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Seddik H.,Hokkaido University | Greve R.,Hokkaido University | Zwinger T.,Center for Science Ltd. | Placidi L.,International Telematic University Uninettuno
Cryosphere | Year: 2011

A three-dimensional, thermo-mechanically coupled ice flow model with induced anisotropy has been applied to a ∼200 × 200 km domain around the Dome Fuji drill site, Antarctica. The model ("Elmer/Ice") is based on the open-source multi-physics package Elmer (http://www.csc.fi/elmer/) and solves the full Stokes equations. Flow-induced anisotropy in ice is accounted for by an implementation of the Continuum-mechanical, Anisotropic Flow model, based on an anisotropic Flow Enhancement factor ("CAFFE model"). Steady-state simulations for present-day climate conditions are conducted. The main findings are: (i) the flow regime at Dome Fuji is a complex superposition of vertical compression, horizontal extension and bed-parallel shear; (ii) for an assumed geothermal heat flux of 60 mW m-2 the basal temperature at Dome Fuji reaches the pressure melting point and the basal melting rate is ∼0.35 mm a -1; (iii) in agreement with observational data, the fabric shows a strong single maximum at Dome Fuji, and the age of the ice is decreased compared to an isotropic scenario; (iv) as a consequence of spatially variable basal melting conditions, the basal age tends to be smaller where the ice is thicker and larger where the ice is thinner. The latter result is of great relevance for the consideration of a future drill site in the area. © Author(s) 2011.

Placidi L.,International Telematic University Uninettuno
Continuum Mechanics and Thermodynamics | Year: 2016

A one-dimensional displacement second-gradient damage continuum theory has been already presented within the framework of a variational approach. Damage is associated with strain concentration. Therefore, not only non-local effects of displacement second-gradient modelling should be considered in a comprehensive model, but also any plastic effects. The aim of this paper is therefore to extend such a model to plasticity. The action is intended to depend not only with respect to first and second gradient of displacement field and to a scalar damage field, but also to further two internal variables, i.e. the accumulated plastic tension and the accumulated plastic compression. A constitutive prescription on the stiffness is given in terms of the scalar damage parameter in a usual way, i.e. as in many other works, it is prescribed to decrease as far as the damage increases. On the other hand, the microstructural material length (i.e. the square of the constitutive function in front of the squared displacement second-gradient term in the action functional) is prescribed to increase as far as the damage increases, being this last assumption connected to the interpretation that a damage state induces a microstructure in the continuum and that such a microstructure is more important as far as the damage increases. Initial damage threshold and yield stresses are naturally introduced in the action in front of linear terms, respectively, of damage and plastic internal variables. The hardening matrix is also introduced in a natural way as the coefficient matrix in front of the quadratic terms of the two plastic internal variables. At a given value of damage and plastic parameters, the behaviour is referred to second-gradient linear elastic material. However, the damage and plastic evolutions make the model not only nonlinear, but also inelastic. The second principle of thermodynamics is considered by assuming that the scalar damage and plastic parameters do not decrease their values in the process of deformation, and this implies a dissipation for the elastic strain energy. A novel result of this investigation, where displacement second-gradient and plastic effects are combined, is that the distributed and concentrated external double forces do not make work on the displacement gradient but only to its elastic part and this means that the displacement gradient cannot be prescribed, at the border, independently of the plastic internal variables. © 2014, Springer-Verlag Berlin Heidelberg.

Cerniglia L.,International Telematic University Uninettuno | Cimino S.,University of Rome La Sapienza | Ballarotto G.,University of Rome La Sapienza
Infant Mental Health Journal | Year: 2014

The article aims to study mother-child and father-child interactions with 24-month-old children during feeding, considering the possible influence of time spent by the parent with the child, the infantile temperament, and the parental psychological profile. The families were recruited from 12 preschools in Italy (N = 77 families). Through an observation of the feeding [Scala di Valutazione dell'Interazione Alimentare (SVIA - Feeding Scale; I. Chatoor et al., 1997; L. Lucarelli et al., 2002)], self-reporting [Symptom Checklist-90-Revised (SCL-90-R; L.R. Derogatis, 1994), and report-form questionnaires [Italian Questionnaires on Temperament (QUIT; G. Axia, 2002)], and information provided by the parents about the amount of time spent with their children, results showed that the overall quality of father-child interactions during feeding is lower than that of mother-child interactions. Fathers showed higher psychological symptoms than did mothers. No associations were found between the fathers' psychopathological risk and the quality of interactions with their children during feeding. Mothers' psychopathological risks predicted less contingent exchanges interactions with their children during feeding. Children's temperaments significantly influence mother-child interactions, but no association exists between maternal involvement and the quality of interactions with their children. Paternal involvement predicts a better quality of father-infant interactions when associated with a child's higher scores on Social Orientation. The quality of parents' interactions with their children during feeding are impacted by different issues originating from the parent's psychological profile, the degree of involvement, and from the child's temperament. © 2014 Michigan Association for Infant Mental Health.

Dell'Isola F.,University of Rome La Sapienza | Andreaus U.,University of Rome La Sapienza | Placidi L.,International Telematic University Uninettuno
Mathematics and Mechanics of Solids | Year: 2015

Gabrio Piola's scientific papers have been underestimated in mathematical physics literature. Indeed, a careful reading of them proves that they are original, deep and far-reaching. Actually, even if his contribution to the mechanical sciences is not completely ignored, one can undoubtedly say that the greatest part of his novel contributions to mechanics, although having provided a great impetus to and substantial influence on the work of many preeminent mechanicians, is in fact generally ignored. It has to be remarked that authors Capecchi and Ruta dedicated many efforts to the aim of unveiling the true value of Gabrio Piola as a scientist; however, some deep parts of his scientific results remain not yet sufficiently illustrated. Our aim is to prove that non-local and higher-gradient continuum mechanics were conceived already in Piola's works and to try to explain the reasons for the unfortunate circumstance which caused the erasure of the memory of this aspect of Piola's contribution. Some relevant differential relationships obtained in Piola (Memoria intorno alle equazioni fondamentali del movimento di corpi qualsivogliono considerati secondo la naturale loro forma e costituzione, 1846) are carefully discussed, as they are still too often ignored in the continuum mechanics literature and can be considered the starting point of Levi-Civita's theory of connection for Riemannian manifolds. © 2015 SAGE Publications.

Andreaus U.,University of Rome La Sapienza | Placidi L.,International Telematic University Uninettuno | Rega G.,University of Rome La Sapienza
Journal of Applied Physics | Year: 2013

Microcantilever dynamics in tapping mode atomic force microscopy (AFM) is addressed via a multimode approximation, which allows to consider external excitation at primary or secondary resonance and to highlight the effect of higher order eigenmodes. Upon presenting the AFM model and its multimode discretization, the dynamic response is investigated via numerical simulation of single- and three-mode models by considering different bifurcation parameters. Typical features of tapping mode AFM response as nonlinear hysteresis, bistability, higher harmonics contribution, impact velocity, and contact force are addressed. The analysis is conducted by evaluating damping of higher modes according to the Rayleigh criterion, which basically accounts for structural damping representative of the behavior of AFMs in air. Nominal damping situations more typical of AFMs in liquids are also investigated, by considering sets of modal Q-factors with different patterns and ranges of values. Variable attractive-repulsive effects are highlighted, along with the possible presence of a coexisting multi-periodic orbit when the system is excited at second resonance. © 2013 AIP Publishing LLC.

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