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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 1 (2000), S. 5-8 
    ISSN: 1292-895X
    Keywords: PACS. 83.70.Fn Granular solids - 45.90.+t Other topics in classical mechanics of discrete systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: In a previous work [#!ref1!#], the flow velocity of a steady two-dimensional granular flow along an inclined wall was investigated. The scaling law for the velocity field was found in good agreement with recent experimental results. The purpose of the present paper is to reformulate in more systematic manner and in a somewhat more general context the equations of mass and momentum conservation for dense granular flow, and also to present some new results with particular emphasis on roughness influence and dynamic dilatancy. Theoretical results are found in good agreement with experiments.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 1 (2000), S. 27-40 
    ISSN: 1292-895X
    Keywords: PACS. 36.20.Ey Conformation (statistics and dynamics) - 61.25.Hq Macromolecular and polymer solutions; polymer melts; swelling - 82.70.Dd Colloids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We present an analytical self-consistent-field (SCF) theory for a neutral polymer brush (a layer of long polymer chains end-grafted to a surface) with annealed excluded volume interactions between the monomer units. This model mimics the reversible adsorption of solute molecules or aggregates, such as small globular proteins or surfactant micelles, on the grafted chains. The equilibrium structural properties of the brush (the brush thickness, the monomer density profile, the distribution of the end segments of the grafted chains) as well as the overall adsorbed amount and the adsorbate density profile are analyzed as a function of the grafting density, the excluded volume parameters and the chemical potential (the concentration) of the adsorbate in the solution. We demonstrate that, when the grafting density is varied, the overall adsorbed amount always exhibits a maximum, whereas the root-mean-square brush thickness either increases monotonically or passes through a (local) minimum. At high grafting densities the chains are loaded by adsorbed aggregates preferentially in the distal region of the brush, whereas in the region proximal to the grafting surface depletion of aggregates occurs and the polymer brush retains an unperturbed structure. Depending on the relative strength of the excluded volume interactions between unloaded and loaded monomers both the degree of loading of the chains and the polymer density profile are either continuous or they exhibit a discontinuity as a function of the distance from the grafting surface. In the latter case intrinsic phase separation occurs in the brush: the dense phase consists of unloaded and weakly extended chains and occupies the region proximal to the surface, whereas a more dilute phase consisting of highly loaded and strongly extended chains forms the periphery of the brush.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 1 (2000), S. 55-59 
    ISSN: 1292-895X
    Keywords: PACS. 81.05.Rm Porous materials; granular materials - 83.70.Fn Granular solids - 46.40.-f Vibrations and mechanical waves
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: In horizontally shaken granular material different types of pattern formation have been reported. We want to deal with the convection instability which has been observed in experiments and which recently has been investigated numerically. Using two dimensional molecular dynamics we show that the convection pattern depends crucially on the inelastic properties of the material. The concept of restitution coefficient provides arguments for the change of the behaviour with varying inelasticity.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 1 (2000), S. 141-152 
    ISSN: 1292-895X
    Keywords: PACS. 82.70.-y Disperse systems - 61.30.Eb Experimental determinations of smectic, nematic, cholesteric, and other structures - 68.10.-m Fluid surfaces and fluid-fluid interfaces
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We study the interplay between thermal undulations and electrostatic interactions for weakly charged surfactant bilayers by measuring the backscattering of light from very dilute lamellar phases of the non-ionic surfactant triethylene glycol monodecyl ether (C10E3) doped with small amounts of the anionic surfactant sodium dodecyl sulphate (SDS), both with and without added electrolyte. Upon charging, the lamellar phases show a transition from undulation to electrostatic stabilization. Non-lamellar structures develop if the molar mixing ratio exceeds . Deviations from ideal swelling, , where is the lamellar repeating distance and the membrane volume fraction, were detected for all lamellar phases. Salt-free lamellar phases with charge densities below , as well as more highly charged lamellar phases at high ionic strength show a universal logarithmic deviation from ideal swelling that was analyzed using theories for undulation stabilized lamellar phases. Deviations from ideal swelling for electrostatically stabilized lamellar phases were analyzed using theories recently developed for undulations in charged lamellar phases. The fits to the various theories yield a value of for the bending modulus of the C10E3 bilayers.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 1 (2000), S. 189-194 
    ISSN: 1292-895X
    Keywords: PACS. 92.40.Lg Soil moisture - 46.50.+a Fracture mechanics, fatigue and cracks - 46.65.+g Random phenomena and media
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Drying induced shrinkage in materials may yield the formation of surface crack patterns. We report on various experimental observations of the geometry of the crack array and the kinetics of crack formation on a model system consisting of a layer of a paste made of clay, sand, and water deposited on a rigid substrate. We investigate in detail the influence of the layer geometry (size and thickness).
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 1 (2000), S. 237-248 
    ISSN: 1292-895X
    Keywords: PACS. 87.16.Dg Membranes, bilayers, and vesicles - 64.75.+g Solubility, segregation, and mixing; phase separation - 82.65.Dp Thermodynamics of surfaces and interfaces
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The effect of rigid inclusions on the phase behavior of a film containing a mixture of lipid molecules is investigated. In the proposed model, the inclusion-induced deformation of the film, and the resulting energy cost are strongly dependent upon the spontaneous curvature of the mixed film. The spontaneous curvature is in turn strongly influenced by the composition of film. This coupling between the film composition and the energy per inclusion leads to a lateral modulation of the composition, which follows the local curvature of the membrane. In particular, it is shown that inclusions may induce a global phase separation in a film which would otherwise be homogeneously mixed. The mixed film is then composed of patches of different average composition, separated by the inclusions. This process may be of relevance to explain some aspects of lipid-protein association in biological membranes.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 1 (2000), S. 265-273 
    ISSN: 1292-895X
    Keywords: PACS. 47.55.Kf Multiphase and particle-laden flows - 83.70.Fn Granular solids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: This paper considers the segregation of a granular mixture in a rotating drum. Extending a recent kinematic model for grain transport on sandpile surfaces to the case of rotating drums, an analysis is presented for radial segregation in the rolling regime, where a thin layer is avalanching down while the rest of the material follows rigid body rotation. We argue that segregation is driven not just by differences in the angle of repose of the species, as has been assumed in earlier investigations, but also by differences in the size and surface properties of the grains. The cases of grains differing only in size (slightly or widely) and only in surface properties are considered, and the predictions are in qualitative agreement with observations. The model yields results inconsistent with the assumptions for more general cases, and we speculate on how this may be corrected.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 1 (2000), S. 341-344 
    ISSN: 1292-895X
    Keywords: PACS. 05.70.Jk Critical point phenomena - 74.80.Bj Granular, melt-textured, and amorphous superconductors; powders
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The dynamics of intermittent granular flow through an orifice at the bottom of a granular bin and the associated clogging due to formation of arches blocking the outlet, is studied numerically in two dimensions. When the hole size is less than the grain diameter, only a single grain is removed from the system so that the system self-organizes to a steady state and the distribution of the grain displacements decays as power laws. On the other hand, when hole sizes are within few times of the grain diameter, the outflow distributions are also observed to follow a power law.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 2 (2000), S. 31-38 
    ISSN: 1292-895X
    Keywords: PACS 82.70.Dd Colloids – 47.20.Bp Buoyancy-driven instability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We present the study of the settling of a colloidal gel in a cell tilted at an angle . In suspensions of non-colloidal particles, the inclination of the sedimentation cell leads to a large enhancement of the settling velocity known as “Boycott effect” well described by the PNK model. We show that the specific mechanical properties of a colloidal gel can give way to kinetics of settling very different from usual suspensions which can no longer be described using a simple PNK model. In particular, we study the influence of the very voluminous sediment generally formed in such systems. We thus propose a complete description of the kinetics of a settling colloidal gel according to its volume fraction and to the cell inclination angle. In the experimental section, the predicted settling regimes are compared to experimental results obtained with calcium carbonate suspensions. The agreement between theoretical expressions and experiments is good which shows that our results are relevant to most experimental studies of tenuous colloidal gels.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 2 (2000), S. 47-57 
    ISSN: 1292-895X
    Keywords: PACS 61.30.Jf Defects in liquid crystals – 61.72.Lk Linear defects: dislocation disclinations – 61.72.Mm Grain and twin boundaries
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Focal Conic Domains (FCDs) in smectic phases often assemble according to a particular rule, experimentally discovered by G. Friedel, the law of corresponding cones (l.c.c.). This paper reports various results relating to this type of association. First we show that a l.c.c. contact between 2 focal conic domains has a vanishing energy, yielding metastable local equilibrium. Then we use some projective properties of conic sections to extend the celebrated Apollonian tiling, which describes a tilt grain boundary (TiGB) of vanishing disorientation made of toric focal conic domains, to any TiGB. Finally we present a realistic model of the energy of the TiGB, which we compare to the energy of a TiGB split into dislocations, and to the energy of a curvature wall. This model explains why FCD tilings show macroscopic zones not filled with FCDs.
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