    2011-08-01

    Full Text Available To improve the strength, toughness, heat-resistance and deformability of magnesium alloy, the microstructure and mechanical properties of ZK60 alloy strengthened by Mg-Zn-Nd spherical quasi-crystal phase (I-phase particles were investigated. Mg40Zn55Nd5 (I-phase particles in addition to α-Mg, MgZn phase and MgZn2 phases can be obtained in ZK60-based composites under normal casting condition by the addition of quasi-crystal containing Mg-Zn-Nd master alloy. The experimental results show that the introduction of Mg-Zn-Nd spherical quasi-crystal phase into ZK60 alloy makes a great contribution to the refinement of the matrix microstructures and the improvement of mechanical properties. While adding Mg-Zn-Nd spherical quasi-crystal master alloy of 4.0wt.%, the ultimate tensile strength and yield strength of ZK60-based composite at ambient temperature reach their peak values of 256.7 MPa and 150.4 MPa, which were about 17.8% and 24.1% higher respectively than those of the ZK60 alloy. The improved mechanical properties are mainly attributed to the pinning effect of the quasi-crystal particles (I-phase at the grain boundaries. This research results provide a new way for strengthening and toughening of magnesium alloys as well as a new application of Mg-based spherical quasi-crystals.

  7. Diffusion with moving boundary on spherical surfaces.

    Science.gov (United States)

    Amatore, Christian; Klymenko, Oleksiy V; Oleinick, Alexander I; Svir, Irina

    2009-07-13

    In this work, we illustrate two approaches to the simulation of surface diffusion over a sphere coupled with the formation of a cluster by reactive particles as a paradigm of a wide variety of problems occurring in many areas of nanosciences and biology. The problem is treated using a Brownian motion approach and a numerical solution of the corresponding continuous Fick's laws of diffusion. While being computationally more expensive, the Brownian motion approach allows one to consider a wider range of situations, particularly those corresponding to relatively high concentrations of diffusing particles and the ensuing problem of particle overlap when they are ascribed finite sizes.

  8. Spheronization process particle kinematics determined by discrete element simulations and particle image velocimentry measurements.

    Science.gov (United States)

    Koester, Martin; García, R Edwin; Thommes, Markus

    2014-12-30

    Spheronization is an important pharmaceutical manufacturing technique to produce spherical agglomerates of 0.5-2mm diameter. These pellets have a narrow size distribution and a spherical shape. During the spheronization process, the extruded cylindrical strands break in short cylinders and evolve from a cylindrical to a spherical state by deformation and attrition/agglomeration mechanisms. Using the discrete element method, an integrated modeling-experimental framework is presented, that captures the particle motion during the spheronization process. Simulations were directly compared and validated against particle image velocimetry (PIV) experiments with monodisperse spherical and dry γ-Al2O3 particles. demonstrate a characteristic torus like flow pattern, with particle velocities about three times slower than the rotation speed of the friction plate. Five characteristic zones controlling the spheronization process are identified: Zone I, where particles undergo shear forces that favors attrition and contributes material to the agglomeration process; Zone II, where the static wall contributes to the mass exchange between particles; Zone III, where gravitational forces combined with particle motion induce particles to collide with the moving plate and re-enter Zone I; Zone IV, where a subpopulation of particles are ejected into the air when in contact with the friction plate structure; and Zone V where the low poloidal velocity favors a stagnant particle population and is entirely controlled by the batch size. These new insights in to the particle motion are leading to deeper process understanding, e.g., the effect of load and rotation speed to the pellet formation kinetics. This could be beneficial for the optimization of a manufacturing process as well as for the development of new formulations. Copyright © 2014 Elsevier B.V. All rights reserved.

  9. Shape evolution of a melting nonspherical particle.

    Science.gov (United States)

    Kintea, Daniel M; Hauk, Tobias; Roisman, Ilia V; Tropea, Cameron

    2015-09-01

    In this study melting of irregular ice crystals was observed in an acoustic levitator. The evolution of the particle shape is captured using a high-speed video system. Several typical phenomena have been discovered: change of the particle shape, appearance of a capillary flow of the melted liquid on the particle surface leading to liquid collection at the particle midsection (where the interface curvature is smallest), and appearance of sharp cusps at the particle tips. No such phenomena can be observed during melting of spherical particles. An approximate theoretical model is developed which accounts for the main physical phenomena associated with melting of an irregular particle. The agreement between the theoretical predictions for the melting time, for the evolution of the particle shape, and the corresponding experimental data is rather good.

  10. Spherical plasmoids formed upon the combustion and explosion of nanostructured hydrated silicon

    Science.gov (United States)

    Lazarouk, S. K.; Dolbik, A. V.; Labunov, V. A.; Borisenko, V. E.

    2007-02-01

    The kinetics of the combustion and explosion of nanostructured hydrated porous silicon has been analyzed in a duration range from 100 μs to 1 s. It has been shown that the presence of hydrogen in silicon nanostructures increases the energy yield of oxidation processes leading to the formation of spherical plasmoids with a size of 0.1-0.8 m. Buoyancy in them can be compensated by the weight of the material particles formed inside and this compensation leads to a change in the velocity of plasmoids from 0.5 m/s to zero in the process of their cooling. It is hypothesized that a ball lightning appears due to the combustion and explosion of nanostructured hydrated silicon in spherical plasmoids.

  11. Cylindrical and Spherical Active Coated Nanoparticles as Nanoantennas: Active nanoparticles as nanoantennas

    DEFF Research Database (Denmark)

    Arslanagic, Samel; Ziolkowski, Richard W.

    2017-01-01

    In this article, we review the fundamental properties of several spherical and cylindrical, passive, and active coated nanoparticles (CNPs) with an emphasis on their potential for nanoantenna and nanoamplifier synthesis. For the spherical geometries, the nanoparticles are excited by an electric...... Hertzian dipole (EHD), which represents, e.g., a stimulated atom or molecule. The cylindrical nanoparticles are excited by a magnetic line source (MLS). In the active cases, gain is added to the core region of the particle. For simplicity, it is represented by a canonical, frequency-independent gain model....... We demonstrate that specific CNPs can be designed to be resonant and well matched to their respective excitation sources. With active cores, these designs can lead to extremely large total radiated powers. For both configurations, insights into the effects of the nanoparticle material composition...

  12. Acoustic manipulation of active spherical carriers: Generation of negative radiation force

    Energy Technology Data Exchange (ETDEWEB)

    Rajabi, Majid, E-mail: majid_rajabi@iust.ac.ir; Mojahed, Alireza

    2016-09-15

    This paper examines theoretically a novel mechanism of generating negative (pulling) radiation force for acoustic manipulation of spherical carriers equipped with piezoelectric actuators in its inner surface. In this mechanism, the spherical particle is handled by common plane progressive monochromatic acoustic waves instead of zero-/higher- order Bessel beams or standing waves field. The handling strategy is based on applying a spatially uniform harmonic electrical voltage at the piezoelectric actuator with the same frequency of handling acoustic waves, in order to change the radiation force effect from repulsive (away from source) to attractive (toward source). This study may be considered as a start point for development of contact-free precise handling and entrapment technology of active carriers which are essential in many engineering and medicine applications.

  13. Relativistic Mechanics in Gravitational Fields Exterior to Rotating Homogeneous Mass Distributions within Spherical Geometry

    Directory of Open Access Journals (Sweden)

    Chifu E. N.

    2009-07-01

    Full Text Available General Relativistic metric tensors for gravitational fields exterior to homogeneous spherical mass distributions rotating with constant angular velocity about a fixed di- ameter are constructed. The coeffcients of affine connection for the gravitational field are used to derive equations of motion for test particles. The laws of conservation of energy and angular momentum are deduced using the generalized Lagrangian. The law of conservation of angular momentum is found to be equal to that in Schwarzschild’s gravitational field. The planetary equation of motion and the equation of motion for a photon in the vicinity of the rotating spherical mass distribution have rotational terms not found in Schwarzschild’s field.

  14. Design of spherical electron gun for ultra high frequency, CW power inductive output tube

    Energy Technology Data Exchange (ETDEWEB)

    Kaushik, Meenu, E-mail: mkceeri@gmail.com; Joshi, L. M., E-mail: lmj1953@gmail.com [Microwave Tubes Division, CSIR-Central Electronics Engineering Research Institute (CEERI), Pilani, Rajasthan (India); Academy of Scientific and Innovative Research (AcSIR), New Delhi (India)

    2016-03-09

    Inductive Output Tube (IOT) is an amplifier that usually operates in UHF range. It is an electron tube whose basic structure is similar to conventional vacuum devices. This device is widely used in broadcast applications but is now being explored for scientific applications also specifically, particle accelerators and fusion plasma heating purposes. The paper describes the design approach of a spherical gridded electron gun of a 500 MHz, 100 kW CW power IOT. The electron gun structure has been simulated and optimized for operating voltage and current of 40kV and 3.5 A respectively. The electromagnetic analysis of this spherical electron gun has been carried out in CST and TRAK codes.

  15. Properties of Mechanically Alloyed W-Ti Materials with Dual Phase Particle Dispersion

    Directory of Open Access Journals (Sweden)

    František Lukáč

    2016-12-01

    Full Text Available W alloys are currently widely studied materials for their potential application in future fusion reactors. In the presented study, we report on the preparation and properties of mechanically alloyed W-Ti powders compacted by pulsed electric current sintering. Four different powder compositions of W-(3%–7%Ti with Hf or HfC were prepared. The alloys’ structure contains only high-melting-point phases, namely the W-Ti matrix, complex carbide (Ti,W,HfC and HfO2 particle dispersion; Ti in the form of a separate phase is not present. The bending strength of the alloys depends on the amount of Ti added. The addition of 3 wt. % Ti led to an increase whereas 7 wt. % Ti led to a major decrease in strength when compared to unalloyed tungsten sintered at similar conditions. The addition of Ti significantly lowered the room-temperature thermal conductivity of all prepared materials. However, unlike pure tungsten, the conductivity of the prepared alloys increased with the temperature. Thus, the thermal conductivity of the alloys at 1300 °C approached the value of the unalloyed tungsten.

  16. Spherical Location Problems with Restricted Regions and Polygonal Barriers

    OpenAIRE

    Dedigama Dewage, Mangalika Jayasundara

    2005-01-01

    This thesis investigates the constrained form of the spherical Minimax location problem and the spherical Weber location problem. Specifically, we consider the problem of locating a new facility on the surface of the unit sphere in the presence of convex spherical polygonal restricted regions and forbidden regions such that the maximum weighted distance from the new facility on the surface of the unit sphere to m existing facilities is minimized and the sum of the weighted distance from the n...

  17. Regularised reconstruction of sound fields with a spherical microphone array

    DEFF Research Database (Denmark)

    Granados Corsellas, Alba; Jacobsen, Finn; Fernandez Grande, Efren

    2013-01-01

    Spherical near field acoustic holography with microphones mounted on a rigid spherical surface is used to reconstruct the incident sound field. However, reconstruction outside the sphere is an ill-posed inverse problem, and since this is very sensitive to the measurement noise, straightforward...... become apparent. Hence, a number of regularisation methods, including truncated singular value decomposition, standard Tikhonov, constrained Tikhonov, iterative Tikhonov, Landweber and Rutishauser, have been adapted for spherical near field acoustic holography. The accuracy of the methods is examined...

  18. Geometric inequalities in spherically symmetric spacetimes

    Science.gov (United States)

    Csukás, Károly Z.

    2017-07-01

    In geometric inequalities ADM mass plays more fundamental role than the concept of quasi-local mass. This paper is to demonstrate that using the quasi-local mass some new insights can be acquired. In spherically symmetric spacetimes the Misner-Sharp mass and the concept of the Kodama vector field provides an ideal setting to the investigations of geometric inequalities. We applying the proposed new techniques to investigate the spacetimes containing black hole or cosmological horizons but we shall also apply them in context of normal bodies. Most of the previous investigations applied only the quasi-local charges and the area. Our main point is to include the quasi-local mass in the corresponding geometrical inequalities. This way we recover some known relations but new inequalities are also derived.

  19. Stability of Spherical Vesicles in Electric Fields

    Science.gov (United States)

    2010-01-01

    The stability of spherical vesicles in alternating (ac) electric fields is studied theoretically for asymmetric conductivity conditions across their membranes. The vesicle deformation is obtained from a balance between the curvature elastic energies and the work done by the Maxwell stresses. The present theory describes and clarifies the mechanisms for the four types of morphological transitions observed experimentally on vesicles exposed to ac fields in the frequency range from 500 to 2 × 107 Hz. The displacement currents across the membranes redirect the electric fields toward the membrane normal to accumulate electric charges by the Maxwell−Wagner mechanism. These accumulated electric charges provide the underlying molecular mechanism for the morphological transitions of vesicles as observed on the micrometer scale. PMID:20575588

  20. Spherically-Convergent, Advanced-Fuel Systems

    Science.gov (United States)

    Barnes, D. C.; Nebel, R. A.; Schauer, M. M.; Umstadter, K. R.

    1998-11-01

    Combining nonneutral electron confinement with spherical ion convergence leads to a cm sized reactor volume with high power density.(R. A. Nebel and D. C. Barnes, Fusion Technol.), to appear (1998); D. C. Barnes and R. A. Nebel, Phys. of Plasmas 5, 2498 (1998). This concept is being investigated experimentally,(D. C. Barnes, T. B. Mitchell, and M. M. Schauer, Phys. Plasmas) 4, 1745 (1997). and results will be reported. We argue that D-D operation of such a system offers all the advantages of aneutronic fusion cycles. In particular, no breeding or large tritium inventory is required, and material problems seem tractable based on previous LWR experience. In addition the extremely small unit size leads to a massively modular system which is easily maintained and repaired, suggesting a very high availability. It may also be possible to operate such a system with low or aneutronic fuels. Preliminary work in this direction will be presented.

  1. Simple spherical ablative-implosion model

    Energy Technology Data Exchange (ETDEWEB)

    Mayer, F.J.; Steele, J.T.; Larsen, J.T.

    1980-06-23

    A simple model of the ablative implosion of a high-aspect-ratio (shell radius to shell thickness ratio) spherical shell is described. The model is similar in spirit to Rosenbluth's snowplow model. The scaling of the implosion time was determined in terms of the ablation pressure and the shell parameters such as diameter, wall thickness, and shell density, and compared these to complete hydrodynamic code calculations. The energy transfer efficiency from ablation pressure to shell implosion kinetic energy was examined and found to be very efficient. It may be possible to attach a simple heat-transport calculation to our implosion model to describe the laser-driven ablation-implosion process. The model may be useful for determining other energy driven (e.g., ion beam) implosion scaling.

  2. Bijels stabilized using rod-like particles.

    Science.gov (United States)

    Hijnen, Niek; Cai, Dongyu; Clegg, Paul S

    2015-06-14

    Bicontinuous interfacially jammed emulsion gels, in short 'bijels', rely on a trapped layer of colloidal particles for their stability. These structures have traditionally been created using spherical colloidal particles. Here we show for the first time the use of rod-shape particles to stabilize bijels. We show that domain size decreases more rapidly with particle concentration in the case of rods compared to spheres. Large-scale analysis and detailed examination of images show that the packing fraction of rods is much higher than expected, in part, due to the role of 'flippers'.

  3. Effect of the particle shape on the particle dynamics in a spheronization process

    Science.gov (United States)

    Weis, Dominik; Niesing, Maria; Thommes, Markus; Antonyuk, Sergiy

    2017-06-01

    Spherical granules with a narrow size distribution are widely used in many pharmaceutical applications. Extrusion-spheronization is a well-established process to produce such pharmaceutical pellets. The cylindrical extrudates from the extrusion step are rounded in the spheronizer. The formation mechanisms inside of a spheronizer depend strongly on the particle dynamics. To describe the complex particle flow and interactions, the Discrete Element Method can be used. In our previous works the spherical particles during the last part of the spheronization process were studied. Since the pellets have a cylindrical shape at the beginning and undergo different stages of deformation during the rounding process, the objective of this study was the description of the influence of the particle shape on the particle dynamics. To predict the interactions of the pellets, their dominant plastic behaviour was described with an appropriate contact model and the material parameters were calibrated with compression and impact tests.

  4. Spherical microwave confinement and ball lightning

    Science.gov (United States)

    Robinson, William Richard

    This dissertation presents the results of research done on unconventional energy technologies from 1995 to 2009. The present civilization depends on an infrastructure that was constructed and is maintained almost entirely using concentrated fuels and ores, both of which will run out. Diffuse renewable energy sources rely on this same infrastructure, and hence face the same limitations. I first examined sonoluminescence directed toward fusion, but demonstrated theoretically that this is impossible. I next studied Low Energy Nuclear Reactions and developed methods for improving results, although these have not been implemented. In 2000, I began Spherical Microwave Confinement (SMC), which confines and heats plasma with microwaves in a spherical chamber. The reactor was designed and built to provide the data needed to investigate the possibility of achieving fusion conditions with microwave confinement. A second objective was to attempt to create ball lightning (BL). The reactor featured 20 magnetrons, which were driven by a capacitor bank and operated in a 0.2 s pulse mode at 2.45 GHz. These provided 20 kW to an icosahedral array of 20 antennas. Video of plasmas led to a redesign of the antennas to provide better coupling of the microwaves to the plasma. A second improvement was a grid at the base of the antennas, which provided corona electrons and an electric field to aid quick formation of plasmas. Although fusion conditions were never achieved and ball lightning not observed, experience gained from operating this basic, affordable system has been incorporated in a more sophisticated reactor design intended for future research. This would use magnets that were originally planned. The cusp geometry of the magnetic fields is suitable for electron cyclotron resonance in the same type of closed surface that in existing reactors has generated high-temperature plasmas. Should ball lightning be created, it could be a practical power source with nearly ideal

  5. Dynamical systems and spherically symmetric cosmological models

    Science.gov (United States)

    He, Yanjing

    2006-06-01

    In this thesis we present a study of the timelike self-similar spherically symmetric cosmological models with two scalar fields with exponential potentials. We first define precisely the timelike self-similar spherically symmetric (TSS) spacetimes. We write the TSS metric in a conformally isometric form in a coordinate system adapted to the geometry of the spacetime manifold. In this coordinate system, both the metric functions of the TSS spacetimes and the potential functions of the scalar fields can be simplified to four undetermined functions of a single coordinate. As a result, the Einstein field equations reduce to an autonomous system of first-order ODEs and polynomial constraints in terms of these undetermined functions. By introducing new bounded variables as well as a new independent variable and solving the constraints, we are able to apply the theory of dynamical systems to study the properties of the TSS solutions. By finding invariant sets and associated monotonic functions, by applying the LaSalle Invariance Principle and the Monotonicity Principle, by applying the [straight phi] t -connected property of a limit set, and using other theorems, we prove that all of the TSS trajectories are heteroclinic trajectories. In addition, we conduct numerical simulations to confirm and support the qualitative analysis. We obtain all possible types of TSS solutions, by analyzing the qualitative behavior of the original system of ODES from those of the reduced one. We obtain asymptotic expressions for the TSS solutions (e.g., the asymptotic expressions for the metric functions, the source functions and the Ricci scalar). In particular, self-similar flat Friedmann-Robertson-Walker spacetimes are examined in order to obtain insights into the issues related to the null surface in general TSS spacetimes in these coordinates. A discussion of the divergence of the spacetime Ricci scalar and the possible extension of the TSS solutions across the null boundary is presented

  6. Gas-solute dispersivity ratio in granular porous media as related to particle size distribution and particle shape

    DEFF Research Database (Denmark)

    Pugliese, Lorenzo; Poulsen, Tjalfe; Straface, Salvatore

    2013-01-01

    different, granular porous materials were used: (1) crushed granite (very angular particles), (2) gravel (particles of intermediate roundness) and (3) Leca® (almost spherical particles). For each material, 21 different particle size fractions were used. Gas and solute dispersion coefficients were determined...... by fitting the advection-dispersion equation to the measured breakthrough curves and in turn used to calculate gas and solute dispersivities as a function of mean particle size (Dm) and particle size range (R) for the 63 particle size fractions considered. The results show that solute and gas dispersivities...

  7. A multiball read-out for the spherical proportional counter

    Science.gov (United States)

    Giganon, A.; Giomataris, I.; Gros, M.; Katsioulas, I.; Navick, X. F.; Tsiledakis, G.; Savvidis, I.; Dastgheibi-Fard, A.; Brossard, A.

    2017-12-01

    We present a novel concept of proportional gas amplification for the read-out of the spherical proportional counter. The standard single-ball read-out presents limitations for large diameter spherical detectors and high-pressure operations. We have developed a multi-ball read-out system which consists of several balls placed at a fixed distance from the center of the spherical vessel. Such a module can tune the volume electric field at the desired value and can also provide detector segmentation with individual ball read-out. In the latter case, the large volume of the vessel becomes a spherical time projection chamber with 3D capabilities.

  8. Investigation of spherical and concentric mechanism of compound droplets

    Directory of Open Access Journals (Sweden)

    Meifang Liu

    2016-07-01

    Full Text Available Polymer shells with high sphericity and uniform wall thickness are always needed in the inertial confined fusion (ICF experiments. Driven by the need to control the shape of water-in-oil (W1/O compound droplets, the effects of the density matching level, the interfacial tension and the rotation speed of the continuing fluid field on the sphericity and wall thickness uniformity of the resulting polymer shells were investigated and the spherical and concentric mechanisms were also discussed. The centering of W1/O compound droplets, the location and movement of W1/O compound droplets in the external phase (W2 were significantly affected by the density matching level of the key stage and the rotation speed of the continuing fluid field. Therefore, by optimizing the density matching level and rotation speed, the batch yield of polystyrene (PS shells with high sphericity and uniform wall thickness increased. Moreover, the sphericity also increased by raising the oil/water (O/W2 interfacial tension, which drove a droplet to be spherical. The experimental results show that the spherical driving force is from the interfacial tension affected by the two relative phases, while the concentric driving force, as a resultant force, is not only affected by the three phases, but also by the continuing fluid field. The understanding of spherical and concentric mechanism can provide some guidance for preparing polymer shells with high sphericity and uniform wall thickness.

  9. Low-Q Electrically Small Spherical Magnetic Dipole Antennas

    DEFF Research Database (Denmark)

    Kim, Oleksiy S.

    2010-01-01

    Three novel electrically small antenna configurations radiating a TE10 spherical mode corresponding to a magnetic dipole are presented and investigated: multiarm spherical helix (MSH) antenna, spherical split ring resonator (S-SRR) antenna, and spherical split ring (SSR) antenna. All three antennas...... are self-resonant, with the input resistance tuned to 50 ohms by an excitation curved dipole/monopole. A prototype of the SSR antenna has been fabricated and measured, yielding results that are consistent with the numerical simulations. Radiation quality factors (Q) of these electrically small antennas (in...

  10. Polygamous particles

    OpenAIRE

    Wu, Kun-Ta; Feng, Lang; Sha, Ruojie; Dreyfus, Rémi; Grosberg, Alexander Y.; Seeman, Nadrian C.; Chaikin, Paul M.

    2012-01-01

    DNA is increasingly used as an important tool in programming the self-assembly of micrometer- and nanometer-scale particles. This is largely due to the highly specific thermoreversible interaction of cDNA strands, which, when placed on different particles, have been used to bind precise pairs in aggregates and crystals. However, DNA functionalized particles will only reach their true potential for particle assembly when each particle can address and bind to many different kinds of particles. ...

  11. Higher spins tunneling from a time dependent and spherically symmetric black hole

    Energy Technology Data Exchange (ETDEWEB)

    Siahaan, Haryanto M. [Parahyangan Catholic University, Physics Department, Bandung (Indonesia)

    2016-03-15

    The discussions of Hawking radiation via tunneling method have been performed extensively in the case of scalar particles. Moreover, there are also several works in discussing the tunneling method for Hawking radiation by using higher spins, e.g. neutrino, photon, and gravitino, in the background of static black holes. Interestingly, it is found that the Hawking temperature for static black holes using the higher spins particles has no difference compared to the one computed using scalars. In this paper, we study the Hawking radiation for a spherically symmetric and time dependent black holes using the tunneling of Dirac particles, photon, and gravitino. We find that the obtained Hawking temperature is similar to the one derived in the tunneling method by using scalars. (orig.)

  12. Synthesis of Spherical Bi2WO6 Nanoparticles by a Hydrothermal Route and Their Photocatalytic Properties

    Directory of Open Access Journals (Sweden)

    B. Wang

    2015-01-01

    Full Text Available Spherical Bi2WO6 nanoparticles were synthesized by a hydrothermal route. SEM observation shows that the size of the particles ranges from 60 to 120 nm and the average particle size is ~85 nm. TEM investigation shows that the particles are made up of subgrains with size of 5–10 nm. The bandgap energy of the particles is measured to be 2.93 eV by ultraviolet-visible diffuse reflectance spectroscopy. RhB was chosen as the target pollutant to evaluate the photocatalytic activity of the particles under irradiation of simulated sunlight, revealing that they exhibit an obvious photocatalytic activity. The effects of ethanol, KI, and BQ on the photocatalytic efficiency of Bi2WO6 particles towards the RhB degradation were investigated. It is observed that ethanol has no effect on the photocatalytic degradation of RhB, whereas KI and BQ exhibit a substantial suppression of RhB degradation. No hydroxyl (•OH is found, by the photoluminescence technique using terephthalic acid as a probe molecule, to be produced over the irradiated Bi2WO6 particles. Based on the experimental results, photoexcited hole (h+ and superoxide (•O2- are suggested to be the two main active species responsible for the dye degradation, while •OH plays a negligible role in the photocatalysis.

  13. A novel process route for the production of spherical SLS polymer powders

    Science.gov (United States)

    Schmidt, Jochen; Sachs, Marius; Blümel, Christina; Winzer, Bettina; Toni, Franziska; Wirth, Karl-Ernst; Peukert, Wolfgang

    2015-05-01

    Currently, rapid prototyping gradually is transferred to additive manufacturing opening new applications. Especially selective laser sintering (SLS) is promising. One drawback is the limited choice of polymer materials available as optimized powders. Powders produced by cryogenic grinding show poor powder flowability resulting in poor device quality. Within this account we present a novel process route for the production of spherical polymer micron-sized particles of good flowability. The feasibility of the process chain is demonstrated for polystyrene e. In a first step polymer microparticles are produced by a wet grinding method. By this approach the mean particle size and the particle size distribution can be tuned between a few microns and several 10 microns. The applicability of this method will be discussed for different polymers and the dependencies of product particle size distribution on stressing conditions and process temperature will be outlined. The comminution products consist of microparticles of irregular shape and poor powder flowability. An improvement of flowability of the ground particles is achieved by changing their shape: they are rounded using a heated downer reactor. The influence of temperature profile and residence time on the product properties will be addressed applying a viscous-flow sintering model. To further improve the flowability of the cohesive spherical polymer particles nanoparticles are adhered onto the microparticles' surface. The improvement of flowability is remarkable: rounded and dry-coated powders exhibit a strongly reduced tensile strength as compared to the comminution product. The improved polymer powders obtained by the process route proposed open new possibilities in SLS processing including the usage of much smaller polymer beads.

  14. A novel process route for the production of spherical SLS polymer powders

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, Jochen; Sachs, Marius; Blümel, Christina; Winzer, Bettina; Toni, Franziska; Wirth, Karl-Ernst; Peukert, Wolfgang [Institute of Particle Technology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Cauerstraße 4, D-91058 Erlangen (Germany)

    2015-05-22

    Currently, rapid prototyping gradually is transferred to additive manufacturing opening new applications. Especially selective laser sintering (SLS) is promising. One drawback is the limited choice of polymer materials available as optimized powders. Powders produced by cryogenic grinding show poor powder flowability resulting in poor device quality. Within this account we present a novel process route for the production of spherical polymer micron-sized particles of good flowability. The feasibility of the process chain is demonstrated for polystyrene e. In a first step polymer microparticles are produced by a wet grinding method. By this approach the mean particle size and the particle size distribution can be tuned between a few microns and several 10 microns. The applicability of this method will be discussed for different polymers and the dependencies of product particle size distribution on stressing conditions and process temperature will be outlined. The comminution products consist of microparticles of irregular shape and poor powder flowability. An improvement of flowability of the ground particles is achieved by changing their shape: they are rounded using a heated downer reactor. The influence of temperature profile and residence time on the product properties will be addressed applying a viscous-flow sintering model. To further improve the flowability of the cohesive spherical polymer particles nanoparticles are adhered onto the microparticles’ surface. The improvement of flowability is remarkable: rounded and dry-coated powders exhibit a strongly reduced tensile strength as compared to the comminution product. The improved polymer powders obtained by the process route proposed open new possibilities in SLS processing including the usage of much smaller polymer beads.

  15. Reactive Hydrodynamics in Rotating Spherical and Cylindrical Geometry

    Science.gov (United States)

    Sohrab, Siavash H.

    1997-01-01

    In turbulent spray combustion among many complex interactions between local flow structures called turbulent eddies and droplets are those associated with rotation of droplets. In general, for a complete statistical description of turbulent sprays, consideration of at least four degrees of freedom respectively associated with translational, rotational, vibrational (pulsational), and internal motions of the droplet are needed. Clearly the interactions between all degrees of freedom of the droplets and those for the gaseous background field will be exceedingly complex. For example, one type of interaction between the translational and the rotational velocity of droplets results in droplet helicity, H(d) = w(d).v(d), the significance of which in turbulent spray combustion is yet to be recognized. The role of droplet rotation in turbulent spray combustion modeling and its impact on the evaporation of liquid fuel droplets was recently investigated. Also, the impact of rotation on combustion of solid particles such as is encountered in pulverized coal combustion has been emphasized. The problem of viscous flow around a rotating sphere discussed above also occurs in other areas of physical sciences such as astrophysics and geophysics. Consequently, the subject has been addressed in many classical as well as more recent investigations. According to these investigations, the rotation of a rigid sphere in an otherwise quiescent, unconfined environment results in the motion of the fluid towards the poles. The polar flows from the northern and southern hemispheres move along helical trajectories towards the equatorial plane. Eventually, the polar flows collide at the equatorial plane, thus producing a sheet of rotating fluid that is radially ejected outward on this plane. Therefore, a droplet induces a strained flow field as a result of its rotation. Since the spatial extent of equatorial jets could easily exceed many droplet diameters, interactions between neighboring

  16. Effect of particle shape on mechanical behaviors of rocks: a numerical study using clumped particle model.

    Science.gov (United States)

    Rong, Guan; Liu, Guang; Hou, Di; Zhou, Chuang-Bing

    2013-01-01

    Since rocks are aggregates of mineral particles, the effect of mineral microstructure on macroscopic mechanical behaviors of rocks is inneglectable. Rock samples of four different particle shapes are established in this study based on clumped particle model, and a sphericity index is used to quantify particle shape. Model parameters for simulation in PFC are obtained by triaxial compression test of quartz sandstone, and simulation of triaxial compression test is then conducted on four rock samples with different particle shapes. It is seen from the results that stress thresholds of rock samples such as crack initiation stress, crack damage stress, and peak stress decrease with the increasing of the sphericity index. The increase of sphericity leads to a drop of elastic modulus and a rise in Poisson ratio, while the decreasing sphericity usually results in the increase of cohesion and internal friction angle. Based on volume change of rock samples during simulation of triaxial compression test, variation of dilation angle with plastic strain is also studied.

  17. Studies on hollow spherical aluminum silicate cluster. Synthesis of environment friendly materials; Chuku kyujo aluminium keisan`en cluster ni kansuru kenkyu

    Energy Technology Data Exchange (ETDEWEB)

    Ohashi, F.; Maeda, M.; Suzuki, M.; Watamura, S. [National Industrial Research Institute of Nagoya,Nagoya (Japan)

    1999-01-25

    Synthesis of microfine particles of nanometer size, their surface adulteration and control of microstructure take an important position in different areas, such as electronics, chemical, machine and metal industries. However, reports on the established methods for synthesizing hollow spherical particles of nanometer size, which may be applied to micro capsules, cannot be found except for fullerene composed of carbon. This paper introduces a new method for synthesizing hollow spherical amorphous aluminum silicate cluster called allophane as an earth environmental material, and the derived properties of allophane. (translated by NEDO)

  18. Coated nano-particle jamming of quantum emitters

    DEFF Research Database (Denmark)

    Arslanagic, Samel; Ziolkowski, Richard W.

    2012-01-01

    Spherical active coated nano-particles are examined analytically and numerically in the presence of one, two or four quantum emitters (electric Hertzian dipoles). The ability of the coated nano-particle to effectively cloak the emitters to a far-field observer is reported. This offers...

  19. Influence of Torrefaction on Single Particle Combustion of Wood

    DEFF Research Database (Denmark)

    Lu, Zhimin; Jian, Jie; Jensen, Peter Arendt

    2016-01-01

    This study focuses on the influence of torrefaction on the char reactivity, char yield, and combustion time of 3-5 mm spherical wood particles in a single particle combustion reactor (SPC) operating at a nominal temperature of 1231 °C. The devolatilization times were reduced and the char burnout...

  20. Mono-disperse spherical Cu-Zn powder fabricated via the low wettability of liquid/solid interface

    Science.gov (United States)

    Lei, Chenglong; Huang, Haifu; Cheng, Zhenzhi; Tang, Shaolong; Du, Youwei

    2015-12-01

    Spherical Cu-Zn alloy powders were fabricated by combining the surface tension of a molten metal with the de-wetting of a metal droplet on a graphite surface. The effect that the gas pressure had on the surface morphology and composition was studied. The Zn concentration can be maintained at 20.18 wt.%, 15.5 wt.% and 12.08 wt.% using 0.22 MPa, 0.10 MPa, and 0.04 MPa, respectively, from a commercially available Cu-38 wt.%Zn raw material. The gas pressure was adjusted to control the surface volatility of Zn without affecting the spherical morphology, and higher gas pressure yielded less volatile Zn. The Cu-Zn alloy powders were perfectly spherical, even at a negative pressure of 0.04 MPa. The spherical Cu-Zn alloy particles hardly changed and were fully dense up to Cu-50 wt.%Zn, which allowed high-quality spherical Cu-Zn alloy powders to potentially serve a large composition range.

  1. Enhanced dissolution rate of felodipine using spherical agglomeration with Inutec SP1 by quasi emulsion solvent diffusion method

    Science.gov (United States)

    Tapas, A.R.; Kawtikwar, P.S.; Sakarkar, D.M.

    2009-01-01

    Felodipine is a second generation calcium channel blocker widely used as antihypertensive and antianginal drug which belongs to BCS class II category. Hence, its low water solubility limits the pharmacological effect. The aim of this study was to improve the dissolution rate of felodipine using spherical agglomeration technique with acetone, water and dichloromethane as good solvent, poor solvent and bridging liquid, respectively. The quasi emulsion solvent diffusion technique was used as a method for spherical agglomeration. Inutec SP1 was used as an emulsion stabilizer and as hydrophilic polymer in agglomeration process. The FTIR and DSC results showed no change in the drug after crystallization process. PXRD studies showed sharp peaks in the diffractograms of spherical agglomerates with minor reduction in height of the peaks. The particle size of spherical agglomerates (FI-2) was about 134.33 ± 13.57 µm, n=3 and the dissolution efficiency of felodipine up to 120 min increased to about 4-fold in phosphate buffer containing 1.8% Tween 80 (pH 6.8). Spherical agglomerates showed enhanced solubility compared to untreated powder possibly due to the partial conversion to amorphous form. PMID:21589802

  2. Particle diffusion in complex nanoscale pore networks

    DEFF Research Database (Denmark)

    Müter, Dirk; Sørensen, Henning Osholm; Bock, H.

    2015-01-01

    We studied the diffusion of particles in the highly irregular pore networks of chalk, a very fine-grained rock, by combining three-dimensional X-ray imaging and dissipative particle dynamics (DPD) simulations. X-ray imaging data were collected at 25 nm voxel dimension for two chalk samples...... with very different porosities (4% and 26%). The three-dimensional pore systems derived from the tomograms were imported into DPD simulations and filled with spherical particles of variable diameter and with an optional attractive interaction to the pore surfaces. We found that diffusion significantly...... decreased to as much as 60% when particle size increased from 1% to 35% of the average pore diameter. When particles were attracted to the pore surfaces, even very small particles, diffusion was drastically inhibited, by as much as a factor of 100. Thus, the size of particles and their interaction...

  3. Acoustic radiation force control: Pulsating spherical carriers.

    Science.gov (United States)

    Rajabi, Majid; Mojahed, Alireza

    2018-02-01

    The interaction between harmonic plane progressive acoustic beams and a pulsating spherical radiator is studied. The acoustic radiation force function exerted on the spherical body is derived as a function of the incident wave pressure and the monopole vibration characteristics (i.e., amplitude and phase) of the body. Two distinct strategies are presented in order to alter the radiation force effects (i.e., pushing and pulling states) by changing its magnitude and direction. In the first strategy, an incident wave field with known amplitude and phase is considered. It is analytically shown that the zero- radiation force state (i.e., radiation force function cancellation) is achievable for specific pulsation characteristics belong to a frequency-dependent straight line equation in the plane of real-imaginary components (i.e., Nyquist Plane) of prescribed surface displacement. It is illustrated that these characteristic lines divide the mentioned displacement plane into two regions of positive (i.e., pushing) and negative (i.e., pulling) radiation forces. In the second strategy, the zero, negative and positive states of radiation force are obtained through adjusting the incident wave field characteristics (i.e., amplitude and phase) which insonifies the radiator with prescribed pulsation characteristics. It is proved that zero radiation force state occurs for incident wave pressure characteristics belong to specific frequency-dependent circles in Nyquist plane of incident wave pressure. These characteristic circles divide the Nyquist plane into two distinct regions corresponding to positive (out of circles) and negative (in the circles) values of radiation force function. It is analytically shown that the maximum amplitude of negative radiation force is exactly equal to the amplitude of the (positive) radiation force exerted upon the sphere in the passive state, by the same incident field. The developed concepts are much more deepened by considering the required

  4. Characterizing Student Mathematics Teachers' Levels of Understanding in Spherical Geometry

    Science.gov (United States)

    Guven, Bulent; Baki, Adnan

    2010-01-01

    This article presents an exploratory study aimed at the identification of students' levels of understanding in spherical geometry as van Hiele did for Euclidean geometry. To do this, we developed and implemented a spherical geometry course for student mathematics teachers. Six structured, "task-based interviews" were held with eight student…

  5. Cylindrical and spherical dust-acoustic wave modulations in dusty ...

    Indian Academy of Sciences (India)

    The nonlinear wave modulation of planar and non-planar (cylindrical and spherical) dust-acoustic waves (DAW) propagating in dusty plasmas, in the presence of non-extensive distributions for ions and electrons is investigated. By employing multiple scales technique, a cylindrically and spherically modified nonlinear ...

  6. Effect of the spherical Earth on a simple pendulum

    OpenAIRE

    Burko, Lior M.

    2003-01-01

    We consider the period of a simple pendulum in the gravitational field of the spherical Earth. Effectively, gravity is enhanced compared with the often used flat Earth approximation, such that the period of the pendulum is shortened. We discuss the flat Earth approximation, and show when the corrections due to the spherical Earth may be of interest.

  7. Spherical dust acoustic solitary waves with two temperature ions

    CERN Document Server

    Eslami, Esmaeil

    2014-01-01

    The nonlinear dust acoustic waves in unmagnetized dusty plasma which consists of two temperature Boltzmann distributed ions and Boltzmann distributed electrons in spherical dimension investigated and obtained spherical Kadomtsev Petviashvili (SKP) equation and shown that the dust acoustic solitary wave can exist in the SKP equation.

  8. Rapid Prototyping of Electrically Small Spherical Wire Antennas

    DEFF Research Database (Denmark)

    Kim, Oleksiy S.

    2014-01-01

    It is shown how modern rapid prototyping technologies can be applied for quick and inexpensive, but still accurate, fabrication of electrically small wire antennas. A well known folded spherical helix antenna and a novel spherical zigzag antenna have been fabricated and tested, exhibiting the imp...

  9. demonstrating close-packing of atoms using spherical bubble gums

    African Journals Online (AJOL)

    Admin

    ABSTRACT: In this paper, the use of spherical bubble gums (Gum Balls) to demonstrate the close-packing of atoms and ions is presented. Spherical bubble gums having distinctive colours were used to illustrate the different layers in variety of crystalline packing and the formation of tetrahedral and octahedral holes.

  10. Development of a spherical aerial vehicle for urban search

    Science.gov (United States)

    Hou, Kang; Sun, Hanxu; Jia, Qingxuan; Zhang, Yanheng

    2014-06-01

    With the ability to provide close surveillance in narrow space or urban areas, spherical aerial vehicles have been of great interest to many scholars and researchers. The spherical aerial vehicle offers substantial design advantages over the conventional small aerial vehicles. As a kind of small aerial vehicles, spherical aerial vehicle is presented in this paper. Firstly, the unique structure of spherical aerial vehicle is presented in detail. And then as the key component of the spherical aerial vehicle, the meshed spherical shell is analyzed. The shell is made of carbon fiber and is used to protect the inner devices, so the deformation of the shell is analyzed and simulated. Then the experimental results verify the above analysis and the composite carbon fiber material makes the mesh spherical shell small deformation. Considering the whole vehicle has a shell outside, the lift affect of the meshed spherical shell is analyzed. The simulation and experiment results are basically consistent with theoretical analysis, and the impact of the meshed shell has small resistance for the airflow through the sphere.

  11. Some spherical analysis related to the pairs (U (n), Hn)

    Indian Academy of Sciences (India)

    In this paper, we define the normalized spherical transform associated with the generalized Gelfand pair ( U ( p , q ) , H n ) , where H n is the Heisenberg group 2 + 1-dimensional and + = . We show that the normalized spherical transform F ( f ) of a Schwartz function on H n restricted to the spectrum of the Gelfand ...

  12. Calculated scan characteristics of a large spherical reflector antenna

    Science.gov (United States)

    Agrawal, P. K.; Croswell, W. F.; Kauffman, J. F.

    1979-01-01

    A previously published numerical method to calculate the radiation properties of parabolic reflectors has been modified to also include very large spherical reflectors. The method has been verified by comparing the calculated and the measured results for a 120-wavelength spherical reflector.

  13. Cylindrical and spherical dust-acoustic wave modulations in dusty ...

    Indian Academy of Sciences (India)

    Abstract. The nonlinear wave modulation of planar and non-planar (cylindrical and spherical) dust-acoustic waves (DAW) propagating in dusty plasmas, in the presence of non-extensive distribu- tions for ions and electrons is investigated. By employing multiple scales technique, a cylindrically and spherically modified ...

  14. On spherically symmetric singularity-free models in relativistic ...

    Indian Academy of Sciences (India)

    These observations led to the search of spherically symmetric singularity-free cosmo- logical models with a perfect fluid source characterized by isotropic pressure This search resulted in construction of two spherically symmetric singularity-free relativistic cosmo- logical models, describing universes filled with non-adiabatic ...

  15. A Robust Solution of the Spherical Burmester Problem

    DEFF Research Database (Denmark)

    Angeles, Jorge; Bai, Shaoping

    2010-01-01

    The problem of spherical four-bar linkage synthesis is revisited in this paper. The work is aimed at developing a robust synthesis method by taking into account both the formulation and the solution method. In addition, the synthesis of linkages with spherical prismatic joints is considered...

  16. An investigation of embeddings for spherically symmetric ...

    Indian Academy of Sciences (India)

    symmetric spacetimes as they are relevant in astrophysics and cosmology, and we concen- trate on Einstein spaces because of their role in higher-dimensional particle physics, as well as their geometric simplicity. Because the usual method of solving the five-dimensional metric for a chosen four-dimensional space leads to ...

  17. Role of inter-particle force between micro and nano magnetic particles on the stability of magnetorheological fluid

    Directory of Open Access Journals (Sweden)

    Zarana Laherisheth

    2017-02-01

    Full Text Available The concept of phase condensation of larger size particles in a poly-dispersed magnetic fluid (also known as ferrofluid is employed as a tool to investigate the interaction of nanoparticles with micro particles in magnetorheological (MR fluid. Two different shapes iron micron sized particles are used in MR fluid formulation: spherical and flake shaped. The magnetic fluid is used as a base carrier having three different magnetic nanoparticles volume fraction (0.2%, 0.6% and 0.8%. The study suggests that the interaction of magnetic nanoparticles with micron sized particle depends on the geometrical shape of the particle as well as surface roughness. The sedimentation ratio of flake shaped MR fluid increases with nanoparticles volume fractions while for spherical particles it remains virtually constant. The supernatant fluid analysis suggests that, larger sized particle fraction from magnetic fluid are attached to the surface of micron sized flake shape particles, which results in reduction of sliding friction between the particles and small sized fraction clouds around the flake. The atomic force microscopy results suggest that the surface roughness of flake shape particles are nearly 5 times higher than spherical shape particles. The role of these two different interactions is reflected in the sedimentation ratio of MR fluid.

  18. Creep stresses in a spherical shell under steady state temperature

    Science.gov (United States)

    Verma, Gaurav; Rana, Puneet

    2017-10-01

    The paper investigates the problem of creep of a spherical structure under the influence of steady state temperature. The problem of creep in spherical shell is solved by using the concept of generalized strain measures and transition hypothesis given by Seth. The problem has reduced to non-linear differential equation for creep transition. This paper deals with the non-linear behaviour of spherical shell under thermal condition. The spherical shell structures are easily vulnerable to creep, shrinkage and thermal effects; a thorough understanding of their time-dependent behaviour has been fully established. The paper aims to provide thermal creep analysis to enhance the effective design and long life of shells, and a theoretical model is developed for calculating creep stresses and strains in a spherical shell with purpose. Results obtained for the problem are depicted graphically.

  19. Theory and applications of spherical microphone array processing

    CERN Document Server

    Jarrett, Daniel P; Naylor, Patrick A

    2017-01-01

    This book presents the signal processing algorithms that have been developed to process the signals acquired by a spherical microphone array. Spherical microphone arrays can be used to capture the sound field in three dimensions and have received significant interest from researchers and audio engineers. Algorithms for spherical array processing are different to corresponding algorithms already known in the literature of linear and planar arrays because the spherical geometry can be exploited to great beneficial effect. The authors aim to advance the field of spherical array processing by helping those new to the field to study it efficiently and from a single source, as well as by offering a way for more experienced researchers and engineers to consolidate their understanding, adding either or both of breadth and depth. The level of the presentation corresponds to graduate studies at MSc and PhD level. This book begins with a presentation of some of the essential mathematical and physical theory relevant to ...

  20. Spreading widths of giant resonances in spherical nuclei: Damped transient response

    Science.gov (United States)

    Severyukhin, A. P.; Åberg, S.; Arsenyev, N. N.; Nazmitdinov, R. G.

    2017-06-01

    We propose a general approach to describe spreading widths of monopole, dipole, and quadrupole giant resonances in heavy and superheavy spherical nuclei. Our approach is based on the ideas of the random matrix distribution of the coupling between one-phonon and two-phonon states generated in the random-phase approximation. We use the Skyrme interaction SLy4 as our model Hamiltonian to create a single-particle spectrum and to analyze excited states of the doubly magic nuclei 132Sn, 208Pb, and 310126. Our results demonstrate that the approach enables to us to describe a gross structure of the spreading widths of the giant resonances considered.