Visualisation graphique de la propagation des ondes assistée par ordinateur

On studies of propagation and scattering phenomena by numerical methods, one of the difficulties encountered is the physical interpretation of the great number of numerical values obtained. A clear and easy interpretation of such results is presented here, by using graphic techniques.     

Second-order sliding-mode control of DC drives

One of the most recent topics in variable-structure systems theory is represented by the second-order sliding-mode control (2-SMC) methodology. This approach guarantees the same robustness and dynamic performance of traditional first-order SMC algorithms, and, at the same time, attenuates the chattering phenomenon, which is the main drawback in the actual implementation of this technique. In the present paper, a recently-proposed 2-SMC algorithm is used to synthesize a robust dc-drive control system which does not require current feedback and demands only rough information about the actual motor parameters. Stability and performance are analyzed, and an experimental comparison with a proportional-integral-based control scheme is reported.     

Distributed parametric and nonparametric regression with on-line performance bounds computation

In this paper we focus on collaborative multi-agent systems, where agents are distributed over a region of interest and collaborate to achieve a common estimation goal. In particular, we introduce two consensus-based distributed linear estimators. The first one is designed for a Bayesian scenario, where an unknown common finite-dimensional parameter vector has to be reconstructed, while the second one regards the nonparametric reconstruction of an unknown function sampled at different locations by the sensors. Both of the algorithms are characterized in terms of the trade-off between estimation performance, communication, computation and memory complexity. In the finite-dimensional setting, we derive mild sufficient conditions which ensure that a distributed estimator performs better than the local optimal ones in terms of estimation error variance. In the nonparametric setting, we introduce an on-line algorithm that allows the agents to simultaneously compute the function estimate with small computational, communication and data storage efforts, as well as to quantify its distance from the centralized estimate given by a Regularization Network, one of the most powerful regularized kernel methods. These results are obtained by deriving bounds on the estimation error that provide insights on how the uncertainty inherent in a sensor network, such as imperfect knowledge on the number of agents and the measurement models used by the sensors, can degrade the performance of the estimation process. Numerical experiments are included to support the theoretical findings.     

Antioxidant capacity,ascorbic acid,total phenols and carotenoids changes during harvest and after storage of Hayward kiwifruit

The influences of harvest time and storage on the quality indices and nutritional content of kiwifruit were evaluated. Antioxidant capacity, ascorbic acid, total phenol content, carotenoids, soluble solids content and flesh firmness were determined in kiwifruit gathered at two different time (T1: 17-11-2005 and T2: 24-11-2005) and stored at 0 °C, for 2 or 6 months (S1 and S2, respectively). At the end of the cool storage, fruits were maintained for a week at 25 °C (S1 + 7d and S2 + 7d).     

Effects of foliar and fruit addition of sodium selenate on selenium accumulation and fruit quality

BACKGROUND: We investigated the effects of the foliar and fruit application of sodium selenate on selenium (Se) accumulation, fruit growth and ripening in peach and pear. Trials were conducted in two growing seasons. In 2008 selenate was applied at a rate of 0.1 and 1.0 mg Se L^?1 to the leaves of peach. In 2009 selenate was applied at a rate of 1 mg Se L^?1 via foliar (LT) or fruit (FT) application to peach and pear. RESULTS: The foliar addition of selenate to peach resulted in an increase in Se concentration both in leaves and fruit. The higher Se content in fruit resulted in an increase in flesh firmness and a decrease in soluble solid content. LT significantly increased the Se content in the leaves and fruit of peach and pear, and leaves showed the highest Se concentrations. FT increased the fruit Se concentration in both crops, and it was more effective than LT in increasing Se content. After storage, flesh firmness decreased in all treatments, but it was significantly higher in FT compared to LT and control samples. CONCLUSION: Foliar and fruit selenium spraying appeared effective in increasing the Se content of fruit in peach and pear. The enhanced Se concentration affected the shelf life of fruit, delaying the reduction in flesh firmness and fruit ripening, thus positively affecting fruit storage. Copyright © 2011 Society of Chemical Industry     

Preliminary characterisation of peach cultivars for their antioxidant capacity

Eleven peach cultivars (white‐ and yellow‐flesh peaches, nectarines and canning clingstone peaches) were assayed for their antioxidant capacity and their content of some important organic compounds as well as vitamin C, carotenoids and phenols. Antioxidant capacity, determined by FRAP assay, varied between genotypes. Those with the highest value of Ferric Reducing Antioxidant Power (FRAP) were Federica and Springcrest. Antioxidant capacity was correlated to the amount of organic components with significant differences among the cultivars. In some case, antioxidant capacity was related to phenol content, as in yellow–flesh peaches. These results suggest the importance of genotype for determining antioxidant capacity, which, in turn, is related to the organic constituents, such as phenols, vitamin C and carotenoids.     

Machine Vision for Size Distribution Determination of Spherically Shaped Particles in Dense-Granular Beds,Oriented to Pelletizing Process Automation

A machine vision has been devised for determination of the size distribution of spherically shaped pellets in granular beds under static and dynamic conditions. This machine vision involved establishing the optimal distance between the illumination source and the top layer of the granular bed, as well as the development of the data image acquisition software and control systems, I/O interface hardware, and electromechanical system. The size distribution of pellets given by the whole system gives an error lower than 5% for pellets. The size distribution histogram or the Sauter diameter of the pellets given by the vision system is used as the input signal for controlling an electromechanical scanning device, which can be reliably used for automation tasks. The system software was developed for open access on a commercially widely used platform. As the machine vision is robust, it can be used in industrial environments and it has the potential to contribute in improving and optimizing pelletizing industrial processes. This machine vision is reliable, flexible, user friendly, inexpensive, and easy to implement.     

Computer-algebra systems and electromagnetic problems

This paper presents some computer-algebra systems, and explains how these systems are likely to be relevant in addressing electromagnetic problems. After a historical survey, we discuss the various systems and their features. Some examples are given, with an important bibliography. A listing of Web sites (of interest to the antennas and propagation community) is also given. Finally, we outline how a given problem can be formalized and analyzed using symbolic-algebra systems, and show an example calculation for a conformal-microstrip antenna