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Modélisation 3D de la microstructure de la pâte cimentaire, guidée expérimentalement par des méthodes quantitatives multiéchelles
Get PDFAbstract: Concrete remains the most widely used construction material worldwide, and its performance is fundamentally governed by the properties of the hardened cement paste (HCP) matrix. At the microscale, this matrix is a highly heterogeneous and evolving material, composed of a complex mixture of hydration products, residual clinker, and pore networks. The morphology and spatial distribution of these phases critically influence both the mechanical and transport behavior of cementitious materials. Despite advances in experimental imaging and computational modeling, current multiscale modeling frameworks still struggle to integrate physically realistic 3D microstructures and validate their fidelity in a quantitative and reproducible manner.
This doctoral research addresses a fundamental challenge in micromechanical modeling of HCP: the disconnect between simplified numerical models and the morphological and chemical complexity of real microstructures. The objective is to develop and implement an integrated framework for generating, analyzing, and applying 3D microstructure-based models of cement paste, that combines hydration-based simulation, high-resolution X-ray microtomography (µ-CT) imaging, quantitative energy-dispersive X-ray spectroscopy (QEDS)-driven segmentation, and spatial statistical analysis. By integrating experimental and numerical data and applying descriptor-based validation, the work advances both the representativeness and reliability of microstructure-based simulations in cementitious systems. The framework is structured around three core contributions.
For the first contribution, digitally resolved 3D microstructures of Ordinary Portland Cement (OPC) paste were generated using the µiC hydration model. To ensure thermodynamic realism and accurately represent phase evolution, the model was calibrated against quantitative phase assemblage data derived from X-ray diffraction (XRD) and thermodynamic simulations using GEMS. The refined model captured not only major phases, such as C-S-H and portlandite, but also minor hydrates, and was able to simulate realistic voxelized geometries at submicron resolution, ready for micromechanical simulations.
The second contribution focuses on the experimental reconstruction of phase-labeled 3D microstructures using µ-CT imaging and a novel QEDS-supervised segmentation workflow. A hybrid image processing pipeline was developed to overcome the known limitations of grayscale overlap in µ-CT datasets. This pipeline integrates Block-Matching 4D (BM4D) denoising and sharpening, and Random Forest classification trained on co-registered QEDS maps and µ-CT datasets. The resulting segmentation process enabled reliable identification of critical phases such as ferrite, portlandite, and hydrates, even when their grayscale signatures significantly overlapped. This method was successfully extended to microcubes for micromechanical testing, providing phase-resolved digital volumes that preserve real boundary conditions, spatial heterogeneity, and particle-level information.
The third contribution introduces a spatial statistical framework for quantitatively comparing modeled and experimental microstructures. Descriptor functions including the two-point correlation function (S₂) and the lineal-path function (L) were computed on harmonized phase groups from both µiC and µ-CT datasets. A representative volume element (RVE) of 200 µm³ was selected based on phase fraction stability and particle size distribution convergence. Descriptor-based comparisons revealed key morphological differences, such as smoother gradients and lower pore connectivity in simulated microstructures, underscoring the value of experimental imaging for capturing topological realism. These comparisons support descriptor-based validation of hydration models and inform their applicability in micromechanical simulations.
Altogether, these contributions establish a robust and experimentally anchored modeling framework for cement paste that is statistically validated, morphologically realistic, and adaptable to multiscale mechanical studies. The research strengthens the bridge between numerical simulation and experimental reality and paves the way for more accurate predictive tools in the multiscale modeling of alternative cementitious materials.Le béton demeure le matériau de construction le plus utilisé à l’échelle mondiale, et ses performances sont fondamentalement déterminées par les propriétés de la matrice cimentaire durcie. À l’échelle microscopique, cette matrice constitue un matériau hautement hétérogène et évolutif, composé d’un mélange complexe de produits d’hydratation, de clinker résiduel et de réseaux poreux. La morphologie et la distribution spatiale de ces phases influencent de manière critique les comportements mécaniques et de transport des matériaux cimentaires. Malgré les progrès réalisés en imagerie expérimentale et en modélisation numérique, les cadres actuels de modélisation multiéchelle peinent encore à intégrer des microstructures 3D physiquement réalistes et à valider leur fidélité de manière quantitative et reproductible.
Cette recherche s’attaque à un défi fondamental de la modélisation micromécanique de la pâte de ciment durcie : le décalage persistant entre les modèles numériques simplifiés et la complexité morphologique et chimique des microstructures réelles. L’objectif est de développer et de mettre en œuvre un cadre unifié pour la modélisation de la microstructure 3D de la pâte de ciment, combinant la simulation de l’hydratation, une imagerie par microtomographie à rayons X à haute résolution, une segmentation guidée par spectroscopie à dispersion d'énergie quantitative des rayons X (QEDS), et une analyse statistique spatiale. En intégrant les données expérimentales et numériques, et en appliquant une validation basée sur des descripteurs statisiques de la microstructure, ce travail améliore à la fois la représentativité et la fiabilité des simulations basées sur la microstructure dans les systèmes cimentaires. Le cadre méthodologique s’articule autour de trois contributions principales.
La première contribution concerne la génération de microstructures 3D numériques de pâtes de ciment Portland ordinaire, à l’aide du modèle d’hydratation µiC. Afin de garantir le réalisme thermodynamique et de représenter fidèlement l’évolution des phases, ce modèle a été calibré à partir de données quantitatives issues de la diffraction des rayons X (QXRD) et de simulations thermodynamiques par minimisation de l’énergie de Gibbs (GEMS). Le modèle calibré permet de simuler des géométries voxellisées réalistes, à résolution submicronique, intégrant à la fois les phases principales (C-S-H, portlandite) et les hydrates mineurs, prêtes à être utilisées dans des simulations micromécaniques.
La deuxième contribution porte sur la reconstruction expérimentale de microstructures 3D étiquetées par phase à partir d’images µ-CT, à l’aide d’un nouveau protocole de segmentation supervisé par QEDS. Un processus de traitement d’image hybride a été développé pour pallier aux limites connues liées au chevauchement des niveaux de gris dans les images µ-CT. Ce processus intègre un filtrage par appariement de blocs en 4D (BM4D) permettant un affinement et débruitage des contrastes, et une classification par apprentissage automatique entraînée sur des cartes QEDS alignées avec les volumes µ-CT. Ce processus de segmentation permet une identification fiable des phases critiques telles que la ferrite, la portlandite et les hydrates, même en cas de forte superposition de leurs signatures en niveaux de gris. La méthode a été appliquée avec succès à des microcubes pour essais mécaniques, produisant des volumes numériques à résolution de phase. La méthode a permis de quantifier leur hétérogénéité spatiale ainsi que leurs caractéristiques morphologiques.
La troisième contribution introduit un cadre statistique spatial pour la comparaison quantitative entre microstructures simulées et expérimentales. Des fonctions descriptrices, notamment la fonction de corrélation à deux points (S₂) et la fonction du chemin linéaire (L), ont été calculées pour des groupes de phases harmonisés issus des volumes µiC et µ-CT. Un volume représentatif (RVE) de 200 µm³ a été sélectionné sur la base de la stabilité des fractions de phase et de la convergence de la distribution granulométrique des particules. Les comparaisons fondées sur les descripteurs ont mis en évidence des différences morphologiques significatives, telles que des gradients plus lissés et une connectivité poreuse plus faible dans les microstructures simulées, soulignant ainsi la valeur des données expérimentales pour capturer le réalisme topologique. Ces analyses appuient la validation des modèles d’hydratation par descripteurs statistique de la microstructure et éclairent leur pertinence pour les simulations micromécaniques.
L’ensemble de ces contributions établit un cadre robuste et ancré expérimentalement pour la modélisation de la pâte cimentaire statistiquement validée, morphologiquement réaliste et adaptée aux études mécaniques multiéchelles. Cette recherche renforce le lien entre simulation numérique et réalité expérimentale, tout en ouvrant la voie à des outils de prédiction plus fiables dans la modélisation multiéchelle de matériaux cimentaires alternatifs
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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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