Farms as a resilience factors to land degradation in peri-urban areas

The purpose of this study was the analysis of the effects induced by urban pressures on the socio-economic and territorial characteristics of the rural peri-urban areas in order to identify planning and intervention strategies aimed at enhancing the quality of agriculture and landscape. A survey was conducted in the surroundings of Parma on farms located in the vicinity of urban areas. The structural, productive and social characteristics of the family-farm units were analyzed. The survey updated an identical survey, carried out in 1986, in which it was examined a sample of 208 farms. The units surveyed were evaluated in two aspects: the “vitality”, which takes into account the structural characteristics (size, production, labour force, etc.), and the “stability”, in which a crucial role is played by the age of the conductor and the presence of a successor. It was found that only 28% of the original farm sample is still alive, one third has disappeared, 30% was absorbed by existing farms, 8% has been abandoned. The factors most favourable to the survival resulted those referred to the vitality, especially the physical and economic size of the farm, the presence of cattle, the percentage of land in property, the presence of young labour. Among the factors that predispose to the abandonment, the urbanization processes were found to be determinants, in terms of expansion of both the built-up area and of that planned as urbanisable. The research has highlighted the importance of the vitality of the farms together with a context that has maintained its original rural features. These combined aspects can better define what we call the resiliency of the landfarms system i.e. the capability of positively reacting to the variable modifications of the internal and external conditions

A port-Hamiltonian formulation of flexible structures. Modelling and structure-preserving finite element discretization

Despite the large literature on port-Hamiltonian (pH) formalism, elasticity problems in higher geometrical dimensions have almost never been considered. This work establishes the connection between port-Hamiltonian distributed systems and elasticity problems. The originality resides in three major contributions. First, the novel pH formulation of plate models and coupled thermoelastic phenomena is presented. The use of tensor calculus is mandatory for continuum mechanical models and the inclusion of tensor variables is necessary to obtain an equivalent and intrinsic, i.e. coordinate free, pH description. Second, a finite element based discretization technique, capable of preserving the structure of the infinite-dimensional problem at a discrete level, is developed and validated. The discretization of elasticity problems requires the use of non-standard finite elements. Nevertheless, the numerical implementation is performed thanks to well-established open-source libraries, providing external users with an easy to use tool for simulating flexible systems in pH form. Third, flexible multibody systems are recast in pH form by making use of a floating frame description valid under small deformations assumptions. This reformulation include all kinds of linear elastic models and exploits the intrinsic modularity of pH systems

Intrinsic nonlinear elasticity: An exterior calculus formulation

In this paper we formulate the theory of nonlinear elasticity in a geometrically intrinsic manner using exterior calculus and bundle-valued differential forms. We represent kinematics variables, such as velocity and rate-of-strain, as intensive vector-valued forms while kinetics variables, such as stress and momentum, as extensive covector-valued pseudo-forms. We treat the spatial, material and convective representations of the motion and show how to geometrically convert from one representation to the other. Furthermore, we show the equivalence of our exterior calculus formulation to standard formulations in the literature based on tensor calculus. In addition, we highlight two types of structures underlying the theory. First, the principle bundle structure relating the space of embeddings to the space of Riemannian metrics on the body, and how the latter represents an intrinsic space of deformations. Second, the de Rham complex structure relating the spaces of bundle-valued forms to each other