1,721,044 research outputs found
The Effect of Relative Humidity on Creep Behavior of Cement Paste Microprism
No full textDespite decades of extensive studies, the mechanism of concrete creep remains a subject of debate, mainly due to the complex nature of cement microstructure. This complexity is further amplified by the interplay between water and the cement microstructure. The present study aimed to better understand the creep mechanism through creep tests on microprisms of cement paste at hygral equilibrium. First, microprisms with dimensions of 150 mm x 150 mm x 300 mm were prepared by precision cutting from a cement paste specimen with a water-to-cement ratio of 0.4. Subsequently, uniaxial compression and creep tests were carried out on these microprisms in a chamber with controlled relative humidity (RH). To mitigate the impact of plasticity and damage, the applied peak load was set to generate a stress level that was approximately 40% of the compressive strength. Moreover, an analytical coefficient phi was formulated to account for the foundation effect on microprism creep, agreeing with the numerical analysis employing the finite element method. Our findings showed that the microscale creep compliance varied when the RH level was changed from 90% to 11%. Furthermore, logarithmic and power-law models were both applied to simulate creep curves. Lastly, the modeled creep behaviors were compared with those obtained by microindentation experiments in previous studies
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Nanoindentation relaxation study and micromechanics of Cement-Based Materials
No full textCe travail évalue le comportement mécanique des matériaux cimentaires à différentes échelles de distance. Premièrement, les propriétés mécaniques du béton produit avec un bioplastifiant à base de microorganismes efficaces (EM) sont etudiées par nanoindentation statistique, et comparées aux propriétés mécaniques du béton produit avec un superplastifiant ordinaire (SP). Il est trouvé que l’ajout de bioplastifiant à base de produit EM améliore la résistance des C–S–H en augmentant la cohésion et la friction des nanograins solides. L’analyse statistique des résultats d’indentation suggère que le bioplastifiant à base de produit EM inhibe la précipitation des C–S–H avec une plus grande fraction volumique solide. Deuxièmement, un modèle multi-échelles à base micromécanique est dérivé pour le comportement poroélastique de la pâte de ciment au jeune age. L’approche proposée permet d’obtenir les propriétés poroélastiques requises pour la modélisation du comportoment mécanique partiellement saturé des pâtes de ciment viellissantes. Il est montré que ce modèle prédit le seuil de percolation et le module de Young non drainé de façon conforme aux données expérimentales. Un metamodèle stochastique est construit sur la base du chaos polynomial pour propager l’incertitude des paramètres du modèle à travers plusieurs échelles de distance. Une analyse de sensibilité est conduite par post-traitement du metamodèle pour des pâtes de ciment avec ratios d’eau sur ciment entre 0.35 et 0.70. Il est trouvé que l’incertitude sous-jacente des propriétés poroélastiques équivalentes est principalement due à l’énergie d’activation des aluminates de calcium au jeune age et, plus tard, au module élastique des silicates de calcium hydratés de basse densité.This work assesses the mechanical behavior of cement-based materials through different length scales. First, the mechanical properties of concrete produced with effective microorganisms (EM)-based bioplasticizer are investigated by means of statistical nanoindentation, and compared to the nanomechanical properties of concrete produced with ordinary superplasticizer (SP). It is found that the addition of EM-based bioplasticizer improves the strength of C–S–H by enhancing the cohesion and friction of solid nanograins. The statistical analysis of indentation results also suggests that EM-based bioplasticizer inhibits the precipitation of C–S–H of higher density. Second, a multiscale micromechanics-based model is derived for the poroelastic behavior of cement paste at early age. The proposed approach provides poroelastic properties required to model the behavior of partially saturated aging cement pastes. It is shown that the model predicts the percolation threshold and undrained elastic modulus in good agreement with experimental data. A stochastic metamodel is constructed using polynomial chaos expansions to propagate the uncertainty of the model parameters through different length scales. A sensitivity analysis is conducted by post-treatment of the meta-model for water-to-cement ratios between 0.35 and 0.70. It is found that the underlying uncertainty of the effective poroelastic proporties is mostly due to the apparent activation energy of calcium aluminate at early age and, later on, to the elastic modulus of low density calcium-silicate-hydrate
Développement des structures composites bois-béton avec emphase sur le comportement de la connexion
No full textLes charpentes de bois sont une alternative très intéressante pour la construction de bâtiments multiétages. Grâce à sa faible empreinte écologique, ses excellentes propriétés mécaniques et l’esthétisme de son produit fini, le bois est un matériau incontournable. En y ajoutant une mince dalle de béton collaborant, on permet de réduire considérablement l’épaisseur et le poids des planchers tout en respectant les critères de conception. Pour ce faire, le transfert des charges de la dalle de béton à la poutre de bois doit passer par les connecteurs. Différents types de connecteurs permettent ce transfert. Néanmoins, il est difficile de garantir un comportement rigide en service et une rupture ductile de la poutre. La ductilité du connecteur est un indicatif de l’aptitude de la structure à dissiper de l’énergie. Dans ce mémoire, le comportement d’un nouveau connecteur composite coulé en place sera décortiqué. Ce connecteur en béton fibré à ultra-haute performance (BFUP) et contenant un coeur en acier permet de garantir la rigidité et la ductilité. L’objectif de cette recherche est de vérifier et de valider le comportement du connecteur composite en variant les différents paramètres géométriques, soit le diamètre et la longueur. De plus, afin de confirmer la performance du nouveau connecteur, un essai de flexion sera réalisé sur des poutres de plancher type en comparaison avec un autre type de connecteur. Ces essais en laboratoire seront également validés à l’aide de méthode de calcul simple et plus complexe permettant de vérifier le comportement structural en service et à l’ultime. Finalement, ce mémoire explore le comportement d’une mince dalle de BFUP connectée à une poutre de bois lamellé-collé (BLC) d’une portée de 9 m. Les poutres composites bois-béton ont été conçues avec une approche multicritère simplifiée. Les résultats confirment le potentiel prometteur, en termes de poids et d’épaisseur globale, de l’utilisation du BFUP dans les futurs projets de bâtiment multi-étagesTimber framing is a very attractive alternative for the construction of multistory buildings. Thanks to its low ecological footprint, its excellent mechanical properties and the aesthetics of finished product. By adding a thin concerted concrete slab, the thickness and weight of the floors can be considerably reduced while respecting the design criteria. In order to succeed, the load must be transferred from the concrete slab to the timber beam by the shear connectors. Different types of connectors allow this transfer. Nevertheless, it is difficult to guarantee good stiffness in serviceability and ductile behaviour before the collapse of the structure. Ductility is an indicator of the ability of the structure to dissipate energy. In this master thesis, the behaviour of a new cast-in-place composite connector will be discussed. This ultra-high performance fiber-reinforced concrete (UHPFRC) with a steel core ensures stiffness and ductility. The aim of this research is to verify and validate the behaviour of the composite connector by varying the different geometric parameters, namely the diameter and the length. Furthermore, in order to confirm the performance of the new connector, a bending test will be carried out on typical floor beams in comparison with another shear connector. These laboratory tests will also be validated using a simple and complex calculation method to verify the structural behaviour in both Serviceability Limit States (SLS) and Ultimate Limit States (ULS). Finally, this thesis explores the behaviour of a thin slab of UHPFRC connected to a glued laminated timber (GLT) with a long span of 9 m. The TCC beams were designed with a simplified multi-criteria approach. The results confirm the promising potentials, in terms of weight and overall thickness, of using UHPFRC thin slab for future TCC multistory buildings
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