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  • 1
    Electronic Resource
    Electronic Resource
    Contribution to the theory of diffusion-reaction controlled Liesegang patterns (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 1499-1504 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A Turing-type reaction-diffusion model is explored which may be applicable to Liesegang bands, rings, and spirals evolving by precipitation in the environs of an equilibrium solubility product relation. Because of their incompletely specified initial and (or) boundary conditions the solutions exhibit a bivariate free boundary degeneracy. We find that one degree of freedom may be removed by the specification of a global rate constant and the other by the specification of a principle of optimal wave number selection within linear stability theory. Existence conditions for banding in one dimension are established and these agree with particular observations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456092
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  • 2
    Electronic Resource
    Electronic Resource
    Nanoindentation investigation of the Young's modulus of porous silicon (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 3772-3776 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Young's modulus of porous silicon samples, with porosity ranging from 36% to 90%, is measured by the nanoindentation technique. The analysis of the nanoindentation data, including the specific problem linked with porous materials, is presented. The Young's modulus values Ep thus obtained appear to be drastically dependent on the porosity and on the doping level (p or p+ type). The dependence of Ep versus the relative density (for a series of p+ type samples) is quadratic, in good agreement with the model of Gibson and Ashby developed for cellular materials. This also shows that highly porous silicon layers exhibit very low Young's modulus (for a porosity of 90% it is about two orders of magnitude smaller than that of the nonporous material). © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363305
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  • 3
    Electronic Resource
    Electronic Resource
    Study of the cracking of highly porous p+ type silicon during drying (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 7586-7591 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The origin of the cracking of highly porous silicon layers during drying is investigated. Optical and scanning electron microscopy observation allow us to observe the cracking occurrence. In situ x-ray diffraction experiments, under controlled vapor pressure of pentane, reveal that large capillary stresses occur at a vapor pressure P* during the controlled drying. These stresses lead to the cracking of the highly porous layer, which occurs for samples thicker than a critical thickness hc. Taking into account the mechanical properties of the material, a model based on energy balance is presented. This model predicts a layer thickness hc of cracking occurrence, showing that hc varies as (1−p)3/γLV2 (where γLV is the surface tension of the drying liquid and p is the porosity). This model is in good agreement with experimental data obtained with two liquids, water, and pentane, which have very different surface tension and also for two different porosities. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362415
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  • 4
    Electronic Resource
    Electronic Resource
    Self-organizing processes The sound of many hands clapping (2000)
    [s.l.] : Macmillan Magazines Ltd.
    Nature 403 (2000), S. 849-850 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] An audience expresses appreciation for a good performance by the strength and nature of its applause. The thunder of applause at the start often turns quite suddenly into synchronized clapping, and this synchronization can disappear and reappear several times during the applause. The ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/35002660
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  • 5
    Electronic Resource
    Electronic Resource
    On a model of frictional sliding (1996)
    Springer
    Pure and applied geophysics 147 (1996), S. 745-762 
    Details
    ISSN: 1420-9136
    Keywords: Frictional sliding ; crustal fault ; stick-slip ; stability analysis ; models of earthquakes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A model of frictional sliding with anN-shaped curve for the sliding velocity dependence of the coefficient of friction is considered. This type of friction law is shown to be related to dynamic i.e., velocity dependent ‘ageing’ of asperity junctions. Mechanisms of ‘ageing’ for ductile (Bowden-Tabor) and brittle (Byerlee) materials, though different in nature, lead to qualitatively similarN-shaped velocity dependencies of the coefficient of friction. Estimates for the velocities limiting the range of negative velocity sensitivity of the coefficient of friction are obtained for the ductile case and—albeit with a lesser degree of reliability—for the brittle one. It is shown by linear stability analysis that discontinuous sliding (stick-slip) is associated with thedescending portion of theN-shaped curve. An instability criterion is obtained. An expression for the period of the attendant relaxation oscillations of the sliding velocity is given in terms of the calculated velocity dependence of the coefficient of friction. It is suggested that the micromechanically motivated friction law proposed should be used in models of earthquakes due to discontinuous frictional sliding on a crustal fault.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01089700
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  • 6
    Electronic Resource
    Electronic Resource
    Fatigue of Al-Li alloys: mechanical properties, microstructure (TEM and SEM) and strain localization (1990)
    Springer
    Journal of materials science 25 (1990), S. 3053-3060 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The fatigue behaviour of two binary AI-Li alloys (A, solid solution; B, containing δ′ precipitates) is studied by macroscopic fatigue tests, and microscopic (SEM and STEM) observations. Two types of strain localization are found, appearing as two types of slip band in SEM, and as two types of substructure in TEM. These characteristics are ascribed to strain localization processes governed by strain amplitude for the former and strain rate for the latter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00587649
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  • 7
    Electronic Resource
    Electronic Resource
    On the threshold pinning force in type II superconducting films (1989)
    Springer
    Journal of low temperature physics 74 (1989), S. 293-318 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The maximum pinning force of a two-dimensional vortex lattice in a random potential is calculated. A connection is established between this threshold pinning force and the potential energy discontinuities due to elastic and plastic instabilities of the vortex lattice. Inspired by recent computer simulations, we assume that the fluctuations in the commensurability between the random potential and the vortex potential breaks the vortex system up into a set of flowing channels in between trapped regions. Two instability mechanisms and their contribution to the threshold force are discussed within this channel-flow picture. We find that three different regimes exist depending on, w, the width of the channels;w=∞,a 0〈w〈∞, and finallyw=a 0 , wherea 0 is the vortex lattice spacing. Weak pinning superconductors can pass through all three regimes as the reduced magnetic field is varied from 0 to 1, whereas strong pinning compounds can remain in the saturated region (w=a 0 ) for all values of the field. We compare the expression for the threshold force with experimental results for both strong and weak pinning samples. A satisfactory qualitative agreement is obtained between theory and experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00683377
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  • 8
    Electronic Resource
    Electronic Resource
    High-temperature plasticity of two-phase alloys: Constitutive laws and microstructure evolution (1995)
    Springer
    Czechoslovak journal of physics 45 (1995), S. 883-891 
    Details
    ISSN: 1572-9486
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Modelling high-temperature deformation of two-phase alloys present some specific difficulties compared to the similar problem in pure metals. Some of the open questions associated with these specificities are reviewed. Special attention is given to the relative importance of internal stress and structural hardening, to the derivation and parameter identification of constitutive laws in industrial alloys, and to microstructure evolution during plasticity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01692006
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  • 9
    Electronic Resource
    Electronic Resource
    Characterization of the damage in nanocomposite materials by a.c. electrical properties: experiment and simulation (1999)
    Springer
    Journal of materials science 34 (1999), S. 1753-1759 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Evolution of a.c. electrical properties under large strain of random nanocomposite materials made of a soft thermoplastic insulating matrix and hard conductive fillers is investigated. The transport properties are directly linked with the macroscopic mechanical strain on the composites during uniaxial tensile test or to the time under relaxation, meaning that the method is suitable for monitoring microstructural evolution of such composites. The real part of the conductivity indicated the breaking of the percolating network, while the imaginary part gave information on the possible “spatial correlation” of the damage events. Two different filler shapes were used, i.e. spherical and stick-like (aspect ratio about 15), leading to quantitatively different results. The microstructural evolution was simulated with the help of a resistance–capacitance (RC) model for the electrical properties and with finite element analysis for the mechanical properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004546806226
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  • 10
    Electronic Resource
    Electronic Resource
    Reduced Mobility of Triple Nodes and Lines on Grain Growth in Two and Three Dimensions (1999)
    Springer
    Interface science 7 (1999), S. 285-295 
    Details
    ISSN: 1573-2746
    Keywords: computer simulation ; growth ; energy dissipation ; grain boundaries ; triple nodes (Interfaces) ; triple line (Interfaces)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Vertex dynamics models in two and three dimensions are applied to study grain growth including a limited mobility of triple points (two dimensions) and triple lines (three dimensions). A recent experiment on a triple node is used to validate the proposed model. The reduced triple node/line mobility in the case of a polycrystalline sample is shown to influence both, the grain growth kinetics and the grain size distribution function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008773411083
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