1,720,977 research outputs found
“L’economia politica della democrazia nell’Italia settentrionale: 1796-1799”, Economies et Sociétés, série "Oeconomia" PE.
No full textEnsemble Aggregation Approaches for Functional Optimization
No full textIn this work we investigate the use of ensemble methods, consisting in the aggregation of several approximating models, in the context of functional optimization. In fact, while ensemble techniques are routinely employed in the machine learning literature for classification and regression, there is little research on their application to general optimization problems. Here we consider two strategies to aggregate different solutions to a functional optimization problem, based on optimized weighted averaging and aggregation over the minimum, the latter also in approximate version. A theoretical analysis of approximate functional optimization in the context of ensemble aggregation is provided. Then, simulation results are reported to showcase the advantages of ensembles for functional optimization, in terms of better accuracy and improved robustness with respect to single solutions
QuantTree: Histograms for change detection in multivariate data streams
No full textWe address the problem of detecting distribution changes in multivariate data streams by means of histograms. Histograms are very general and flexible models, which have been relatively ignored in the change-detection literature as they often require a number of bins that grows unfeasibly with the data dimension. We present QuantTree, a recursive binary splitting scheme that adaptively defines the histogram bins to ease the detection of any distribution change. Our design scheme implies that i) we can easily control the overall number of bins and ii) the bin probabilities do not depend on the distribution of stationary data. This latter is a very relevant aspect in change detection, since thresholds of tests statistics based on these histograms (e.g., the Pearson statistic or the total variation) can be numerically computed from univariate and synthetically generated data, yet guaranteeing a controlled false positive rate. Our experiments show that the proposed histograms are very effective in detecting changes in high dimensional data streams, and that the resulting thresholds can effectively control the false positive rate, even when the number of training samples is relatively small
Influence of rare earths addition on the corrosion behaviour of Zn-5%Al (Galfan) alloy in neutral aerated sodium sulphate solution
No full textThe effect of rare earth metal (Ce, Er, Y) additions on the corrosion behaviour of Zn-5Al Galfan alloy has been investigated. The corrosion resistance of Zn-5Al-1Ce, Zn-5Al-1Er and Zn-5Al-1Y alloys has been assessed by various electrochemical tests, such as corrosion potential measurements, polarization curves and electrochemical impedance spectroscopy. They have been performed in a 0.1 M Na2 SO4 solution, at approximately neutral pH, without stirring and in contact with the air. For comparison, the electrochemical tests have also been carried out on the Zn-5Al alloy. Moreover, the surface morphology and nature of the corrosion products have been investigated. The results indicated that rare earths' addition improves the corrosion behaviour of Galfan, the effect being more pronounced for the Er- and Y-containing alloys. The mechanism by which the corrosion resistance of Zn-5Al alloy is enhanced in presence of the rare earths is discusse
Investigation o the elctrocatalytic behaiour of Fe-MM (MM = Mischmetal) crystalline alloys for the hydrogen evolution reaction in alkaline medium
No full textFe-MM (MM = mischmetal) crystalline alloys have been characterized by means of microstructural and electrochemical techniques in view of their possible application as electrocatalytic materials for the hydrogen evolution reaction (HER). The microstructure of the alloys investigated (Fe95 MM5 , Fe85 MM15 , Fe80 MM20 , Fe70 MM30 ) has been characterized by phase analysis techniques (SEM-EPMA, XRD). The electrocatalytic efficiency has been evaluated on the basis of electrochemical data obtained from cathodic polarization curves and ac impedance measurements carried out in 1 M NaOH solution at 298 K. The microstructural features play a fundamental role in determining the electrocatalytic activity of the investigated alloys. The overall experimental data indicate that interesting electrocatalytic performances are obtained with the Fe80 MM20 electrode, which exhibits the highest activity towards the HE
Effect of Nb alloying additions on the characteristics of anodic oxide films on zirconium and their stability in NaOH solution
No full textThe characteristics of oxide films on Zr and Zr- Nb alloys (with Nb content of 2.5, 5, and 10 at.%) galvanostatically formed (at a current density of 100 μA cm−2) in 0.5 M H2SO4 solution were investigated by means of electrochemical impedance spectroscopy. Electrochemical impedance spectroscopy spectra were interpreted in terms of an "equivalent circuit" with the circuit elements representing the electrochemical properties of a single layer oxide. The resistance of the oxide films was found to increase with increased Nb content in the alloy while the capacitance showed an opposite trend. The stability of the anodic oxide films grown in the sulfuric acid solution on Zr and Zr-Nb alloys was investigated by simultaneously measuring the electrode capacitance and resistance at a working frequency of 1 kHz as a function of exposure time to naturally aerated 3 M NaOH solution. Analyses of the electrode capacitance and resistance values indicated a decrease in chemical dissolution rate of the oxide films with the increase of Nb content in the alloy
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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