496 research outputs found

    Some remarks on Hermitian manifolds satisfying KĂ€hler-like conditions

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    We study Hermitian metrics whose Bismut connection ∇ B satisfies the first Bianchi identity in relation to the SKT condition and the parallelism of the torsion of the Bimut connection. We obtain a characterization of complex surfaces admitting Hermitian metrics whose Bismut connection satisfy the first Bianchi identity and the condition RB(x, y, z, w) = RB(Jx, Jy, z, w) , for every tangent vectors x, y, z, w, in terms of Vaisman metrics. These conditions, also called Bismut KĂ€hler-like, have been recently studied in Angella et al. (Commun Anal Geom, to appear, 2018), Yau et al. (2019) and Zhao and Zheng (2019). Using the characterization of SKT almost abelian Lie groups in Arroyo and Lafuente (Proc Lond Math Soc (3) 119:266–289, 2019), we construct new examples of Hermitian manifolds satisfying the Bismut KĂ€hler-like condition. Moreover, we prove some results in relation to the pluriclosed flow on complex surfaces and on almost abelian Lie groups. In particular, we show that, if the initial metric has constant scalar curvature, then the pluriclosed flow preserves the Vaisman condition on complex surfaces

    L’innovation pĂ©dagogique vue de l’intĂ©rieure

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    Cet article vise Ă  souligner l’importance de l’ethnographie de l’éducation comme outil pour comprendre et dĂ©crire de maniĂšre critique les pratiques pĂ©dagogiques innovatrices qui ne prennent du sens que lorsqu’elles sont envisagĂ©es Ă  partir de l’intĂ©rieur, c’est-Ă -dire du point de vue de leurs praticiens. D’autre part, elle fait le compte-rendu de l’extension de cette mĂ©thode d’analyse de l’école, Ă  travers les programmes de Master et de Doctorat de Sciences de l’Education, dans la spĂ©cialitĂ© d’Innovation PĂ©dagogique de l’UniversitĂ© de MadĂšre et son Centre de Recherche en Education (CIE-UMa), qui se dĂ©roulent Ă  MadĂšre, Ă  SantarĂ©m (prĂšs de Lisbonne) et au BrĂ©sil (dans les villes de BrasĂ­lia, SĂŁo Luis do MaranhĂŁo, Salvador, IbicaraĂ­, Feira de Santana, Recife et Fortaleza) et qui intĂšgrent une bonne partie de la pensĂ©e ethnographique de Lapassade, parmi d’ autres auteurs. Finalement, la communication tĂ©moigne de notre hommage en forme d’action Ă  la contribution scientifique de Georges Lapassade

    BEST Cities: Software User Guide

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    The Benchmarking and Energy-Saving Tool for Low Carbon Cities (BEST Cities) is a dynamic decision-making tool, designed to assist local policy makers and urban planners in prioritizing strategies for energy and carbon saving at the city level in China. China’s 12th Five-Year Plan (2011-2015) targets a reduction in carbon intensity of the economy (CO2 emissions per unit of GDP) by 17%. In the Low Carbon Development 2014-2015 energy saving action plan, the State Council calls for interim targets of more than 4% in 2014 and more than 3.5% in 2015. The State Council also calls for energy intensity saving (energy consumption per unit of GDP) of more than 3.9% per year for 2014 and 2015. The longer-term goal is to reduce carbon intensity by 40-45% from 2005 to 2020. With targets for low-carbon development featuring prominently in the 12th FYP and longer-term planning, cities must determine how to meet targets and promote a climate-friendly city. The BEST Cities tool can help

    Development of an End-Use Sector-Based Low-Carbon Indicator System for Cities in China

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    In 2009, China committed to reducing its carbon dioxide intensity (CO2/unit of gross domestic product, GDP) by 40 to 45 percent by 2020 from a 2005 baseline. In March 2011, China’s 12th Five-Year Plan established a carbon intensity reduction goal of 17% between 2011 and 2015. China’s National Development and Reform Commission (NDRC) then announced the selection of five provinces and eight cities to pilot low carbon development work. Macro-level indicators of low carbon development, such as energy use or CO2 emissions per unit of GDP or per capita may be too aggregated to be meaningful measurements of whether a city or province is truly “low carbon”. Instead, indicators based on energy end-use sectors (industry, residential, commercial, transport) offer a better approach for defining “low carbon” and for taking action to reduce energy-related carbon emissions. This paper presents and tests a methodology for the development of an end-use sectorbased low-carbon indicator system at the city level, providing initial results for an end-use low carbon indicator system based on data available at the municipal levels. The paper consists of a discussion of macro-level indicators that are typically used for inter-city, regional, or intercountry comparisons; the methodology used to develop a more robust low carbon indicator system for China; and the results of this indicator system. The research concludes with a discussion of issues encountered during the development of the end-use sector-based low-carbon indicator, followed by recommendations for future improvement

    CDMA, OFDM, MC-CDMA, quel choix pour une voie descendante ?

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    Cet article propose une démarche comparative de différentes formes d'onde candidates pour une voie descendante de radiocommunications. Partant d'un formalisme général pour le DS-CDMA, l'OFDM et le MC-CDMA, les comportements de ces formes d'onde vis à vis d'erreurs de fréquence ou de bruit de phase sont analysés

    Catalytic Oxidation of Soot and Volatile Organic Compounds over Cu and Fe Doped Manganese Oxides Prepared via Sol-Gel Synthesis

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    A set of manganese oxide catalysts was synthesized and doped with Cu and/or Fe by means of the citric acid sol-gel preparation method. The samples were studied by means of several characterization techniques: field-emission scanning electron microscopy (FESEM), X-ray powder diffraction (XRD), N2-physisorption at -196 °C, H2 and soot temperature-programmed reduction (H2-TPR, soot-TPR) and X-ray photoelectron spectroscopy (XPS). The catalytic performance of the prepared catalysts was investigated in the oxidation of a probe VOC molecule (propylene) and carbon soot singularly and simultaneously. The catalytic performances were studied as well assuring a content of 5 vol.% of water in the gaseous reactive mix. The investigations evidenced that the best soot catalytic oxidation rates occurred over the Mn2O3 sample, while the copper-doped manganese oxide (i.e. the MnCu15) showed the best performance in the decomposition of propylene. The soot conversion rates of the samples were positively correlated to the Mn3+/Mn2+ ratio of the samples, while the activity in the oxidation of propylene could be attributed to the reducibility enhancement caused by the insertion of Cu species in the structure of Mn2O3. The most active samples in soot oxidation demonstrated only a slight catalytic activity deactivation after thermal aging and practically no deactivation during the tests with humidity. Interestingly, the simultaneous soot-propylene oxidation tests evidenced an enhancement of the oxidation of soot particles in "tight"contact with the catalyst, likely due to a cooperative effect between soot and propylene oxidation

    Cortical activity during walking and balance tasks in older adults and in people with Parkinson’s disease: a structured review

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    An emerging body of literature has examined cortical activity during walking and balance tasks in older adults and in people with Parkinson’s disease, specifically using functional near infrared spectroscopy (fNIRS) or electroencephalography (EEG). This review provides an overview of this developing area, and examines the disease-specific mechanisms underlying walking or balance deficits. Medline, PubMed, PsychInfo and Scopus databases were searched. Articles that described cortical activity during walking and balance tasks in older adults and in those with PD were screened by the reviewers. Thirty-seven full-text articles were included for review, following an initial yield of 566 studies. This review summarizes study findings, where increased cortical activity appears to be required for older adults and further for participants with PD to perform walking and balance tasks, but specific activation patterns vary with the demands of the particular task. Studies attributed cortical activation to compensatory mechanisms for underlying age- or PD-related deficits in automatic movement control. However, a lack of standardization within the reviewed studies was evident from the wide range of study protocols, instruments, regions of interest, outcomes and interpretation of outcomes that were reported. Unstandardized data collection, processing and reporting limited the clinical relevance and interpretation of study findings. Future work to standardize approaches to the measurement of cortical activity during walking and balance tasks in older adults and people with PD with fNIRS and EEG systems is needed, which will allow direct comparison of results and ensure robust data collection/reporting. Based on the reviewed articles we provide clinical and future research recommendations

    Catalytic Abatement of Volatile Organic Compounds and Soot over Manganese Oxide Catalysts

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    A set of manganese oxide catalysts was synthesized via two preparation techniques: solution combustion synthesis (Mn3O4/Mn2O3-SCS and Mn2O3-SCS) and sol-gel synthesis (Mn2O3-SG550 and Mn2O3-SG650). The physicochemical properties of the catalysts were studied by means of N2-physisorption at −196◩ C, X-ray powder diffraction, H2 temperature-programmed reduction (H2-TPR), soot-TPR, X-ray photoelectron spectroscopy (XPS) and field-emission scanning electron microscopy (FESEM). The high catalytic performance of the catalysts was verified in the oxidation of Volatile Organic Compounds (VOC) probe molecules (ethene and propene) and carbon soot in a temperature-programmed oxidation setup. The best catalytic performances in soot abatement were observed for the Mn2O3-SG550 and the Mn3O4/Mn2O3-SCS catalysts. The catalytic activity in VOC total oxidation was effectively correlated to the enhanced low-temperature reducibility of the catalysts and the abundant surface Oα-species. Likewise, low-temperature oxidation of soot in tight contact occurred over the Mn2O3-SG550 catalyst and was attributed to high amounts of surface Oα-species and better surface reducibility. For the soot oxidation in loose contact, the improved catalytic performance of the Mn3O4/Mn2O3-SCS catalyst was attributed to the beneficial effects of both the morphological structure that—like a filter—enhanced the capture of soot particles and to a probable high amount of surface acid-sites, which is characteristic of Mn3O4 catalysts
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