Search results for " Scienza"

Per una genealogia della biopoetica. Da Aristotele a Todorov

2021

Negli ultimi anni la teoria letteraria in Italia ha cominciato ad affrontare la questione del significato biologico della narrazione e della letteratura.1 Il presupposto di questo interesse sta nel riconoscimento che la narrazione può essere a pieno titolo considerata un “comportamento” tipico dell’Homo Sapiens, non foss’altro perché è un fenomeno che riguarda tutta la specie (a tutte le latitudini e a tutte le altezze cronologiche) e può essere studiata nel quadro delle attitudini cognitive che hanno permesso agli umani di costruire la loro specifica nicchia ecologica. In recent years, literary theory in Italy has begun to address the question of the biological meaning of narration and lit…

PREPARATION AND CHARACTERIZATION OF BIOPOLYMERIC POROUS STRUCTURES FOR ADVANCED APPLICATIONS

Porous biopolymers received an increasing academic and industrial interest finding application in several fields such as tissue engineering, bioprocess intensification and waste removal. Tissue engineering combines the knowledge of materials science and bioengineering in order to develop structures able to substitute and restore the normal function of injured or diseased tissues. In this context, polymeric 3D or 2D scaffolds are widely investigated as temporary cell guidance during the tissue restore. Porous biomaterials can offer a versatile and cost effective way for immobilization of filamentous microorganisms in submerged fermentation processes for the production of biologically active …

Wave propagation in 1D elastic solids in presence of long-range central interactions

2011

Abstract In this paper wave propagation in non-local elastic solids is examined in the framework of the mechanically based non-local elasticity theory established by the author in previous papers. It is shown that such a model coincides with the well-known Kroner–Eringen integral model of non-local elasticity in unbounded domains. The appeal of the proposed model is that the mechanical boundary conditions may easily be imposed because the applied pressure at the boundaries of the solid must be equilibrated by the Cauchy stress. In fact, the long-range forces between different volume elements are modelled, in the body domain, as central body forces applied to the interacting elements. It is …

Variational Aspects of the Physically-Based Approach to 3D Non-Local Continuum Mechanics

2010

This paper deals with the generalization to three-dimensional elasticity of the physically-based approach to non-local mechanics, recently proposed by the authors in one-dimensional case. The proposed model assumes that the equilibrium of a volume element is attained by contact forces between adjacent elements and by long-range central forces exerted by non-adjacent elements. Specifically, the long-range forces are modeled as central body forces depending on the relative displacements between the centroids of the volume elements, measured along the line connecting the centroids. Furthermore, the long-range forces are assumed to be proportional to a proper, material-dependent, distance-decay…

Physically-Based Approach to the Mechanics of Strong Non-Local Linear Elasticity Theory

2009

In this paper the physically-based approach to non-local elasticity theory is introduced. It is formulated by reverting the continuum to an ensemble of interacting volume elements. Interactions between adjacent elements are classical contact forces while long-range interactions between non-adjacent elements are modelled as distance-decaying central body forces. The latter are proportional to the relative displacements rather than to the strain field as in the Eringen model and subsequent developments. At the limit the displacement field is found to be governed by an integro-differential equation, solved by a simple discretization procedure suggested by the underlying mechanical model itself…

A generalized model of elastic foundation based on long-range interactions: Integral and fractional model

2009

The common models of elastic foundations are provided by supposing that they are composed by elastic columns with some interactions between them, such as contact forces that yield a differential equation involving gradients of the displacement field. In this paper, a new model of elastic foundation is proposed introducing into the constitutive equation of the foundation body forces depending on the relative vertical displacements and on a distance-decaying function ruling the amount of interactions. Different choices of the distance-decaying function correspond to different kind of interactions and foundation behavior. The use of an exponential distance-decaying function yields an integro-d…

Long-range interactions in 1D heterogeneous solids with uncertainty

2013

Abstract In this paper, the authors aim to analyze the response of a one-dimensional non-local elastic solid with uncertain Young's modulus. The non-local effects are represented as long-range central body forces between non-adjacent volume elements. Following a non-probabilistic approach, the fluctuating elastic modulus of the material is modeled as an interval field. The analysis is conducted resorting to a novel formulation that confines the overestimation effect involved in interval models. Approximate closed-form expressions are derived for the bounds of the interval displacement field.

The mechanically-based approach to 3D non-local linear elasticity theory: Long-range central interactions

2010

Abstract This paper presents the generalization to a three-dimensional (3D) case of a mechanically-based approach to non-local elasticity theory, recently proposed by the authors in a one-dimensional (1D) case. The proposed model assumes that the equilibrium of a volume element is attained by contact forces between adjacent elements and by long-range forces exerted by non-adjacent elements. Specifically, the long-range forces are modelled as central body forces depending on the relative displacement between the centroids of the volume elements, measured along the line connecting the centroids. Further, the long-range forces are assumed to be proportional to a proper, material-dependent, dis…

Mechanically-based approach to non-local elasticity: Variational principles

2010

Abstract The mechanically-based approach to non-local elastic continuum, will be captured through variational calculus, based on the assumptions that non-adjacent elements of the solid may exchange central body forces, monotonically decreasing with their interdistance, depending on the relative displacement, and on the volume products. Such a mechanical model is investigated introducing primarily the dual state variables by means of the virtual work principle. The constitutive relations between dual variables are introduced defining a proper, convex, potential energy. It is proved that the solution of the elastic problem corresponds to a global minimum of the potential energy functional. Mo…

One-dimensional heterogeneous solids with uncertain elastic modulus in presence of long-range interactions: Interval versus stochastic analysis

2013

The analysis of one-dimensional non-local elastic solids with uncertain Young's modulus is addressed. Non-local effects are represented as long-range central body forces between non-adjacent volume elements. For comparison purpose, the fluctuating elastic modulus of the material is modeled following both a probabilistic and a non-probabilistic approach. To this aim, a novel definition of the interval field concept, able to limit the overestimation affecting ordinary interval analysis, is introduced. Approximate closed-form expressions are derived for the bounds of the interval displacement field as well as for the mean-value and variance of the stochastic response.