111. Fourth-order phase field modelling of brittle fracture with strong form meshless methodIzaz Ali, Gašper Vuga, Boštjan Mavrič, Umut Hanoglu, Božidar Šarler, 2024, original scientific article Abstract: This study aims to find a solution for crack propagation in 2D brittle elastic material using the local radial basis function collocation method. The staggered solution of the fourth-order phase field and mechanical model is structured with polyharmonic spline shape functions augmented with polynomials. Two benchmark tests are carried out to assess the performance of the method. First, a non-cracked square plate problem is solved under tensile loading to validate the implementation by comparing the numerical and analytical solutions. The analysis shows that the iterative process converges even with a large loading step, whereas the non-iterative process requires smaller steps for convergence to the analytical solution. In the second case, a single-edge cracked square plate subjected to tensile loading is solved, and the results show a good agreement with the reference solution. The effects of the incremental loading, length scale parameter, and mesh convergence for regular and scattered nodes are demonstrated. This study presents a pioneering attempt to solve the phase field crack propagation using a strong-form meshless method. The results underline the essential role of the represented method for an accurate and efficient solution to crack propagation. It also provides valuable insights for future research towards more sophisticated material models.
Keywords: strong form meshless method, fourth-order phase field, crack propagation, staggered approach, polyharmonic splines
Published in DiRROS: 17.12.2024; Views: 42; Downloads: 28
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112. Direct reconstruction of wet foam from sparse-view, dynamic X-ray CT scansJens Renders, Lucia Mancini, Jan De Beenhouwer, Jan Sijbers, 2024, original scientific article Abstract: X-ray imaging of wet foam dynamics with a high temporal resolution (e.g., 3D videos with a 10 Hz frame rate) requires fast rotation of either the foam sample or the X-ray gantry. This, however, strongly limits the number of X-ray projections per rotation that can be acquired. As a result, conventional computed tomography reconstruction methods generate 3D images with severe undersampling artefacts, complicating subsequent foam analysis. Herein, BubSub, a novel tomographic reconstruction approach that reconstructs a 4D (3D plus time) dynamic image of wet foam bubbles from sparse-view X-ray projections by leveraging prior knowledge about the evolving foam structure, is introduced. BubSub adapts a collection of subdivision surfaces with spherical topology to represent liquid–gas interfaces of foam bubbles. Estimation of bubble positions and shapes at each time point is achieved by minimizing the projection distance in relation to the measured projections. BubSub operates efficiently with minimal memory usage, exhibits robustness against noise, and provides accurate reconstructions, even when the available projections are limited, as evidenced by various experiments using both simulated and real wet foam X-ray data.
Keywords: redki pogledi, dinamika pene, rentgenska mikrotomografija, tomografska rekonstrukcija, sparse views, foam dynamics, X-ray microtomography, tomographic reconstruction
Published in DiRROS: 16.12.2024; Views: 71; Downloads: 39
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113. A multifaceted approach to understanding protein-buffer interactions in biopharmaceuticalsBlaž Lebar, Maria Toplishek, Boštjan Japelj, Ernest Šprager, Rok Podlipec, Tilen Knaflič, Iztok Urbančič, Benjamin Knez, Mitja Zidar, Jure Cerar, Janez Mravljak, Aleš Žula, Denis Arčon, Janez Plavec, Stane Pajk, 2024, original scientific article Published in DiRROS: 16.12.2024; Views: 76; Downloads: 44
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114. Identifying crystal nucleation mechanisms in a synthetic trachybasalt: a multimodal approachStefano Peres, Thomas A. Griffiths, Fabio Colle, Stefano Iannini Lelarge, Matteo Masotta, Alessio Pontesilli, Lucia Mancini, Rainer Abart, 2024, original scientific article Abstract: To develop new criteria to distinguish different crystal nucleation mechanisms in silicate melts, we performed crystallization experiments using a synthetic hydrous (2 wt% H2O) trachybasalt and combined three-dimensional information from synchrotron X-ray computed microtomography with two-dimensional mapping of crystallographic orientation relationships (CORs) using electron backscatter diffraction. Crystallization experiments were performed at 400 MPa by cooling the melt from 1300 °C to resting temperatures of 1150 and 1100 °C and maintaining isothermal conditions for 30 min and 8 h. Three distinct titanomagnetite (Tmt) populations formed: (1) skeletal crystals, isolated or partially embedded in clinopyroxene (Cpx); (2) anhedral crystals, always attached to Cpx; (3) flattened needle-shaped crystals, embedded in Cpx. These morphologically different Tmt populations formed in response to one cooling event, with varying nucleation mechanisms and at different undercooling conditions. The clustered three-dimensional distribution of population 2 and 3 Tmt grains and the high proportion of Tmt-Cpx interfaces sharing CORs indicate that these Tmt grains heterogeneously nucleated on Cpx. The near-random three-dimensional distribution of (often isolated) population 1 Tmt grains, together with the low proportion of Tmt-Cpx interfaces sharing CORs, imply their isolated, possibly homogeneous nucleation, potentially followed by heterogeneous nucleation of Cpx on population 1 Tmt. Heterogeneous nucleation in slightly to moderately undercooled magmas should affect the sequence of crystallization as well as morphology and clustering of crystals, which may actively contribute to the variation of rheological parameters like viscosity. Finally, observed intra- and inter-sample variations in Tmt-Cpx COR frequencies indicate the potential for this parameter to record further petrological information.
Keywords: experimental petrology, nucleation mechanisms, X-ray microtomography, crystal clustering, heterogeneous nucleation
Published in DiRROS: 16.12.2024; Views: 73; Downloads: 59
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115. Effects of different China and ball clays on traditional ceramic process : a multi-methodological approachAndreas Bernasconi, Nicoletta Marinoni, Lucia Mancini, Marco Voltolini, Fernando Francescon, R. Sartori, Alessandro Pavese, 2024, original scientific article Abstract: A combination of technological properties, mineralogical composition and three-dimension (3D) imaging is proposed to get insights into sanitary-ware ceramic bodies of the Vitreous-China technology as a function of the different clay raw materials used in the formulation of slip. Particular attention is paid to the effects induced along the production chain, during casting, after drying (dried body) and after firing (fired body). The different combinations of China and ball clays lead to different casting behaviour, in first instance, and to different mechanical strength, then, due to variations in the particle size distribution rather than in the mineralogical composition. In particular, the finer the particle size, the finer the pore size and, in addition, the better the mechanical properties (with a maximum of 4.7 MPa), due to a better packing. However, fine particle size distribution worsens the slip’s behaviour into moulds, impacting negatively on productivity, with a 17 % reduction of casting thickness. Upon firing process, such differences are mitigated by the body densification and result in more similar pores’ distributions, though the importance of the mineralogical composition is revealed. In fact, differences in mineralogical phases’ contents and in kaolinite HI index guide the comprehension of high temperature phase evolution and technological properties like the fired body thermal expansion, foremost via residual quartz. These results are important for a plastic raw materials’s selection within the ceramic sanitary-ware process.
Keywords: clay raw materials, vitreous-China technology, synchrotron X-ray microtomography, X-ray diffraction, ceramic properties, phase analysis
Published in DiRROS: 16.12.2024; Views: 80; Downloads: 53
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116. ▫$Ni-MoO_2$▫ composite coatings electrodeposited at porous Ni substrate as efficient alkaline water splitting cathodesAleksandar M. Petričević, Jelena D. Gojgić, Christian I. Bernäcker, Thomas Rauscher, Marjan Bele, Milutin Smiljanić, Nejc Hodnik, Nevenka Elezović, Vladimir Jović, Mila N. Krstajić Pajić, 2024, original scientific article Published in DiRROS: 16.12.2024; Views: 78; Downloads: 37
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118. Strong-form meshless numerical modelling of visco-plastic materialGašper Vuga, Boštjan Mavrič, Božidar Šarler, 2024, original scientific article Abstract: This work extends our research on the strong-form meshless Radial Basis Function - Finite Difference (RBF-FD) method for solving non-linear visco-plastic mechanical problems. The polyharmonic splines with second-order polynomial augmentation are used for the shape functions. Their coefficients are determined by collocation. Three different approaches (direct, composed, and hybrid) are used for the numerical evaluation of the divergence operator in the equilibrium equation. They are presented and assessed for a visco-plastic material model with continuously differentiable material properties. It is shown that the direct approach is not suitable in this respect. In comparison to the previously investigated elasto-plasticity, it is shown that the composed approach can successfully cope with visco-plastic problems and is found to be even more accurate than the hybrid approach, which has previously proven to be most stable and effective in solving elasto-plasticity. This work extends the applicability of strong-form RBF-FD methods and opens up new areas of modelling non-linear solid mechanics.
Keywords: visco-plastic material responses, hybrid radial basis, generated finite differences, polyharmonic splines
Published in DiRROS: 16.12.2024; Views: 67; Downloads: 38
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119. Cytotoxicity assessment of HDPE microplastic on Tetrahymena thermophila (Protozoa, Ciliate) : assuring quality and FAIR dataValentina Perc, Veno Kononenko, Nina Jeliaskova, Matej Hočevar, Slavko Kralj, Darko Makovec, Maja Caf, Damjana Drobne, Sara Novak, 2024, original scientific article Keywords: cytotoxicity, microplastic, HDPE, FAIR data, tetrahymena thermophila
Published in DiRROS: 16.12.2024; Views: 68; Downloads: 38
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120. Preservation of 5-hydroxymethylcytosine levels in LRIG1 across genomic DNA and cell-free DNA in glioma patientsDaša Jevšinek Skok, Luka Bolha, Nina Hauptman, 2024, other scientific articles Abstract: Cell-free DNA (cfDNA) has recently emerged as a promising minimally invasive diagnostic biomarker for various cancers. In this study, our aim was to identify cfDNA biomarkers by investigating genes that displayed significant differences between glioma patients and their corresponding controls. To accomplish this, we utilized publicly available data from the Gene Expression Omnibus, focusing on 5-hydroxymethylcytosine (5hmC) profiles in both cfDNA and genomic DNA (gDNA) from glioma patients and healthy individuals. The intersection of gene lists derived from these comparative analyses unveiled LRIG1 and ZNF703 as the two genes with elevated 5hmC levels in both the cfDNA of glioma patients and gDNA of glioma tissue compared to their respective controls. The gene expression data revealed both genes were upregulated in glioma tissue compared to normal brain tissue. Integration of 5hmC data revealed a strong positive correlation in the glioma tissue group between 5hmC and the gene expression of the LRIG1 gene. Furthermore, exploration using the AmiCa web tool indicated that LRIG1 gene expression was elevated compared to 17 other cancers included in the database, emphasizing its potential as a distinctive biomarker across multiple cancer types.
Keywords: cell-free DNA, glioma, 5-hydroxymethylcytosine, biomarkers
Published in DiRROS: 13.12.2024; Views: 96; Downloads: 38
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