1,721,004 research outputs found
Response to Comment on “On the Origin of Frictional Energy Dissipation”, by B.N.J. Persson
Full text linkWe are grateful to Dr. B.N.J. Persson for his prompt attention to our work (Hu et al. in Tribol Lett, https://doi.org/10.1007/s11249-019-1247-7, 2020). In his Comment, he remarks (i) that near-critical damping of motion in/on solids, one of our main results, is well known for atoms and molecules at surfaces and (ii) that this result may be invalid for real practical cases (Persson in Tribol Lett, this issue). We fully agree with both statements. However, some discussion is justified.</p
Adhesion between an elastic body and a randomly rough hard surface
No full textI have developed a theory of adhesion between an elastic solid and a hard randomly rough substrate. The theory takes into account that partial contact may occur between the solids on all length scales. I present numerical results for the case where the substrate surface is self-affine fractal. When the fractal dimension is close to 2, complete contact typically occurs in the macro-asperity contact areas, while when the fractal dimension is larger than 2.5, the area of (apparent) contact decreases continuously when the magnification is increased. An important result is that even when the surface roughness is so high that no adhesion can be detected in a pull-off experiment, the area of real contact (when adhesion is included) may still be several times larger than when the adhesion is neglected. Since it is the area of real contact which determines the sliding friction force, the adhesion interaction may strongly affect the friction force even when no adhesion can be detected in a pull-off experiment
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
LATERAL INTERACTIONS IN SMALL PARTICLE SYSTEMS
No full textNous discutons, dans cet exposé, une théorie générale des propriétés optiques des systèmes de petites particules. Nous considérons d'abord les propriétés vibrationnelles de mélanges isotopiques de molécules en interaction dipolaire adsorbées selon une structure ordonnée sur une surface métallique. Les propriétés de ce système sont calculées en utilisant l'approximation du potentiel cohérent (APC). Ensuite, nous analysons les propriétés optiques de systèmes de petites particules métalliques à deux et trois dimensions. Un modèle de gaz de réseau est utilisé pour simuler une distribution quasi aléatoire de particules et l'APC est appliquée à l'obtention d'une solution au problème du désordre. Pour tous les systèmes étudiés le désordre introduit, dans le spectre d'absorption, une structure caractéristique qui est en bon accord avec l'expérience.In this review I will discuss a general theory for the optical properties of small particle systems. I first consider the vibrational properties of isotopic mixtures of dipole interacting molecules adsorbed in an ordered structure on a metal surface. The properties of this system are calculated using the coherent potential approximation (CPA). Next I discuss the optical properties of two and three dimensional systems of small metallic particles. A lattice gas model is used to simulate nearly randomly distributed particles and the CPA is applied to obtain a solution of the disorder problem. For all studied systems the disorder introduces characteristic structure in the absorption spectra which compares favourably with experiments
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