Search results for " mechanics"
showing 10 items of 5066 documents
Towards a local approach to fatigue, for the calculation of structures, applied to continuous fibre reinforced composite materials and structures
2018
The original concept of mechanical fatigue was linked to the failure of structures and was treated at first within the framework of Fracture Mechanics. Models developed to explain this phenomenon must therefore be able to be applied to structures: changing the structure means changes to the model and its identification. It is therefore judicious to develop models capable of treating both the damage processes and also able to be used within a local framework: to this end a method based on Damage Mechanics seems appropriate. This approach has long been employed and requires only the identification of damage processes at the level of the RVE (Representative Volume Element) to be used for any s…
Functional Fibronectin Adsorption on Aptamer-Doped Chitosan Modulates Cell Morphology by Integrin-Mediated Pathway.
2019
A decisive step in cell-biomaterial interaction is represented by the adsorption of proteins at the interface, whose fine control may be useful to trigger proper cell response. To this purpose, we can selectively control protein adsorption on biomaterials by means of aptamers. Aptamers selected to recognize fibronectin dramatically enhance chitosan ability to promote cell proliferation and adhesion, but the underlying biological mechanism remains unknown. We supposed that aptamers contributed to ameliorate the adsorption of fibronectin in an advantageous geometrical conformation for cells, thus regulating their morphology by the proper activation of the integrin-mediated pathway. We investi…
A quantum mechanics-molecular mechanics study of dissociative electron transfer : The methylchloride radical anion in aqueous solution
2002
The dissociative electron transfer reaction CH3Cl+e−→CH3•+Cl− in aqueous solution is studied by using a QM/MM method. In this work the quantum subsystem (a methylchloride molecule plus an electron) is described using density functional theory while the solvent (300 water molecules) is described using the TIP3P classical potential. By means of molecular dynamics simulations and the thermodynamic integration technique we obtained the potential of mean force (PMF) for the carbon–chlorine bond dissociation of the neutral and radical anion species. Combining these two free energy curves we found a quadratic dependence of the activation free energy on the reaction free energy in agreement with Ma…
ON THE EFFECTS OF A CRACK PROPAGATING TOWARD THE INTERFACE OF A BIMATERIAL SYSTEM
2006
This paper deals with the influence of matrix cracks on the failure mode of bimaterial systems and composite materials. In order to investigate such an influence, the stress field near a crack embedded into the more yielding material and propagating perpendicularly to the interface, has been analyzed by using systematic numerical simulations. Such analysis has shown that the crack propagation give rises to transversal stresses that can damage the reinforcing materials when this has low modulus, as glass fibers, or low transversal strength, such as carbon fibers. Moreover, the longitudinal stress concentration can damage the reinforcing material only if this has high stiffness, as in the cas…
Comparison between probe stagnation point heat flux measurements and correlation formulas in SCIROCCO plasma wind tunnel tests
2012
A large part of the SCIROCCO Arc Heater Performance Map has been investigated. The heat flux measurements at the stagnation point of t he facility Calibratio Probe have been used to find an experimental fit. Such a formula ha s been compared with the predictions of the De Filippis-Serpico equation and the well known Fay-Riddell formula. Finally the experimental fit has been also compared with the Sa gner-Verant formula obtained at the ONERA F4 hypersonic plasma wind tunnel.
On the global dissipative and multipeakon dissipative behavior of the two-component Camassa-Holm system
2014
Published version of an article in the journal: Abstract and Applied Analysis. Also available from the publisher at: http://dx.doi.org/10.1155/2014/348695 Open Access The global dissipative and multipeakon dissipative behavior of the two-component Camassa-Holm shallow water system after wave breaking was studied in this paper. The underlying approach is based on a skillfully defined characteristic and a set of newly introduced variables which transform the original system into a Lagrangian semilinear system. It is the transformation, together with the associated properties, that allows for the continuity of the solution beyond collision time to be established, leading to a uniquely global d…
The AVL-mode: a safe closed loop algorithm for ventilation during total intravenous anesthesia.
1994
The Adaptive Lung Ventilation Controller (ALV-Controller) represents a new approach to closed loop control of ventilation. It is based on a pressure controlled ventilation mode. Adaptive lung ventilation signifies automatic breath by breath adaptation of breathing patterns to the lung mechanics of an individual patient. The specific goals are to minimize work of breathing, to maintain a preset alveolar ventilation and to prevent the occurrence of intrinsic PEEP. We ventilated 5 patients undergoing major abdominal procedures using ALV. ALV was tolerated well in all patients. Alveolar ventilation was preset between 5500 and 6500 ml/min. Serial dead space (Vds) and respiratory time constant (r…
Critical energy flux and mass in solvable theories of 2D dilaton gravity
1998
In this paper we address the issue of determining the semiclassical threshold for black hole formation in the context of a one-parameter family of theories which continuously interpolates between the RST and BPP models. We find that the results depend significantly on the initial static configuration of the spacetime geometry before the influx of matter is turned on. In some cases there is a critical energy density, given by the Hawking rate of evaporation, as well as a critical mass $m_{cr}$ (eventually vanishing). In others there is neither $m_{cr}$ nor a critical flux.
Integrable models and degenerate horizons in two-dimensional gravity
1999
We analyse an integrable model of two-dimensional gravity which can be reduced to a pair of Liouville fields in conformal gauge. Its general solution represents a pair of ``mirror'' black holes with the same temperature. The ground state is a degenerate constant dilaton configuration similar to the Nariai solution of the Schwarzschild-de Sitter case. The existence of $\phi=const.$ solutions and their relation with the solution given by the 2D Birkhoff's theorem is then investigated in a more general context. We also point out some interesting features of the semiclassical theory of our model and the similarity with the behaviour of AdS$_2$ black holes.
Diffeomorphisms, Noether charges, and the canonical formalism in two-dimensional dilaton gravity
1995
We carry out a parallel study of the covariant phase space and the conservation laws of local symmetries in two-dimensional dilaton gravity. Our analysis is based on the fact that the Lagrangian can be brought to a form that vanishes on-shell giving rise to a well-defined covariant potential for the symplectic current. We explicitly compute the symplectic structure and its potential and show that the requirement to be finite and independent of the Cauchy surface restricts the asymptotic symmetries.