7 results on '"Cheikh Sleiman, Hani"'
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2. A flexible generative algorithm for growing in silico placentas.
- Author
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de Oliveira, Diana C., Cheikh Sleiman, Hani, Payette, Kelly, Hutter, Jana, Story, Lisa, Hajnal, Joseph V., Alexander, Daniel C., Shipley, Rebecca J., and Slator, Paddy J.
- Abstract
The placenta is crucial for a successful pregnancy, facilitating oxygen exchange and nutrient transport between mother and fetus. Complications like fetal growth restriction and pre-eclampsia are linked to placental vascular structure abnormalities, highlighting the need for early detection of placental health issues. Computational modelling offers insights into how vascular architecture correlates with flow and oxygenation in both healthy and dysfunctional placentas. These models use synthetic networks to represent the multiscale feto-placental vasculature, but current methods lack direct control over key morphological parameters like branching angles, essential for predicting placental dysfunction. We introduce a novel generative algorithm for creating in silico placentas, allowing user-controlled customisation of feto-placental vasculatures, both as individual components (placental shape, chorionic vessels, placentone) and as a complete structure. The algorithm is physiologically underpinned, following branching laws (i.e. Murray's Law), and is defined by four key morphometric statistics: vessel diameter, vessel length, branching angle and asymmetry. Our algorithm produces structures consistent with in vivo measurements and ex vivo observations. Our sensitivity analysis highlights how vessel length variations and branching angles play a pivotal role in defining the architecture of the placental vascular network. Moreover, our approach is stochastic in nature, yielding vascular structures with different topological metrics when imposing the same input settings. Unlike previous volume-filling algorithms, our approach allows direct control over key morphological parameters, generating vascular structures that closely resemble real vascular densities and allowing for the investigation of the impact of morphological parameters on placental function in upcoming studies. Author summary: The placenta is important in ensuring a healthy pregnancy by facilitating the exchange of oxygen and nutrients between the mother and the fetus. Disturbances of placental function are often associated with abnormalities in the placental vascular structure, and detecting these issues early on is crucial. To understand the connection between placental vascular architecture, blood flow, and oxygenation, computational models have been used. These use synthetic networks which lack precise control over crucial morphological parameters, such as branching angles, essential for predicting placental dysfunction. Our contribution is a new approach that allows for the creation of virtual placentas that closely resemble real vascular characteristics. It enables users to customize the feto-placental vascular architecture at various levels, including individual components like placental shape, chorionic vessels, and placentone, as well as the complete structure. The flexibility of this pipeline opens the door for investigating the direct impact of morphological parameters on placental function. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
3. From tomographic imaging to numerical simulations: an open-source workflow for true morphology mesoscale FE meshes
- Author
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Cheikh Sleiman, Hani, primary, Moreira, Murilo Henrique, additional, Tengattini, Alessandro, additional, and Dal Pont, Stefano, additional
- Published
- 2024
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4. Simultaneous x-ray and neutron 4D tomographic study of drying-driven hydro-mechanical behavior of cement-based materials at moderate temperatures
- Author
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Cheikh Sleiman, Hani, Tengattini, Alessandro, Briffaut, Matthieu, Huet, Bruno, and Dal Pont, Stefano
- Published
- 2021
- Full Text
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5. Insights into thermo-hydro-mechanical (THM) behavior of cementitious materials by means of simultaneous neutron/X-ray tomography and 3D mesoscopic modeling
- Author
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Cheikh Sleiman, Hani
- Abstract
In the last few decades, the significant advances in full-field techniques have allowed unprecedented insight into local processes. Notably, for cement-based materials, x-ray and neutron tomography lend themselves as highly complementary tools for the study of their THM behavior. In this communication, the analysis of the in-situ neutron tomography data-set has allowed for the quantification of the 4D moisture profiles thanks to a multiphase partitioning method applied at the voxel level. In addition, the analysis of the acquired simultaneous neutron/x-ray tomography of the cement paste sample (once aligned in time and across modalities) has allowed for the extraction of the extensive fracture network and for the estimate of its interplay with local drying. Finally, a CT-FE mapping scheme was proposed which consisted of extracting the mesoscale morphology of concrete (aggregates and pores) from x-ray/neutron attenuation fields and presenting it explicitly on a FE mesh. This has permitted to perform 3D multiphase THM simulation of concrete at the mesoscale., Academic Journal of Civil Engineering, Vol 39 No 1 (2021): Special Issue - RUGC 2021
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- 2021
- Full Text
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6. Apport de la tomographie Neutron/rayon X pour la modélisation du séchage des matériaux poreux cohésifs
- Author
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Cheikh Sleiman, Hani and STAR, ABES
- Subjects
Neutron tomography ,[CHIM.MATE] Chemical Sciences/Material chemistry ,Tomographie neutronique ,Tomographie rayon-X ,X-Ray tomograhy ,Béton ,Concrete ,Drying ,Séchage - Abstract
The drying of cement-based materials affects directly their durability, which has a major economic, societal, and environmental impact.The conventional experimental techniques such as gravimetric and sensor-based measurements, which are employed to study the drying-driven processes, provide only bulk-averaged or point-wise measurements which are not sufficient to characterize these processes. However, the significant advances in full-field techniques have allowed unprecedented insight into these local processes. Notably, for cement-based materials, x-ray and neutron tomography lend themselves as highly complementary tools for the study of their THM behavior. In fact, the high sensitivity to density variations of x-ray imaging gives access to the developments of fractures, in 4D (3D+time). On the other hand, neutron tomography allows the study of the evolution of the moisture field in 4D, thanks to its high hydrogen sensitivity.This Ph.D. takes advantage of these two highly complementary techniques, which, together with advanced numerical modeling tools, allowed for a novel experimental/numerical insight to study the drying-driven physical processes in cement-based materials.In this work, two experimental campaigns were performed at the NeXT instrument located at the ILL. In the first campaign, neutron tomography was employed to characterize the moisture distribution of a set of cylindrical mortar samples which were set to dry sequentially in a TH controlled environment (T = 20℃ et RH = 35%) to represent different hydric states. The main phases of the mortar (aggregates, cement paste, and voids were separated, and saturation profiles were deduced and validated against the weight loss measurements. In the second experimental campaign, more complexity was added to the experimental drying conditions by heating concrete and cement paste samples up to moderate temperature which has led to the appearance of cracks in the later sample. The analysis of the acquired simultaneous neutron/x-ray data-set (once aligned in time and across modalities) allowed for the quantification of the 4D moisture profiles which were found to predict an overall water loss at hydric equilibrium coherent with the corresponding analytical analysis. In the cement paste sample, the x-ray dataset captures the evolution of an extensive cracking network, opening, and propagation toward the core of the sample. Then, a novel analysis procedure was proposed which allowed the extraction of these fractures and the analysis of their interplay with local drying as captured through neutron imaging.On the other hand, the numerical approach employed in this study consisted of improving the numerical model predictive capacity by assessing the implications of common simplifications on the modeling response. These common simplifications can be divided in three main categories which regard the consideration of gaseous transport modes, the TH and HM couplings, and the morphological description of the material. Quantification of these simplifications effects regarding the used model and the choice of TH coupling laws was done by comparing mass loss response surfaces in relative humidity and temperature space for multiple configurations. The results show relative error maps at early, mid, and late drying stages for every compared case. On the other hand, the simplification regarding the HM coupling was evaluated in a 2D mesoscopic simulation framework where an artificial concrete mesostructure had to be generated for cracking localization purposes. The cracking impact was then assessed both locally on the saturation fields and on the global mass loss response. Finally, a CT-FE mapping scheme was proposed which consisted of extracting the mesoscale morphology of concrete (aggregates and pores) from x-ray/neutron attenuation fields and presenting it explicitly on a FE mesh. This has permitted to perform 3D multiphase THM simulation of concrete at the mesoscale., Le séchage des matériaux cimentaires affecte directement leur durabilité, ce qui a un impact économique, sociétal et environnemental majeur.Les techniques expérimentales conventionnelles, qui sont utilisées pour étudier les processus de séchage, ne fournissent que des mesures moyennées ou ponctuelles qui ne sont pas suffisantes pour caractériser ces processus intrinsèquement hétérogènes. Cependant, les progrès significatifs dans les techniques de plein champ ont permis une observation sans précédent de ces processus locaux. Notamment, la tomographie par rayons X et neutrons se prête comme des outils très complémentaires pour l'étude du comportement THM des matériaux cimentaires. En effet, la grande sensibilité aux variations de densité de l'imagerie par rayons X donne accès aux évolutions des fractures, en 4D (3D + temps). D'autre part, la tomographie neutronique permet d'étudier l'évolution du champ d'humidité en 4D, grâce à sa haute sensibilité à l'hydrogène.Ce travail a tiré profit de ces deux techniques très complémentaires, qui, associées à des outils de modélisation numérique avancés, ont permis une nouvelle vision expérimentale/numérique pour étudier les processus physiques induits par le séchage dans les matériaux cimentaires.Dans ce travail, deux campagnes expérimentales ont été réalisées sur l'instrument NeXT situé à l'ILL. Dans la première campagne, la tomographie neutronique a été utilisée pour caractériser la distribution d'humidité d'un ensemble d'échantillons de mortier cylindrique qui ont été mis à sécher séquentiellement dans un environnement TH contrôlé (T = 20℃ et RH = 35%) pour représenter différents états hydriques. Les principales phases du mortier (granulats, pâte de ciment et vides) ont été séparées, et des profils de saturation ont été déduits et validés par rapport aux mesures de perte de poids. Dans la deuxième campagne expérimentale, plus de complexité a été ajoutée aux conditions de séchage expérimentales en chauffant des échantillons de béton et de pâte de ciment à une température modérée, ce qui a conduit à l'apparition de fissures dans l'échantillon ultérieur. L'analyse de l'ensemble de données neutrons/rayons X simultanément acquis a permis de quantifier les profils d'humidité 4D. Dans l'échantillon de pâte de ciment, les données de la tomographie rayons X ont capturé l'évolution d'un vaste réseau de fissuration ainsi que leurs ouvertures et leur propagation vers le cœur de l'échantillon. Ensuite, une nouvelle procédure d'analyse a été proposée qui a permis l'extraction de ces fractures et l'analyse de leur interaction avec le séchage local tel que capturé par imagerie neutronique.D'autre part, l'approche numérique employée dans cette étude a consisté à évaluer les implications des simplifications courantes sur la réponse de modélisation. Ces simplifications communes peuvent être divisées en trois grandes catégories qui concernent la prise en compte des modes de transport gazeux, les couplages TH et HM et la description morphologique du matériau. La quantification de ces effets de simplification concernant le modèle utilisé et le choix des lois de couplage TH a été réalisée en comparant les surfaces de réponse de la perte de masse dans un espace d'humidité relative et de température pour plusieurs configurations. Les résultats montrent des cartes d'erreur relative aux stades de séchage précoce, intermédiaire et tardif pour chaque cas comparé. D'autre part, la simplification concernant le couplage HM a été évaluée dans un cadre de simulation mésoscopique 2D. L'impact de la fissuration a ensuite été évalué à la fois localement sur les champs de saturation et sur la réponse globale de la perte de masse. Enfin, un schéma CT-EF a été proposé qui a consisté à extraire la morphologie du béton (agrégats et pores) des images rayons X/neutrons et de la présenter explicitement sur un maillage EF. Cela a permis de réaliser des simulations THM multiphasique 3D du béton à l'échelle mésoscopique.
- Published
- 2021
7. Influence of common simplifications on the drying of cement-based materials up to moderate temperatures
- Author
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Cheikh Sleiman, Hani, primary, Briffaut, Matthieu, additional, Dal Pont, Stefano, additional, Tengattini, Alessandro, additional, and Huet, Bruno, additional
- Published
- 2020
- Full Text
- View/download PDF
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