Subadditive Discount Functions with a Transition Period

In this paper, the dosage of the times in the repeated and fractionable actions is studied. The interventions in time are abstract in nature and deal also with the psychological aspect of the individual behavior, in a wider perspective of utility, or the management of procedures in output systems. Furthermore, decomposability of discount functions is explored, and time period splitting plans are considered. Such procedures are analyzed, for instance, in the treatment of drug addiction, and various applications in behavioral sciences have been found. We wonder whether it would be convenient an infinite subdivision, that is, a finest fragmentation of time period (for a medical treatment, or a financial process, or a man‐machine interrelation); or, on the contrary, a possible efficient subdivision must be bounded. Specifically, we deal with the problem of finding the expression of a discount function able to distinguish between favorableness and unfavorableness of the refinements of splitting levels for general processes.     

Mechanical Properties of Double-Layer and Graded Composite Coatings of YSZ Obtained by Atmospheric Plasma Spraying

Double-layer and graded composite coatings of yttria-stabilized zirconia were sprayed on metallic substrates by atmospheric plasma spray. The coating architecture was built up by combining two different feedstocks: one micro- and one nanostructured. Microstructural features and mechanical properties (hardness and elastic modulus) of the coatings were determined by FE-SEM microscopy and nanoindentation technique, respectively. Additional adherence and scratch tests were carried out in order to assess the failure mechanisms occurring between the layers comprising the composites. Microstructural inspection of the coatings confirms the two-zone microstructure. This bimodal microstructure which is exclusive of the layer obtained from the nanostructured feedstock negatively affects the mechanical properties of the whole composite. Nanoindentation tests suitably reproduce the evolution of mechanical properties through coatings thickness on the basis of the position and/or amount of nanostructured feedstock used in the depositing layer. Adhesion and scratch tests show the negative effect on the coating adhesion of layer obtained from the nanostructured feedstock when this layer is deposited on the bond coat. Thus, the poor integrity of this layer results in lower normal stresses required to delaminate the coating in the adhesion test as well as minor critical load registered by using the scratch test.     

Study and experimental verification of control tuning strategies in a variable speed wind energy conversion system

This paper analyzes and compares different control tuning strategies for a variable speed wind energy conversion system (WECS) based on a permanent-magnet synchronous generator (PMSG). The aerodynamics of the wind turbine (WT) and a PMSG have been modeled. The control strategy used in this research is composed of three regulators, which may be based on either linear or nonlinear controllers. In this analysis, proportional-integral (PI) linear controllers have been used. Two different tuning strategies are analyzed and compared. The main goal is to enhance the overall performance by achieving a low sensitivity to disturbances and minimal overshoot under variable operating conditions. Finally, the results have been verified by an experimental WECS laboratory prototype.     

Statistical characterization of P2P-TV services and users

P2P-TV systems will certainly contribute to innovate the broadcast TV concept by allowing ubiquitous access to a practically unlimited number of channels, representing an important step forward in the direction of the Anything/Anyone/Anywhere/Anytime communication paradigm of future Internet applications. Since its deployment, P2P-TV has already attracted millions of users and it is expected to grow exponentially in the near future, both in terms of the number and diversity of their clients. Analyzing the behavior of P2P-TV systems and users and characterizing the generated traffic are fundamental steps to understand and evaluate the potential impacts of these applications on the underlying transport network. In this paper, a set of intensive measurements was conducted in a residential Internet access environment in order to obtain a good insight over the mechanisms that govern data transfer on some of the most important P2P-TV applications (TVants, SOPCast and TVU Player) and understand the most important advances they have suffered in the latest years. Among other relevant findings, the analysis showed that peer location does not seem to be exploited by any of the studied applications and P2P-TV is already a worldwide phenomenon: using the three selected applications during 12 days of experiments, peers from 177 different countries all over the world were contacted, including countries where the interest for English-spoken channels was not so likely.     

Estimating willingness to pay for desalinated seawater: the case of Djerba Island,Tunisia

Water scarcity can be a growth-limiting factor. Non-conventional water resources, such as desalinated water, represent an alternative means of guaranteeing access to water while reducing water stress. In this study, a contingent valuation survey carried out in Djerba Island, Tunisia, allows the joint modelling of two decisions: societal support for the construction of a desalination plant and households’ willingness to pay for desalinated water. To the best of the authors’ knowledge, no study to date has addressed this relationship. We find that although a clear majority of households are in favour of using desalinated water, far fewer are willing to pay for it. The article concludes that it is worth studying willingness to pay for desalinated water in developing countries in order to avoid investing in projects where it is doubtful that costs will be recouped.