1,721,053 research outputs found
Modelling the self-healing potential of dissoluble encapsulated cement
No full textIn its fresh state, cementitious systems can be considered as colloidal suspensions build up from a mineral particles that follow a predefined grading. In this paper, a modelling approach that shows the healing potential of a blended cementitious system will be provided that consists of original cementitious particles mixed with so-called Dissoluble Encapsulated Particles (DEPs). DEPs are represented by a range of predefined fractions of original cementitious particles, but with its surface covered with a thin membrane. The self-healing principle of this system is based on the most basic healing process, where a delayed hydration of the DEP fractions may occur initiated by a crack. The crack actually triggers the membrane to open and exposes the still unhydrated DEP particles to water, after which the delayed hydration of the DEP system will take place, while closing the crack. The proposed model will demonstrate the healing potential of DEP inside a concrete and analyse the most dominant parameters affecting the mechanism. The membrane is considered to decapsulate by it's dissolution or cracking whenever being triggered by cementitious crack formation, which either lowers pH-conditions due increased CO2 ingress, or induces mechanical stresses. The results show the potential of the healing mechanism to bridge a certain crack width, and shows, which fractions of a regular cement should be replaced in order the DEP system being most efficient. The numerical predictions also show that multi fraction DEP systems are more efficient then single fraction DEP, and that the addition of DEP does not affect the properties but may lead to a delay in the property development of cementitious systems
A phase-field approach for portlandite carbonation and application to self-healing cementitious materials
No full textA conceptual phase-field model is proposed for simulating complex microstructural evolutions during the self-healing process of cementitious materials. This model specifically considers carbonation healing mechanisms activated by means of dissolution of soluble Ca(OH)₂ mineral and precipitation of the CaCO₃ self-healing product. The system is described by a set of conservative and non-conservative field variables based on a thermodynamic analysis of the precipitation process and realised numerically using the finite element method (FEM). As a novel concept for modeling self-healing of cementitious materials, the evolution of multiple interfaces was investigated and demonstrated on a simple experimental test case of a self-healing mechanism consisting of carbonating calcium hydroxide. Parametric studies were performed to numerically investigate the effect of chemo-physical conditions. Two representative practical examples of cementitious materials were numerically implemented. It is demonstrated that the simulated evolution of the crack morphology is in good qualitative agreement with the experimental data
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
Hydrating Cement Particle Interaction Model for Yield Stress Analysis
No full textThis study overviews existing methods for analyzing cement paste yield stress, and presents a new approach based on micro-structural computation. The proposed model explicitly considers cement particle interactions, both the colloidal and the nucleated gel ones. A new algorithm is proposed based on flocculating of poly-dispersed hard spheres in a simulation box, followed by nucleation of mono-sized nano-gel particles. The obtained virtual microstructures are than used as an input for a mechanical approach, which is conceptualized for simulating sliding kinematics needed to initiate the flow of the percolated solid network, i.e. to reach the paste yield stress. The microstructural modeling tool provides insights on how the localized gel is bridging the cement particles, responsible for the yield stress properties of bulk cement paste. Thus, it provides a promising new approach for quantifying the evolution of the bridging strength with nucleation (shear rest) time, enabling parametrization of the mechanical yield stress computation at micro-structural scale
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
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