Trolls Identification within an Uncertain Framework

The web plays an important role in people's social lives since the emergence of Web 2.0. It facilitates the interaction between users, gives them the possibility to freely interact, share and collaborate through social networks, online communities forums, blogs, wikis and other online collaborative media. However, an other side of the web is negatively taken such as posting inflammatory messages. Thus, when dealing with the online communities forums, the managers seek to always enhance the performance of such platforms. In fact, to keep the serenity and prohibit the disturbance of the normal atmosphere, managers always try to novice users against these malicious persons by posting such message (DO NOT FEED TROLLS). But, this kind of warning is not enough to reduce this phenomenon. In this context we propose a new approach for detecting malicious people also called 'Trolls' in order to allow community managers to take their ability to post online. To be more realistic, our proposal is defined within an uncertain framework. Based on the assumption consisting on the trolls' integration in the successful discussion threads, we try to detect the presence of such malicious users. Indeed, this method is based on a conflict measure of the belief function theory applied between the different messages of the thread. In order to show the feasibility and the result of our approach, we test it in different simulated data.Comment: International Conference on Tools with Artificial Intelligence - ICTAI , Nov 2014, Limassol, Cypru

Magnetodynamic vector hysteresis models for steel laminations of rotating electrical machines

This thesis focuses on the modeling and prediction of iron losses in rotating electrical machines. The aim is to develop core loss models that are reasonably accurate and efficient for the numerical electromagnetic field analysis. The iron loss components, including hysteresis, classical eddy-current, and excess losses, are determined by modeling the dynamic hysteresis loops, whereby the incorporation of the core losses into the field solution is feasible and thus the influence of the core losses on the performance of the machine is investigated. The thesis presents a magnetodynamic vector hysteresis model that produces not only an accurate, overall prediction of the iron losses, but also explicitly models the magnetization behavior and the loop shapes. The model is found to be efficient, stable, and adequate for providing accurate predictions of the magnetization curves, and hence iron losses, under alternating and rotating flux excitations. It is demonstrated that the model satisfies the rotational loss property and reproduces the shapes of the experimental loops. In addition, a more simplified, efficient, and robust version of the magnetodynamic vector hysteresis model is introduced. The thesis also aims to analyze the convergence of the fixed-point method, examine the barriers behind the slow convergence, and show how to overcome them. The analysis has proved useful and provided sound techniques for speeding up the convergence of the fixed-point method. The magnetodynamic lamination models have been integrated into a two-dimensional finite-element analysis of rotating electrical machines. The core losses of two induction motors have been analyzed and the impact of core losses on the motor characteristics has been investigated. The simulations conducted reveal that the models are relatively efficient, accurate, and suitable for the design purposes of electrical machines.reviewe

Inclusion of hysteresis and eddy current losses in dynamic induction machine models

This paper proposes a method for including both hysteresis losses and eddy current losses in the dynamic space vector model of induction machines. The losses caused by the rotation and magnitude changes of the flux vector are taken into account. The model can be applied, for example, to time-domain simulations and real-time applications such as drive control. Finite element analysis, simulations, and laboratory experiments of a 45-kW motor are used for the investigation. It is shown that the model can predict the iron losses in a wide frequency range. The accuracy is significantly improved as compared to earlier models.Peer reviewe

Bizerte

Des origines à la fin du XIXe siècle (El Briga) Le site actuellement occupé par la ville de Bizerte (Benzert) fut à l’époque romaine celui d’Hippo Diarrythus. Cette ville, fondée peut être avant Carthage, semble avoir été citée pour la première fois par Hécatée de Milet (VIe-Ve siècle). De siècle en siècle, le Périple dit de Scylax, entre 360 et 330 av. J.-C, Polybe, puis Diodore de Sicile mentionnent la ville sous le nom d’Hippou Akra à l’occasion d’événements historiques importants : expédi..

Comprehensive analysis of Lenz effect on the artificial heart valves during magnetic resonance imaging

This work presents results of a comprehensive analysis of the Lenz effect due to motion of artificial heart valves during magnetic resonance imaging. The interaction of rotating metallic heart valves with magnetic fields is studied by performing a time-domain analysis of the corresponding electromagnetic problem. We applied the finite element method (FEM) to solve the T - Omega formulation of Maxwell equations in two cases: first, for metallic disks located in the high intensity homogenous field of the magnet iso-center, and second, disks located in the non-uniform fringe field of the bore entrance. We showed that for valves with full solid disks (such as Starr-Edwards 6500) located in the magnet iso-center, the magnitude of adverse forces can be comparable to the forces applied by the beating heart. However, for rings which consist of multiply connected conductive regions, skin effect and proximity effect counteract, which leads to a diminished magnetic force. Results of this study show that mechanical heart valves with strengthening rings may be considered safe even under ultra-high imaging conditions with field intensities as high as 10 T. However, heart valves with full conducting disks should be considered as a contraindication to MR imaging

Hydrogeochemical and stable isotope data of groundwater of a multi-aquifer system: Northern Gafsa basin – Central Tunisia

The hydrodynamic of the multi-aquifer system (the Continental Intercalaire “ C.I ” and the Complex Terminal “ C.T ”) of the North Gafsa basin is largely determined by tectonics (Tebessa - Gafsa fault). The composition of groundwater is controlled by complex reactions at gas-liquid-solid “mineralogical composition of associated rocks” interfaces, which depend on the natural surrounding and potential anthropogenic impact. The hydrochemical data (major ion geochemistry) indicate that these groundwaters are characterized by the dominance a Ca-Mg-HCO3/SO4 and Na-Cl-NO3 water types. Geochemical pattern is mainly controlled by the dissolution of halite, gypsum and/or anhydrite as well as by the incongruent dissolution of carbonate minerals. The pH of these samples range from 6.54 to 8.89, supporting the conclusion that the H2CO3/HCO3 couple control pH buffering. Oxygen-18 (δ18O‰SMOW) and deuterium (dD‰SMOW) isotopic data show the exchange between the groundwater and the rock (water-rock interaction) and the evaporation effect. The isotopic content of the boreholes waters is of mixed Mediterranean - Atlantic origin and is opposite to the quantity of rainwater distribution, both in space and time in the study area. This is due to its geographical situation in the southern and south-western of the Mediterranean Sea and between the Atlas area and the Sahara Platform. The concentrations of the isotopic composition of the groundwater are significantly higher than the rainwater. This is indicative of the dissolution of salts and other processes modifying the rainwater geochemical composition during infiltration into the vadose zone. The hydraulic interconnection of these components of the system has led to the evolution of these interesting groundwater types

Extracorporeal Membrane Oxygenation for Severe Acute Respiratory Distress Syndrome associated with COVID-19: An Emulated Target Trial Analysis.

RATIONALE: Whether COVID patients may benefit from extracorporeal membrane oxygenation (ECMO) compared with conventional invasive mechanical ventilation (IMV) remains unknown. OBJECTIVES: To estimate the effect of ECMO on 90-Day mortality vs IMV only Methods: Among 4,244 critically ill adult patients with COVID-19 included in a multicenter cohort study, we emulated a target trial comparing the treatment strategies of initiating ECMO vs. no ECMO within 7 days of IMV in patients with severe acute respiratory distress syndrome (PaO2/FiO2 <80 or PaCO2 ≥60 mmHg). We controlled for confounding using a multivariable Cox model based on predefined variables. MAIN RESULTS: 1,235 patients met the full eligibility criteria for the emulated trial, among whom 164 patients initiated ECMO. The ECMO strategy had a higher survival probability at Day-7 from the onset of eligibility criteria (87% vs 83%, risk difference: 4%, 95% CI 0;9%) which decreased during follow-up (survival at Day-90: 63% vs 65%, risk difference: -2%, 95% CI -10;5%). However, ECMO was associated with higher survival when performed in high-volume ECMO centers or in regions where a specific ECMO network organization was set up to handle high demand, and when initiated within the first 4 days of MV and in profoundly hypoxemic patients. CONCLUSIONS: In an emulated trial based on a nationwide COVID-19 cohort, we found differential survival over time of an ECMO compared with a no-ECMO strategy. However, ECMO was consistently associated with better outcomes when performed in high-volume centers and in regions with ECMO capacities specifically organized to handle high demand. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/)