Search results for "Elasticity"
showing 10 items of 736 documents
A fractional order theory of poroelasticity
2019
Abstract We introduce a time memory formalism in the flux-pressure constitutive relation, ruling the fluid diffusion phenomenon occurring in several classes of porous media. The resulting flux-pressure law is adopted into the Biot’s formulation of the poroelasticity problem. The time memory formalism, useful to capture non-Darcy behavior, is modeled by the Caputo’s fractional derivative. We show that the time-evolution of both the degree of settlement and the pressure field is strongly influenced by the order of Caputo’s fractional derivative. Also a numerical experiment aiming at simulating the confined compression test poroelasticity problem of a sand sample is performed. In such a case, …
Fractional visco-elastic Euler–Bernoulli beam
2013
Abstract Aim of this paper is the response evaluation of fractional visco-elastic Euler–Bernoulli beam under quasi-static and dynamic loads. Starting from the local fractional visco-elastic relationship between axial stress and axial strain, it is shown that bending moment, curvature, shear, and the gradient of curvature involve fractional operators. Solution of particular example problems are studied in detail providing a correct position of mechanical boundary conditions. Moreover, it is shown that, for homogeneous beam both correspondence principles also hold in the case of Euler–Bernoulli beam with fractional constitutive law. Virtual work principle is also derived and applied to some c…
Demographic change, tourism expenditure and life cycle behavior
2015
Abstract The paper explores how demographic changes in human populations may impact on tourism decision-making of households over their life cycle. By means of hurdle models, the study focuses respectively on the decision to travel domestically or abroad and investigates if statistically significant differences exist as to the impact of age and cohort on the decision to travel and tourism expenditure. Using a vast dataset on Italian Household Expenditures over the period 1997–2007 the empirical results show that demographic aspects do have a strong effect on the tourism behaviour of families and that cohort and age effects act differently on the decision of households to make a trip and on …
Intertemporal Substitution in the Spanish Economy: Evidence from Regional Data*
2018
This paper studies the intertemporal substitution in consumption and leisure for the Spanish economy by estimating the first‐order conditions of an individual optimization model with regional and aggregate data. While first‐order conditions determining intertemporal substitution in consumption show a good econometric fit, and the value we obtain for the intertemporal elasticity of substitution is similar to previously available results, the econometric fit of the intertemporal condition in leisure indicates that the behaviour of the Spanish labour supply over the cycle is more complex than can be explained by the canonical intertemporal choice model.
Is participation in the tourism market an opportunity for everyone? Some evidence from Italy
2016
This paper investigates whether there are differences in tourism consumption behaviour among families by analysing the main determinants of tourism participation at national and international levels. In particular, it explores whether tourism is becoming part of the lifestyle of Italians or whether it is still a luxury good only for the privileged. A Heckman model was used on micro-data on Italian family expenditure over the period 1997–2007, and an income elasticity analysis for different personal and household characteristics was carried out. The results show that participation in the tourism market is strongly affected by the personal characteristics of individuals and that tourism cons…
A Hierarchical Model for Analysing Consumption Patterns in Italy Before and During the Great Recession
2016
The paper aims to explore how the Great Recession of the twenty-first century has impacted on the consumption behaviour of Italian households. Following a hierarchical approach, the study investigates differences in consumption behaviour at both household and regional levels. Using micro data on Italian Household Expenditure for the years 2002, 2006, 2010 and 2012, multilevel and two-step regression models have been estimated. The analysis has been performed for four different consumption categories: food, housing, work-related and leisure. The analysis reveals that the economic crisis led to increasing income elasticity for each category of consumption, especially for food, the most essent…
Nonsmooth Mechanics. Convex and Nonconvex Problems
1999
Nonlinear, multivalued and possibly nonmonotone relations arise in several areas of mechanics. A multivalued or complete relation is a relation with complete vertical branches. Boundary laws of this kind connect boundary (or interface) quantities. A contact relation or a locking mechanism between boundary displacements and boundary tractions in elasticity is a representative example. Material constitutive relations with complete branches connect stress and strain tensors, or, in simplified theories, equivalent stress and strain quantities. A locking material or a perfectly plastic one is represented by such a relation. The question of nonmonotonicity is more complicated. One aspect concerns…
A Theoretical Model to Evaluate the Compressive Behaviour of RС Jacketed Columns
2016
Reinforced concrete (RC) jacketing is becoming increasingly common among the different retrofit techniques for poor RC members, due to its economical and practical advantages. Experimental investigations in the literature have shown that the actual axial capacity of RC jacketed members can be substantially lower than that analytically evaluated by adapting the most common theoretical models for confined concrete. This fact can be explained by taking into account the presence of tensile stresses developing in the concrete, due to a mutual interaction between the inner core and the external jacket. This phenomenon is relevant especially in members where the concrete properties of the jacket a…
Reliability Estimation of Optimal Viscoelastic Composite Shells in Critical-Time Calculations
2003
The problem of reliability estimation for optimal viscoelastic composite shells in critical-time calculations is considered. The weight minimization of a viscoelastic composite shell, with constraints on deflections at the critical time, leads to a system deforming unstably, whose deflections grow in time with an increasing rate. A method for estimating the reliability of such shells in calculating the critical time is discussed. This time is regarded as a random variable depending on many, roughly equivalent, factors. An analysis of the reliability is carried out for different values of coefficients of variation, occurring in practice.
DSC, Dilatometric, Dielectric, and1H NMR Studies of Phase Transitions and Molecular Motions in [N(C2H5)4]3M2Cl9 (M = Sb, Bi) Crystals
1995
Results in the dependence of stoichiometry of obtained tetraethylammonium (TEA) chloroantiomonate and chlorobismuthate salts on the molar ratio of reactants used in the synthesis are presented. Seven tetraethylammonium salts are obtained: (TEA) 6 M 8 Cl 30 , TEAMCI 4 , (TEA) 3 M 2 Cl 9 (M = Sb, Bi) and (TEA) 2 SbCl 5 . Preliminary X-ray diffraction studies on (TEA) 3 M 2 Cl 9 (M = Sb, Bi) show that they are isomorphous, crystallizing at room temperature in monoclinic symmetry. The dilatometric, dielectric, and DSC studies show that (TEA) 3 Bi 2 Cl 9 undergoes two phase transitions at T c2 = 144 K and at T c1 = 322 K while (TEA) 3 Sb 2 Cl 9 undergoes three transitions at T c3 = 185, T c2 = 2…