1,720,986 research outputs found
Aqueous uranium activity removal by CoFe2O4 nanoparticles
No full textCobalt ferrite (CoFe2O4) nanoparticles have been prepared by the method of spraying-co-precipitation. The advantages of this approach are high productivity, excellent repeatability and high magnetic performances of the fabricated materials. The obtained materials were characterized by different techniques as X-ray diffraction, transmission electron microscopy, scanning electron microscopy. It was shown that CoFe2O4 has the face-centered cubic trevorite structure and particle size of about 18 nm. The vibrating sample magnetometer measurement had shown that obtained material had saturation magnetization of about 40 emu/g, remanences was 14 emu/g, and coercive forces (Hc) was 0.9 kOe. An investigation of uranium adsorption onto CoFe2O4 magnetic nanoparticles was studied in this research. This was confirmed by our experimental results using the method of inductively coupled plasma mass spectrometry. The pH effect, adsorption kinetics, and adsorption isotherms were examined in batch experiments. The sorption isotherm agreed well with the Langmuir model, having a maximum sorption capacity of 53.36 mg/g at pH = 6 and T = 298 K. Present research might eventually lead to a simple and low-cost method for fabricating magnetic materials and application for efficient removal of uranium from aqueous solution.(Copied from article
Modèle simplifié pour les chaussées fissurées multicouches
No full textMost of design pavement models can not be used to simulate cracking in pavements. This problem can be modelled by using 3D finite element methods, but such calculations can be very time-consuming. In the objective to build a software for the evaluation of cracked pavements, and design solution for rehabilitation, we propose here to use a simplified plate model for bending problem linked to the Boussinesq model for the soil. The complete algorithm is programmed in the Matlab software. This model gives, very quickly, good approximations of the design stress fields near interfaces and vertical cracks in comparison with 3D finite element calculations. Thermal and shrinkage problem are studied and validated. In the aim to simulate some fatigue problems, a method is presented to accelerate the calculations.Les modèles simplifiés usuels de dimensionnement des chaussées ne permettent pas de modéliser des chaussées fissurées et une modélisation par éléments finis 3D peut s'avérer très lourde. Dans l'objectif de construire un outil rapide et efficace de diagnostic et d'entretien des chaussées dégradées par le trafic, un modèle simplifié est proposé. Ce modèle repose sur un modèle simplifié adapté aux problèmes de flexion, le modèle multiparticulaire des matériaux multicouches (M4) à 5n équations (n: nombre total de couches) et le modèle élastique de Boussinesq pour le massif de sol. Programmé sous Matlab, dans le cas de bicouches de chaussées fissurées verticalement, ce modèle donne très rapidement d'excellents résultats par comparaison avec des calculs éléments finis 3D. Les cas de chargement de retrait thermique et de gradient thermique sont intégrés dans la modélisation et validés. Pour accélérer encore plus l'obtention des solutions dans le cadre de calculs multi- cycles, une méthode d'extrapolation des résultats du 2D pour estimer le 3D est exposée
STUDY ON INFLUENCE OF TEMPERATURE AND DURATION OF HYDROTHERMAL TREATMENT TO PROPERTIES OF NANO FERRITE NiFe2O4 MATERIALS
No full textNiFe2O4 superparamagnetic nanoparticles have been prepared by the method of spraying - co-precipitation subsequent by hydrothermal treatment. This procedure allowed to produce efficiently nanoparticles with high performances. Different techniques such as XRD, TEM, EDX, VSM were used to investigate the morphology, structure and magnetic properties of the obtained materials. It is shown that the materials have face-centered cubic trevorite structure, and their degree of crystallinity and magnetic properties improved with increasing temperature and time of hydrothermal treatment. After 32 hours of hydrothermal treatment at 160°C, NiFe2O4 nanomaterial has particle size of about 23 nm and saturation magnetization (Ms) of 49 emu/g.</jats:p
Modèle simplifié pour les chaussées fissurées multicouches
No full textMost of design pavement models can not be used to simulate cracking in pavements. This problem can be modelled by using 3D finite element methods, but such calculations can be very time-consuming. In the objective to build a software for the evaluation of cracked pavements, and design solution for rehabilitation, we propose here to use a simplified plate model for bending problem linked to the Boussinesq model for the soil. The complete algorithm is programmed in the Matlab software. This model gives, very quickly, good approximations of the design stress fields near interfaces and vertical cracks in comparison with 3D finite element calculations. Thermal and shrinkage problem are studied and validated. In the aim to simulate some fatigue problems, a method is presented to accelerate the calculations.Les modèles simplifiés usuels de dimensionnement des chaussées ne permettent pas de modéliser des chaussées fissurées et une modélisation par éléments finis 3D peut s'avérer très lourde. Dans l'objectif de construire un outil rapide et efficace de diagnostic et d'entretien des chaussées dégradées par le trafic, un modèle simplifié est proposé. Ce modèle repose sur un modèle simplifié adapté aux problèmes de flexion, le modèle multiparticulaire des matériaux multicouches (M4) à 5n équations (n: nombre total de couches) et le modèle élastique de Boussinesq pour le massif de sol. Programmé sous Matlab, dans le cas de bicouches de chaussées fissurées verticalement, ce modèle donne très rapidement d'excellents résultats par comparaison avec des calculs éléments finis 3D. Les cas de chargement de retrait thermique et de gradient thermique sont intégrés dans la modélisation et validés. Pour accélérer encore plus l'obtention des solutions dans le cadre de calculs multi- cycles, une méthode d'extrapolation des résultats du 2D pour estimer le 3D est exposée
ADSORPTION OF URANIUM FROM AQUEOUS SOLUTION BY Cu0.5Ni0.5Fe2O4 – REDUCED GRAPHENE OXIDE NANOCOMPOSITES
No full textCu0.5Ni0.5Fe2O4 – reduced graphene oxide composites (CNF-rGO) as an efficient adsorbent for the adsorption of uranium (VI) have been synthesized by a two-steps methods. The structures and the physicochemical properties of adsorbents are characterized by Scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy (RAMAN) and Vibrating sample magnetometer (VSM) measurement. It was found that rGO were exfoliated and decorated homogeneously with CNF nanoparticles having diameters of 20 nm. The saturated magnetization (Ms) value was estimated to be 60 emu/g, remanences (Mr) and coercive forces (Hc) near to zero, indicating that obtained material is superparamagnetic. The pH effect, contact time and adsorption isotherms were examined in batch experiments. The adsorption isotherm agreed well with the Langmuir model, having a maximum adsorption capacity of 256 mg/g, at pH = 6, T = 298 K.</jats:p
Modèle simplifié pour les chaussées fissurées multicouches
No full textMARNE-LA-VALLEE-ENPC-BIBL. (774682303) / SudocSudocFranceF
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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