Search results for "Elasticity"
showing 10 items of 736 documents
A hierarchy of simplified constitutive models within isotropic strain gradient elasticity
2017
Abstract Simplified isotropic models of strain gradient elasticity are presented, based on the mutual relationship between the inherent (dual) gradient directions (i.e. the gradient direction of any strain gradient source and the lever arm direction of the promoted double stress). A class of gradient-symmetric materials featured by gradient directions obeying a reciprocity relation and by 4 independent h.o. (higher order) coefficients is envisioned, along with the sub-classes of hemi-collinear materials (3 h.o. coefficients, gradient directions in part coincident), collinear materials (2 h.o. coefficients, equal gradient directions) and micro-affine materials (1 h.o. coefficient, behavioral…
Ferroelasticity and glass-like behavior in alkali halide-alkali cyanide mixed crystals
1991
Abstract Single crystal neutron diffraction studies in (KBr)1-x(KCN)x are summarized. Mixed crystals with CN− concentrations x > 0.6 exhibit ferroelastic phase transitions from a high-temperature plastic phase into a low-temperature elastically ordered phase in which the CN− orientations show long range orientational order and the center of mass lattice exhibits shear distortions. For concentrations x ≤ 0.6 orientational disorder is frozen-in and transitions into an orientational glass state occur. Close to the critical concentration xc ∼ 0.6 the diffraction profiles at the transition temperatures are dominated by diffuse-scattering contributions. These results are compared to model calcula…
Structural and elastic properties of defect chalcopyrite HgGa2S4 under high pressure
2014
In this work, we focus on the study of the structural and elastic properties of mercury digallium sulfide (HgGa2S4) at high pressures. This compound belongs to the family of AB(2)X(4) ordered-vacancy compounds and exhibits a tetragonal defect chalcopyrite structure. X-ray diffraction measurements at room temperature have been performed under compression up to 15.1 GPa in a diamond anvil cell. Our measurements have been complemented and compared with ab initio total energy calculations. The axial compressibility and the equation of state of the low-pressure phase of HgGa2S4 have been experimentally and theoretically determined and compared to other related ordered-vacancy compounds. The pres…
Ferroelastic Fingerprints in Methylammonium Lead Iodide Perovskite
2016
Methylammonium lead iodide (MAPbI3) perovskite shows an outstanding performance in photovoltaic devices. However, certain material properties, especially the possible ferroic behavior, remain unclear. We observed distinct nanoscale periodic domains in the piezoresponse of MAPbI3(Cl) grains. The structure and the orientation of these striped domains indicate ferroelasticity as their origin. By correlating vertical and lateral piezoresponse force microscopy experiments performed at different sample orientations with X-ray diffraction, the preferred domain orientation is suggested to be the a1–a2-phase. The observation of these ferroelastic fingerprints appears to strongly depend on the film t…
A dynamic panel study on digitalization and firm's agility: What drives agility in advanced economies 2009–2018
2021
Abstract Firm agility today is not a factor of competitiveness or success but a survival instrument on the market. Disruptive innovations and technological advancement, together with digitalization, change the role of firm agility. We show that the link between the national/industry level of digitalization and firm agility is statistically robust and essential. We study the link on data from 2009 to 2018 in fifteen EU advanced economies using dynamic panel data modeling. The digitalization impact level differs across firms by ownership type (family to non-family firms). Agility in family firms is strongly influenced by the national/industry level of digitization and investments in intangibl…
Vibrations of weakly coupled nanoparticles
2009
The vibrations of a coupled pair of isotropic silver spheres are investigated and compared with the vibrations of the single isolated spheres. Situations of both strong coupling and also weak coupling are investigated using continuum elasticity and perturbation theory. The numerical calculation of the eigenmodes of such dimers is augmented with a symmetry analysis. This checks the convergence and applicability of the numerical method and shows how the eigenmodes of the dimer are constructed from those of the isolated spheres. The frequencies of the lowest frequency vibrations of such dimers are shown to be very sensitive to the strength of the coupling between the spheres. Some of these mod…
A regular variational boundary model for free vibrations of magneto-electro-elastic structures
2011
In this paper a regular variational boundary element formulation for dynamic analysis of two-dimensional magneto-electro-elastic domains is presented. The method is based on a hybrid variational principle expressed in terms of generalized magneto-electro-elastic variables. The domain variables are approximated by using a superposition of weighted regular fundamental solutions of the static magneto-electro-elastic problem, whereas the boundary variables are expressed in terms of nodal values. The variational principle coupled with the proposed discretization scheme leads to the calculation of frequency-independent and symmetric generalized stiffness and mass matrices. The generalized stiffne…
MAPPINGS OF FINITE DISTORTION: $L^n \log^{\alpha} L$ -INTEGRABILITY
2003
Recently, systematic studies of mappings of finite distortion have emerged as a key area in geometric function theory. The connection with deformations of elastic bodies and regularity of energy minimizers in the theory of nonlinear elasticity is perhaps a primary motivation for such studies, but there are many other applications as well, particularly in holomorphic dynamics and also in the study of first order degenerate elliptic systems, for instance the Beltrami systems we consider here.
Theory of heterogeneous viscoelasticity
2015
We review a new theory of viscoelasticity of a glass-forming viscous liquid near and below the glass transition. In our model we assume that each point in the material has a specific viscosity, which varies randomly in space according to a fluctuating activation free energy. We include a Maxwellian elastic term and assume that the corresponding shear modulus fluctuates as well with the same distribution as that of the activation barriers. The model is solved in coherent-potential approximation (CPA), for which a derivation is given. The theory predicts an Arrhenius-type temperature dependence of the viscosity in the vanishing-frequency limit, independent of the distribution of the activatio…
Is Participation in Tourism Market an Opportunity for Everyone? Some Evidence from Italy
2014
Exploring the main determinants of tourism participation at national and international level, the paper investigates if there are differences in tourism consumption behavior among Italian families which reflect disparities in their standard of living. To achieve this a Heckman model has been used on a huge sample of Italian households over the period 1997-2007. Results show that participation in the tourism market is strongly affected by the personal characteristics of individuals and that tourism consumption is an income sensitive good. The analysis reveals that tourism is generally a luxury good reflecting the disparities in the standard of living among Italian families. We have found tha…