Search results for "cost"

Les étudiants anticipent-ils correctement la valeur de leur diplôme sur le marché du travail ?

2013

Documents de travail de l'IREDU, n°2013-1; Ce travail analyse la manière dont les étudiants de première année d'université anticipent leurs salaires futurs, puis compare ces salaires à ceux qu'ils peuvent réellement observer sur le marché du travail. Nos résultats montrent globalement une surestimation des salaires anticipés d'environ 9 pour cent en début de carrière, ce qui est cohérent avec des travaux réalisés dans d'autres pays. En revanche, les salaires anticipés après dix ans de carrières sont supérieurs de 28 pour cent aux salaires observés des diplômés à ancienneté comparable. Les résultats soulignent également l'importance de l'environnement familial lors du choix des études supéri…

Comparing conventional and organic citrus grower efficiency in Spain

2014

This paper compares the organic and conventional citriculture systems in Spain from the perspective of their technical efficiency. The primary objective of the research is to compare the relative efficiency of these two systems in relation to a metafrontier that envelops both technologies. In addition, the article analyses how efficient each growing system is at using its own technology, that is, when farms’ efficiency is benchmarked in relation to the best practices in their group. Contrary to conventional practice, farms’ performance is analyzed in terms of specific growing tasks: soil and plant cover management, pruning, fertilization and phytosanitary treatments. The results obtained hi…

Mother and offspring fitness in an insect with maternal care: phenotypic trade-offs between egg number, egg mass and egg care

2014

Background Oviparous females have three main options to increase their reproductive success: investing into egg number, egg mass and/or egg care. Although allocating resources to either of these three components is known to shape offspring number and size, potential trade-offs among them may have key impacts on maternal and offspring fitness. Here, we tested the occurrence of phenotypic trade-offs between egg number, egg mass and maternal expenditure on egg care in the European earwig, Forficula auricularia, an insect with pre- and post-hatching forms of maternal care. In particular, we used a series of laboratory observations and experiments to investigate whether these three components no…

An extended shakedown theory for elastic-plastic-damage material models

1996

Internal variable elastic-plastic-damage, or elastic-damage, material models endowed with free energy are considered. Referring to a structure of such a material subjected to loads varying inside a given domain, the classical notion of (elastic) shakedown is widened to signify that the structure eventually responds to the loads in an elastic manner after certain (finite) amounts of plastic strain and/or damage have been produced. For structures fulfilling an ad-hoc D-stability requisite, an extended shakedown theorem is presented as a generalization of the classical Melan theorem to nonlinear elasticity and damage - besides nonlinear hardening. For common materials exhibiting linear elastic…

MULTICRITERIA OPTIMAL DESIGN OF CONTINUOUS CIRCULAR PLATES

2010

The paper is devoted to a quite general version of the multicriteria optimal (minimum volume) design of axisymmetric circular plates. The constitutive material is considered as elastic perfectly plastic without any ductility limit and the actions are assumed as quasi-statically variable within a given load domain. In the design problem formulation different resistance criteria are considered, in order to investigate all the possible structural limit responses, and for each one a suitably chosen safety factor is chosen. The optimal design problem is formulated as the search for the minimum structure volume according with a statical approach. The features of the optimal structures will be stu…

Reliable measures of plastic deformations for elastic plastic structures in shakedown conditions

2020

A new formulation for evaluating reliable measures of the plastic deformations occurring in the transient phase of a structure in shakedown conditions is proposed. The structure is thought as constituted by elastic perfectly plastic material and subjected to a combination of fixed and cyclic loads. The proposed formulation consists in the search for the optimal plastic strain field that minimize a suitable objective function defining a strain energy measure related to the plastic strains at the shakedown limit. The typical self-stress field can be obtained as the elastic structural response to an assigned plastic strain field respecting appropriate ductility limits for the material. Without…

Influence of protecting devices on the optimal design of elastic plastic structures

2008

The paper concerns the minimum volume design of structures constituted by elastic perfectly plastic material. The relevant optimal design problem is formulated on the grounds of a statical approach and two different resistance limits are considered: in particular, it is required that the optimal structure satisfies the elastic shakedown limit and the instantaneous collapse limit, imposing for each different condition a suitably chosen safety factor. For sake of generality, the structure is thought as discretized into compatible finite elements and subjected to loads quasi-statically acting as well as to dynamic (seismic) loads. The effects of the dynamic actions are studied on the grounds o…

Discussion: “Chaotic Motion of an Elastic-Plastic Beam” (Poddar, B., Moon, F. C., and Mukherjee, S., 1988, ASME J. Appl. Mech., 55, pp. 185–189)

1988

Discussion on caotic motion of a pinned beam subjected to pulse loading

Elastoplastic analysis by the multidomain Symmetric Boundary Element Method

2009

On the FE·Meshless computational homogenization for the analysis of two-dimensional heterogeneous periodic materials

2017

Over the last few years, substantial progresses have been made in the two-scales com- putational homogenization. This method is essentially based on the assessment of the macroscopic constitutive behavior of heterogeneous materials through the boundary value problem (BVP) of a statistically representative volume element, named as unit cell (UC). In this framework, the first-order method has now matured to a standard tool and several extensions have been addressed in the literature [1, 2]. In the present study, a first-order homogenization scheme based on a discontinuous- continuous approach is presented. At the mesoscopic level the formation and propagation of fracture is modeled employing …