170,153 research outputs found
Application of Particle Swarm Optimization to Formative E-Assessment in Project Management
No full textThe current paper describes the application of Particle Swarm Optimization algorithm to the formative e-assessment problem in project management. The proposed approach resolves the issue of personalization, by taking into account, when selecting the item tests in an e-assessment, the following elements: the ability level of the user, the targeted difficulty of the test and the learning objectives, represented by project management concepts which have to be checked. The e-assessment tool in which the Particle Swarm Optimization algorithm is integrated is also presented. Experimental results and comparison with other algorithms used in item tests selection prove the suitability of the proposed approach to the formative e-assessment domain. The study is presented in the framework of other evolutionary and genetic algorithms applied in e-education.Particle Swarm Optimization, Genetic Algorithms, Evolutionary Algorithms, Formative E-assessment, E-education
Smart City Analytics: state of the art and future perspectives
No full textIn accordance with a 'people centred' vision, this paper critically examines current approaches to smart cities benchmarking. In particular, by means of correlation analysis and Principal Component Analysis (PCA) we put in evidence present limitations of city rankings and, as well, the emergence of different perspectives for data interpretations. To follow, a possible redesign of the 'Smart Cities Analytics' grounded on the traces left by individuals, is suggested. In particular, as an example, we focus on the potentiality offered by automatic text analysis to extract people perceptions and expectations that, in turns, demonstrate the need to integrate bottom-up and top-down approaches to city benchmarking. Finally a novel definition of smart city based on the territorial state of flow is proposed and, as a consequence, a novel path toward smart city benchmarking suggested
Electrical behavior of nematic cells oriented by polypyrrole surface treatment
No full textWe have studied the electrical response of nematic liquid crystal cells with uniform planar alignment imposed by ClO(4)(-) doped polypyrrole layers. From the measured electrical current on a resistance in series with the nematic sample when applying a triangular potential with different periods and amplitudes, the diffusion of the ions from the polypyrrole layer into the liquid crystal was evidenced. The sample is described as an insulating liquid containing a distribution of ions depending on the characteristics of the applied external field and also of the polymer layers. A simple model concerning the diffusion of the ions from the aligning doped polypyrrole film inside the liquid crystal is proposed. The agreement between experimental data and numerical results is good
The 3D Smith Chart and its practical applications
No full textMueller, A.; Dascalu, DC.; Soto Pacheco, P.; Boria Esbert, VE. (2012). The 3D Smith Chart and its practical applications. Microwave journal. 55(7):64-72. https://riunet.upv.es/handle/10251/52766S647255
A simple model of ac hopping surface conductivity in ionic liquids
No full textThe boundary conditions proposed to discuss the charge exchange taking place in an ionic liquid in contact with non-blocking electrodes are reconsidered in a dynamic situation. Assuming that the variation of the bulk ionic current density depends linearly on the surface value of the ionic current density, the frequency dependence of the phenomenological parameter is determined. The analysis has been performed in the framework where the relaxation times are smaller than a maximum relaxation time τM, and that the response function is independent on the value of the relaxation time. Using simple physical considerations, an expression for the surface conductivity describing the ionic charge exchange at the electrode is obtained. According to our calculations, its frequency dependence is similar to that predicted for the electric conductivity in disordered materials when the mechanism is of the hopping type. From measurements of impedance spectroscopy, by the best fit of the experimental data, the temperature dependence of the hopping time, of the dc surface conductivity, and of the diffusion coefficient are derived. They are in good agreement with the theoretical predictions obtained with the random distribution of surface energy barrier. Keywords: Ionic liquids, Non-blocking electrodes, Electrical impedance spectroscopy, AC hopping surface conductivit
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Experimental evidence for Ohmic behavior of a 5CB planar cell limited by ITO-electrodes in the DC limit
No full textThe influence of the electrode properties on the electric response of nematic liquid crystal cell limited by ITO surfaces is investigated. From electrochemical impedance spectroscopy measurements (EIS) of the real and imaginary parts of the electric impedance of the cell it is evident that in the DC limit the cell behaves as a pure resistance, since its reactance tends to zero linearly with the frequency of the applied voltage. The spectrum of the real part of the impedance shows the presence of two plateaux, one related to the bulk properties of the cell, and the other to the electrode properties. The experimental data can be interpreted in terms of Poisson- Nernst-Planckmodel, assuming that the presence of the non-blocking electrodes is described by a boundary condition according to which the conduction current across the electrode due to the charge exchange between ions and electrons is due to the surface electric field, as in Ohmic electrodes, and to the variation of the bulk density of ions just in front to the electrodes, as in the Chang-Jaffe mode
The Year of Living Dangerously
No full textWe consider the issue N. 46 particularly significant because it comes at the end of 2020, a year that marked the recent history of humanity. On one side, the pandemic reminded us how fragile mankind is and that it can succumb to a small and invisible enemy; on the other side, the Covid-19 challenged and stimulated the potential of our intelligence and creativity that, when driven by collaboration and solidarity, can be very high. The effects of the pandemic inevitably put under stress all learning ecosystems of the world that had to switch suddenly to the on-line modality and remained confined to this virtual dimension for a long time. It was a leap into the shadow, if not into darkness, the consequences of which are still to be fully understood; at present they are still, and will remain for a long time, under investigation
- …
