317 research outputs found

    Symmetric intersections of Rauzy fractals

    Full text link
    In this article we study symmetric subsets of Rauzy fractals of unimodular irreducible Pisot substitutions. The symmetry considered is reflection through the origin. Given an unimodular irreducible Pisot substitution, we consider the intersection of its Rauzy fractal with the Rauzy fractal of the reverse substitution. This set is symmetric and it is obtained by the balanced pair algorithm associated with both substitutions

    Design of a high-torque machine with two integrated motors axes reducing the electric vehicle consumption

    Get PDF
    The motorization of electric vehicle needs to work at a constant power on a wide range of speed. In order to be able to satisfy these requirements, we describe in this paper a solution, which consists in modifying of a simple structure of a permanent magnet motor by a double rotor structure integrating two motor axes into the same machine. This article describes, then, a design methodology of a permanent magnet motor with double rotor, radial flux, and strong starting torque for electric vehicles. This work consists on the analytical dimensioning of the motor by taking into account several operation constraints followed by a modelling by the finite elements method. This study is followed by the comparison between this motor and a motor with one rotor. A global model of the motor- converter is developed for the purpose to answer several optimisation problem

    Pragmatic Ontology Evolution: Reconciling User Requirements and Application Performance

    Get PDF
    Increasingly, organizations are adopting ontologies to describe their large catalogues of items. These ontologies need to evolve regularly in response to changes in the domain and the emergence of new requirements. An important step of this process is the selection of candidate concepts to include in the new version of the ontology. This operation needs to take into account a variety of factors and in particular reconcile user requirements and application performance. Current ontology evolution methods focus either on ranking concepts according to their relevance or on preserving compatibility with existing applications. However, they do not take in consideration the impact of the ontology evolution process on the performance of computational tasks – e.g., in this work we focus on instance tagging, similarity computation, generation of recommendations, and data clustering. In this paper, we propose the Pragmatic Ontology Evolution (POE) framework, a novel approach for selecting from a group of candidates a set of concepts able to produce a new version of a given ontology that i) is consistent with the a set of user requirements (e.g., max number of concepts in the ontology), ii) is parametrised with respect to a number of dimensions (e.g., topological considerations), and iii) effectively supports relevant computational tasks. Our approach also supports users in navigating the space of possible solutions by showing how certain choices, such as limiting the number of concepts or privileging trendy concepts rather than historical ones, would reflect on the application performance. An evaluation of POE on the real-world scenario of the evolving Springer Nature taxonomy for editorial classification yielded excellent results, demonstrating a significant improvement over alternative approaches

    Trace element contamination in the mine-affected stream sediments of Oued Rarai in north-western Tunisia. A river basin scale assessment

    Get PDF
    High-quality and accurate environmental investigations are essential for the evaluation of contamination and subsequent decision-making processes. A combination of environmental geochemical indices, multivariate analyses and geographic information system approach was successfully used to assess contamination status and source apportionment of trace elements (Ag, As, Cd, Cr, Cu, Hg, Ni, Pb, Sb, V and Zn) in surface stream sediments from the Oued Rarai basin in north-western Tunisia, containing various metal and metalloid ores. The contamination level reported in this study indicates a non-negligible potential ecological risk, mainly related to sediment transport along the river. Antimony (concentrations ranged from 0.02 to 297 mg kg−1 and Igeo > 5), arsenic (from 0.5 to 1490 mg kg−1 and Igeo > 5), lead (from 2.9 to 5150 mg kg−1 and Igeo > 5) mercury (from 0.05 to 54.4 mg kg−1 and Igeo > 5) and silver (from 0.05 to 9.4 mg kg−1 and Igeo > 5) showed the most crucial contamination. Besides, potential ecological risk index values were maximum for arsenic with a median of 302, indicating a very high to serious ecological risk (> 160). Results from correlation analysis and principal component analysis revealed three main geochemical associations related to lithologic, tectonic and anthropogenic sources. V, Cr and Cu mainly originated from natural bedrock and soil. Ag and Cd were more controlled by both natural and mining enrichments. Mercury and Pb were mostly influenced by the ancient ore-related activities at the Oued Rarai site and north-east–south-west trending faults. Finally, Sb, As, Ni and Zn were largely controlled by the siliciclastic continental Neogene sequences. Finally, the physical and chemical dynamics of the watershed system, lithological properties, mineralisation, tectonic settings and mobilisation of subsurface sediments largely controlled both concentrations and spatial patterns of trace elements in the study basin. These results need to be considered in the strategies of suitable environmental management at former and current mining sites in north-western Tunisia

    La maladie de cowden a propos d’un cas

    Get PDF
    La maladie de Cowden est une maladie hĂ©rĂ©ditaire Ă  transmission autosomique dominante caractĂ©risĂ©e par des lĂ©sions associant des atteintes cutanĂ©es constantes et caractĂ©ristiques (lĂ©sions papuleuses au niveau de la face et des extrĂ©mitĂ©s) et des lĂ©sions viscĂ©rales inconstantes notamment thyroĂŻdiennes, mammaires, intestinales et rĂ©nales Ă  haut risque de dĂ©gĂ©nĂ©rescence. Nous rapportons un cas chez une femme de 30 ans porteuse d’une craniomĂ©galie, de polypes intestinaux, d’un fibroadĂ©nome des seins, de lĂ©sions papuleuses des gencives et d’un goitre multi-nodulaire. Elle a eu dans notre service une thyroĂŻdectomie totale dont l’analyse anatomopathologique dĂ©finitive de la piĂšce a rĂ©vĂ©lĂ© un micro-carcinome vĂ©siculaire du lobe gauche de la thyroĂŻde. Les lĂ©sions thyroĂŻdiennes sont habituellement bien limitĂ©es, mais devant la multifocalitĂ©, le risque accru de rĂ©cidive et de dĂ©gĂ©nĂ©rescence maligne, une thyroĂŻdectomie totale doit ĂȘtre prĂ©conisĂ©e.Mots clĂšs : Maladie de Cowden, Cancer de la thyro

    A Comparative Study of Permanent Magnet Motor Cost Minimization Dedicated to Electric Traction JES Journal of Electrical Systems

    Get PDF
    In this paper, we present a permanent magnet motor cost minimization dedicated to the electric traction based on a genetic algorithms (GAs) method. Our objective is to minimize this cost by taking account of certain constraints. The choice of a suitable coding is a critical element which depends largely on the genetic algorithm effectiveness. That is why we present a comparative study between two types of genetic algorithms i.e. a binary coded genetic algorithm (BCGA) and a real coded genetic algorithm (RCGA)

    A blend of Traditional Visual Symbols in BIPV application; any Prospects?

    Get PDF
    Traditional Visual symbols are of great relevance, especially within the architectural space. Buildings may adopt symbols to depict culture, iconicity or identity. The quest to meet sustainable building targets and avert the looming effects of climate change has brought about renewable options such as Building Integrated Photovoltaics (BIPV), which is the use of solar PVs to replace conventional building materials such that they form part of the building envelope. This paper discusses the nexus between traditional visual symbols and BIPV application. A hypothetical question is posed; will incorporating visual symbols in BIPV design influence its adoption? Although a detailed evidence-based result is not produced in this paper , architectural visualisation is used to depict the outlook of traditional Ghanaian symbols in BIPV application, while further studies is being conducted into the prospects of these symbols in BIPVs design using Traditional Ghanaian "Adinkra" symbols as case study
    • 

    corecore