1,720,984 research outputs found
Modeling hygro-thermal performance and strains of cementitious building materials maturing in variable conditions
No full textA novel model of hygro-thermal performance of cement-based building materials during their maturing, considering evolution of their strength properties and deformations (shrinkage and creep strains), described in terms of effective stress is briefly presented. Creep is described by means of the modified microprestress - solidification theory by Bazant et al., with some modifications to take into account the effects of temperature and relative humidity on the cement hydration. Shrinkage strains are modeled by using effective stresses in the form introduced by Gray and Schrefler, giving a good agreement with experimental data also for low values of relative humidity. Results of three numerical examples based on the real experimental tests are solved to validate the model. They demonstrate its possibilities to analyze both autogenous deformations in maturing cementitious materials, and creep and shrinkage phenomena, in building elements of different age, sealed or drying at various conditions
Modelling of autogenous hygro-thermal phenomena in massive concrete structures - a case study
No full textModeling of internal curing in maturing mortar
No full textPrediction of the influence of internal curing both on the material behavior during maturing and on its final physical properties is an important issue in concrete research. A novel, mechanistic-type numerical model of concrete is applied for modeling the chemo-physical phenomena taking place during internal curing. The model takes into account full coupling between chemo-thermal, hygral and mechanical phenomena in porous media (i.e., maturing cement paste or mortar). In this work, the recent development of the model for description of internal curing is presented along with the results of simulations. The model allows for description of the influence of internal curing on such phenomena as hydration, self-desiccation or autogenous shrinkage. The results of the simulations are compared with the experimental data concerning autogenous phenomena in low water-to-cement ratio mortars containing superabsorbent polymers
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
X-Ray Micro Tomography of Water Absorption by Superabsorbent Polymers in Mortar
Full text linkSuperabsorbent Polymers (SAP) have been recently subject of investigation as smart admixtures for cement-based materials. The properties of these polymers enable their use for internal curing, increasing freeze/thaw resistance, boosting autogenous self-healing and providing a crack self-sealing effect in cementitious composites. Except for the earliest application, the functioning of these beneficial effects invloves the absorption by the polymers of ingress water in the hardened cementitious matrix and later release, as well as their capacity to complete multiple absorption/desorption cycles. In this work, the absorption of water in mortar with superabsorbent polymers is monitored during the first 60 min of absorption through micro-CT. The experimental series included the presence of cracks. The registration and differentiation of sub-minute (18 s) scans enabled the individuation of bulk water content distribution in the mortar with a resolution of 55 μm. The swollen volume of SAP could also be quantified and studied in time. The results point out that although embedded SAP absorb water from the matrix, this absorption is slow and reduced with respect to water absorption during mixing for the used SAP. Same effect is observed for SAP in the cracks.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Materials and Environmen
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