Search results for " Mathematica"
showing 10 items of 689 documents
Periodic unmixing of a binary metallic vapor
2005
We report on a type of surface structuring after short pulse laser ablation of a binary alloy. We observe the emergence of a concentric ring structure with changing elemental composition. The composition changes are interpreted by condensation of the ambient ablation vapor due to stress wave excitations in the ablation spot.
Portfolios with fuzzy returns: Selection strategies based on semi-infinite programming
2008
AbstractThis paper provides new models for portfolio selection in which the returns on securities are considered fuzzy numbers rather than random variables. The investor's problem is to find the portfolio that minimizes the risk of achieving a return that is not less than the return of a riskless asset. The corresponding optimal portfolio is derived using semi-infinite programming in a soft framework. The return on each asset and their membership functions are described using historical data. The investment risk is approximated by mean intervals which evaluate the downside risk for a given fuzzy portfolio. This approach is illustrated with a numerical example.
Cross-Efficiency in Fuzzy Data Envelopment Analysis (FDEA): Some Proposals
2013
Different techniques have been proposed in the literature to rank decision making units (DMUs) in the context of Fuzzy Data Envelopment Analysis. In our opinion, those that result from using a ranking method to order the fuzzy efficiencies obtained are susceptible to a serious criticism: they are not based on objective criteria. Cross-efficiency evaluation was introduced as an extension of DEA aimed at ranking the DMUs. This methodology has found a significant number of applications and has been extensively investigated. In this chapter, we discuss some difficulties that arise with the definition of fuzzy cross-efficiencies and we propose a fuzzy cross-efficiency evaluation based on the FDE…
Modelling agricultural risk in a large scale positive mathematical programming model
2020
International audience; Mathematical programming has been extensively used to account for risk in farmers' decision making. The recent development of the positive mathematical programming (PMP) has renewed the need to incorporate risk in a more robust and flexible way. Most of the existing PMP-risk models have been tested at farm-type level and for a very limited sample of farms. This paper presents and tests a novel methodology for modelling risk at individual farm level in a large scale model, called individual farm model for common agricultural policy analysis (IFM-CAP). Results show a clear trade-off between including and excluding the risk specification. Albeit both alternatives provid…
Main Fuel Cells mathematical models: Comparison and analysis in terms of free parameters
2010
This paper resumes the main mathematical models of Fuel Cells (PEM models). In particular, a comparison study of the various models introduced in the technical literature is presented and the dependency of the various model parameters is analyzed in different operating conditions. As the manifold of the model parameter is very wide and their determination is difficult, it is mandatory to introduce approximations and simplifications on which each model is based. The novelty of this work is the organization of the existing models in three categories with regard to the number of free parameters and to the dependency of such parameters on the different running conditions and the usage of a refe…
Non-dominated “trade-off” solutions in television scheduling optimization
2014
The main approaches for the television scheduling design are commonly based on the ratings or revenues maximization objective, and thus, only a single optimal solution can be obtained, corresponding to the best result for the considered objective. Therefore, these approaches lead up to the alternative solutions loss which, even if less effective from the ratings or revenues maximization viewpoint, may be more suitable for the decision maker because of better compromise in relation to factors influencing the decision process. Specifically, such a compromise could be achieved through a suitable “trade-off” between these factors, with reference to the decision context in which the decision mak…
Applying fuzzy Particle Swarm Optimization to Multi-unit Double Auctions
2010
Abstract In the context of Quadratic Programming Problems, we use a fuzzy Particle Swarm Optimization (PSO) algorithm to analyze a Multi-unit Double Auction (MDA) market. We give also a Linear Programming (LP) based upper bound to help the decision maker in dealing with constraints in the mathematical model. In the computational study, we evaluate our algorithm and show that it is a feasible approach for processing bids and calculating assignments.
Introducing migratory flows in life table construction
2012
The purpose of life tables is to describe the mortality behav iour of particular groups. The construction of general life tables is based on death statis tics and census figures of resident populations under the hypothesis of closed demographic sys tem. Among other assumptions, this hypothesis implicitly assumes that entries (immigrants) a nd exits (emigrants) of the population are usually not significant (being almost of the same magnitu de for each age compensating each other). This paper theoretically extends the classical sol ution to open demographic systems and studies the impact of this hypothesis in constructing a life table. In particular, using the data of residential variations m…
Corrigendum to ``A smooth foliation of the 5-sphere by complex surfaces"
2011
International audience
Quasiregular ellipticity of open and generalized manifolds
2014
We study the existence of geometrically controlled branched covering maps from \(\mathbb R^3\) to open \(3\)-manifolds or to decomposition spaces \(\mathbb {S}^3/G\), and from \(\mathbb {S}^3/G\) to \(\mathbb {S}^3\).