Articles de revues : « Multiscale deformations »

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Shahi, Shahrokh, et Soheil Mohammadi. « A Multiscale Finite Element Simulation of Human Aortic Heart Valve ». Applied Mechanics and Materials 367 (août 2013) : 275–79. http://dx.doi.org/10.4028/www.scientific.net/amm.367.275.

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Some of the heart valve diseases can be treated by surgical replacement with either a mechanical or bioprosthetic heart valve (BHV). Recently, tissue-engineered heart valves (TEHVs) have been proposed to be the ultimate solution for treating valvular heart disease. In order to improve the durability and design of artificial heart valves, recent studies have focused on quantifying the biomechanical interaction between the organ, tissue, and cellular –level components in native heart valves. Such data is considered fundamental to designing improved BHVs. Mechanical communication from the larger scales affects active biomechanical processes. For instance any organ-scale motion deforms the tissue, which in turn deforms the interstitial cells (ICs). Therefore, a multiscale solution is required to study the behavior of human aortic valve and to predict local cell deformations. The proposed multiscale finite element approach takes into account large deformations and nonlinear anisotropic hyperelastic material models. In this simulation, the organ scale motion is computed, from which the tissue scale deformation will be extracted. Similarly, the tissue deformation will be transformed into the cell scale. Finally, each simulation is verified against a number of experimental measures.

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LI, ZHIPING. « MULTISCALE MODELLING AND COMPUTATION OF MICROSTRUCTURES IN MULTI-WELL PROBLEMS ». Mathematical Models and Methods in Applied Sciences 14, n^o 09 (septembre 2004) : 1343–60. http://dx.doi.org/10.1142/s0218202504003647.

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A multiscale model and numerical method for computing microstructures with large and inhomogeneous deformation is established, in which the microscopic and macroscopic information is recovered by coupling the finite order rank-one convex envelope and the finite element method. The method is capable of computing microstructures which are locally finite order laminates. Numerical experiments on a double-well problem show that plenty of stress free large deformations can be achieved by microstructures consisting of piecewise simple twin laminates.

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Brozzetti, Francesco, Alessandro Cesare Mondini, Cristina Pauselli, Paolo Mancinelli, Daniele Cirillo, Fausto Guzzetti et Giusy Lavecchia. « Mainshock Anticipated by Intra-Sequence Ground Deformations : Insights from Multiscale Field and SAR Interferometric Measurements ». Geosciences 10, n^o 5 (15 mai 2020) : 186. http://dx.doi.org/10.3390/geosciences10050186.

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The 2016 Central Italy seismic sequence was characterized by two main events: 24 August, Mw 6, and 30 October, Mw 6.5. We carried out high-resolution field sampling and DInSAR analysis of the coseismic and intra-sequence ground deformations along the Mt Vettore-Mt Bove causative fault (VBF). We found that during the intra-sequence period (24 August–30 October), the ground experienced some deformations whose final patterns seemed to be retraced and amplified by the following mainshock. We interpreted that (i) immediately after the 24 August earthquake, the deformation observed in the southern VBF expanded northwards and westwards over a Length of Deforming Ground (LDG) ranging between 28.7 and 36.3 km, and (ii) it extended to the whole portion of the hanging wall that was later affected by mainshock coseismic deformation. Assuming the LDG to be an indicator for an expected (=coseismic) surface rupture length and using known scaling functions, we obtained 6.4 ≤ Mw ≤ 6.7 for a possible incoming earthquake, which is consistent with the mainshock magnitude. We suggest that the evolution of the ground deformations after a significant seismic event might provide insights on the occurrence of new earthquakes with magnitudes comparable to or larger than the former.

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Efendiev, Yalchin, Juan Galvis et M. Sebastian Pauletti. « Multiscale Finite Element Methods for Flows on Rough Surfaces ». Communications in Computational Physics 14, n^o 4 (octobre 2013) : 979–1000. http://dx.doi.org/10.4208/cicp.170512.310113a.

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AbstractIn this paper, we present the Multiscale Finite Element Method (MsFEM) for problems on rough heterogeneous surfaces. We consider the diffusion equation on oscillatory surfaces. Our objective is to represent small-scale features of the solution via multiscale basis functions described on a coarse grid. This problem arises in many applications where processes occur on surfaces or thin layers. We present a unified multiscale finite element framework that entails the use of transformations that map the reference surface to the deformed surface. The main ingredients of MsFEM are (1) the construction of multiscale basis functions and (2) a global coupling of these basis functions. For the construction of multiscale basis functions, our approach uses the transformation of the reference surface to a deformed surface. On the deformed surface, multiscale basis functions are defined where reduced (1D) problems are solved along the edges of coarse-grid blocks to calculate nodal multiscale basis functions. Furthermore, these basis functions are transformed back to the reference configuration. We discuss the use of appropriate transformation operators that improve the accuracy of the method. The method has an optimal convergence if the transformed surface is smooth and the image of the coarse partition in the reference configuration forms a quasiuniform partition. In this paper, we consider such transformations based on harmonic coordinates (following H. Owhadi and L. Zhang [Comm. Pure and Applied Math., LX(2007), pp. 675-723]) and discuss gridding issues in the reference configuration. Numerical results are presented where we compare the MsFEM when two types of deformations are used for multiscale basis construction. The first deformation employs local information and the second deformation employs a global information. Our numerical results show that one can improve the accuracy of the simulations when a global information is used.

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Zewail, Rami, et Ahmed Hag-ElSafi. « MULTISCALE SPARSE APPEARANCE MODELING AND SIMULATION OF PATHOLOGICAL DEFORMATIONS ». ICTACT Journal on Image and Video Processing 8, n^o 1 (1 août 2017) : 1596–605. http://dx.doi.org/10.21917/ijivp.2017.0225.

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Grondin, F., M. Bouasker, P. Mounanga, A. Khelidj et A. Perronnet. « Physico-chemical deformations of solidifying cementitious systems : multiscale modelling ». Materials and Structures 43, n^o 1-2 (5 février 2009) : 151–65. http://dx.doi.org/10.1617/s11527-009-9477-z.

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Bakhaty, Ahmed A., Sanjay Govindjee et Mohammad R. K. Mofrad. « A Coupled Multiscale Approach to Modeling Aortic Valve Mechanics in Health and Disease ». Applied Sciences 11, n^o 18 (8 septembre 2021) : 8332. http://dx.doi.org/10.3390/app11188332.

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Mechano-biological processes in the aortic valve span multiple length scales ranging from the molecular and cell to tissue and organ levels. The valvular interstitial cells residing within the valve cusps sense and actively respond to leaflet tissue deformations caused by the valve opening and closing during the cardiac cycle. Abnormalities in these biomechanical processes are believed to impact the matrix-maintenance function of the valvular interstitial cells, thereby initiating valvular disease processes such as calcific aortic stenosis. Understanding the mechanical behavior of valvular interstitial cells in maintaining tissue homeostasis in response to leaflet tissue deformation is therefore key to understanding the function of the aortic valve in health and disease. In this study, we applied a multiscale computational homogenization technique (also known as “FE2”) to aortic valve leaflet tissue to study the three-dimensional mechanical behavior of the valvular interstitial cells in response to organ-scale mechanical loading. We further considered calcific aortic stenosis with the aim of understanding the likely relationship between the valvular interstitial cell deformations and calcification. We find that the presence of calcified nodules leads to an increased strain profile that drives further growth of calcification.

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Karmarkar, Aditya P., Xiaopeng Xu et Karim El-Sayed. « Temperature and Process Dependent Material Characterization and Multiscale Stress Evolution Analysis for Performance and Reliability Management under Chip Package Interaction ». International Symposium on Microelectronics 2017, n^o 1 (1 octobre 2017) : 000013–24. http://dx.doi.org/10.4071/isom-2017-tp13_051.

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Abstract Distinct temperature and process dependent deformation behaviors under packaging temperature cycles are characterized for various packaging materials. Substrate and underfill deformations are described using Maxwell viscoelasticity model. Solder bump deformation is represented by incremental plasticity model. Anisotropic deformation in silicon and orthotropic deformation in substrate are also considered. The material deformation effects on stress evolutions during fabrication and under chip package interaction (CPI) are analyzed for a large package structure. Complex geometries spread over a large range of length scales are simulated using multi-level and multiscale sequential submodeling technique. Global package simulations show that substrate orthotropy has a significant impact on the package warpage during the assembly process. Sequential package assembly simulations are performed to examine the residual stresses at package, bump and interconnect scales. The results show that the package material behaviors during the assembly process affect not only the residual stresses in the large package structure but also in the local bump regions and the interconnect structures. The temperature dependent material non-linear behaviors under operating conditions also affect residual stresses and carrier mobility. This work demonstrates that developing performance and reliability management strategies under CPI should consider temperature and process dependent material deformations during fabrication and packaging.

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Zhou, Tingtao, Katerina Ioannidou, Franz-Josef Ulm, Martin Z. Bazant et R. J. M. Pellenq. « Multiscale poromechanics of wet cement paste ». Proceedings of the National Academy of Sciences 116, n^o 22 (9 mai 2019) : 10652–57. http://dx.doi.org/10.1073/pnas.1901160116.

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Capillary effects, such as imbibition drying cycles, impact the mechanics of granular systems over time. A multiscale poromechanics framework was applied to cement paste, which is the most common building material, experiencing broad humidity variations over the lifetime of infrastructure. First, the liquid density distribution at intermediate to high relative humidity is obtained using a lattice gas density functional method together with a realistic nanogranular model of cement hydrates. The calculated adsorption/desorption isotherms and pore size distributions are discussed and compare well with nitrogen and water experiments. The standard method for pore size distribution determination from desorption data is evaluated. Second, the integration of the Korteweg liquid stress field around each cement hydrate particle provided the capillary forces at the nanoscale. The cement mesoscale structure was relaxed under the action of the capillary forces. Local irreversible deformations of the cement nanograins assembly were identified due to liquid–solid interactions. The spatial correlations of the nonaffine displacements extend to a few tens of nanometers. Third, the Love–Weber method provided the homogenized liquid stress at the micrometer scale. The homogenization length coincided with the spatial correlation length of nonaffine displacements. Our results on the solid response to capillary stress field suggest that the micrometer-scale texture is not affected by mild drying, while nanoscale irreversible deformations still occur. These results pave the way for understanding capillary phenomena-induced stresses in heterogeneous porous media ranging from construction materials to hydrogels and living systems.

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Sotiropoulos, Gerasimos, et Vissarion Papadopoulos. « Nonlinear multiscale modeling of thin composite shells at finite deformations ». Computer Methods in Applied Mechanics and Engineering 391 (mars 2022) : 114572. http://dx.doi.org/10.1016/j.cma.2022.114572.

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Matous, Karel, et Antoinette M. Maniatty. « Multiscale modeling of elasto-viscoplastic polycrystals subjected to finite deformations ». Interaction and multiscale mechanics 2, n^o 4 (25 décembre 2009) : 375–96. http://dx.doi.org/10.12989/imm.2009.2.4.375.

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Falk, Korbinian, Ronny Lang et Michael Kaliske. « Multiscale Simulation to Determine Rubber Friction on Asphalt Surfaces ». Tire Science and Technology 44, n^o 4 (1 octobre 2016) : 226–47. http://dx.doi.org/10.2346/tire.16.440401.

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ABSTRACT The interaction between rubber and asphalt pavement depends on the roughness characteristics of the road surface, as well as the contact pressure, slip velocity, and temperature. A homogenization procedure of rubber friction, based on the finite element method, is presented, in order to gain surface dependent friction properties by numerical simulation. Furthermore, the method allows a deep insight into microscale phenomena, like real contact area, microscopic contact pressure, or flash temperature. Rubber undergoes large deformations in contact with rough surfaces. Therefore, the material characteristics of rubber need to be modeled by hyperelasticity and viscoelasticity at finite deformations and dependent on temperature. Thus, hysteresis friction, originating in energy dissipation of the bulk material, i.e., the viscoelastic properties, is evaluated. Adhesion friction is a phenomenon associated with the real contact area and is included in the proposed methodology by a physically motivated, fracture mechanical approach. The resulting macroscopic friction features are validated by experiments based on a linear friction tester. Analytical state of the art solutions are compared with the numerical results.

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TAKASAKI, KANEHISA, et TOSHIO NAKATSU. « ISOMONODROMIC DEFORMATIONS AND SUPERSYMMETRIC GAUGE THEORIES ». International Journal of Modern Physics A 11, n^o 31 (20 décembre 1996) : 5505–18. http://dx.doi.org/10.1142/s0217751x96002522.

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Seiberg-Witten solutions of four-dimensional supersymmetric gauge theories possess rich but involved integrable structures. The goal of this paper is to show that an isomonodromy problem provides a unified framework for understanding those various features of integrability. The Seiberg-Witten solution itself can be interpreted as a WKB limit of this isomonodromy problem. The origin of underlying Whitham dynamics (adiabatic deformation of an isospectral problem) too can be similarly explained by a more refined asymptotic method (multiscale analysis). The case of N = 2 SU (s) supersymmetric Yang-Mills theory without matter is considered in detail for illustration. The isomonodromy problem in this case is closely related to the third Painlevé equation and its multicomponent analogs. An implicit relation to [Formula: see text] fusion of topological sigma models is thereby expected.

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Ammosov, Dmitry, et Maria Vasilyeva. « Online Multiscale Finite Element Simulation of Thermo-Mechanical Model with Phase Change ». Computation 11, n^o 4 (29 mars 2023) : 71. http://dx.doi.org/10.3390/computation11040071.

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This paper presents a thermo-mechanical model with phase transition considering changes in the mechanical properties of the medium. The proposed thermo-mechanical model is described by a system of partial differential equations for temperature and displacements. In the model, soil deformations occur due to porosity growth caused by ice and water density differences. A finite-element approximation of this model on a fine grid is presented. The linearization from the previous time step is used to handle the nonlinearity of the problem. For reducing the size of the discrete problem, offline and online multiscale approaches based on the Generalized Multiscale Finite Element Method (GMsFEM) are proposed. A two-dimensional model problem simulating the heaving process of heterogeneous soil with a stiff inclusion was considered for testing the mathematical model and the multiscale approaches. Numerical solutions depict the process of soil heaving caused by changes in porosity due to the phase transition. The movement of the phase transition interface was observed. The change of medium properties, including the elastic modulus, was traced and corresponds to the phase transition interface. The proposed multiscale approaches significantly reduce the size of the discrete problem while maintaining reasonable accuracy. However, the online multiscale approach achieves better accuracy than the offline approach with fewer degrees of freedom.

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Pardoen, Benoît, Frédéric Collin, Pierre Bésuelle, Robert Charlier, Jean Talandier, Stefano Dal Pont, Philippe Cosenza, Abraham P. van den Eijnden et Jacques Desrues. « Modelling the multiscale behaviour of claystone : deformation, rupture, and hydro-mechanical phenomena around underground galleries ». E3S Web of Conferences 205 (2020) : 10003. http://dx.doi.org/10.1051/e3sconf/202020510003.

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In the context of underground exploitation, the behaviour of rocks near galleries and tunnels conditions their stability. Underground drilling generates deformations, damage, fracturing, and significant modification of flow characteristics in the surrounding rock. However, the influence of small-scale characteristics and behaviour on the rock deformations and damage at engineering scale remains a complex issue. Consequently, the multiscale behaviour of a clay rock is modelled starting from the large scale of the excavation damaged zone around galleries and then enriching the approach by considering microstructural characteristics from the scale of mineral inclusions. Lastly, a double-scale numerical framework is considered. It allows to relate small- to large-scale rock behaviour in terms of deformations and material rupture. In fact, the development of damage and cracking at microscale allows to predict large-scale fracturing. The developed method focuses on a claystone in the particular context of long-term management of high-level nuclear wastes by deep geological repository. The results highlight the possibilities of double-scale computing in the prediction of the behaviour of underground engineering structures.

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Mohanan, Vaisakh Vilavinalthundil, Ho Yi Lydia Mak, Nishan Gurung et Qin Xu. « Multiscale Soft Surface Instabilities for Adhesion Enhancement ». Materials 15, n^o 3 (23 janvier 2022) : 852. http://dx.doi.org/10.3390/ma15030852.

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Soft polymeric gels are susceptible to buckling-induced instabilities due to their great compliance to surface deformations. The instability patterns at soft interfaces have great potential in engineering functional materials with unique surface properties. In this work, we systematically investigated how swelling-induced instability patterns effectively improved the adhesive properties of soft polydimethylsiloxane (PDMS) gels. We directly imaged the formations of the surface instability features during the relaxation process of a swollen gel substrate. The features were found to greatly increase the adhesion energy of soft gels across multiple length scales, and the adhesion enhancement was associated with the variations of contact lines both inside the contact region and along the contact periphery. We expect that these studies of instability patterns due to swelling will further benefit the design of functional interfaces in various engineering applications.

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Zarei, Vahhab, Sijia Zhang, Beth A. Winkelstein et Victor H. Barocas. « Tissue loading and microstructure regulate the deformation of embedded nerve fibres : predictions from single-scale and multiscale simulations ». Journal of The Royal Society Interface 14, n^o 135 (octobre 2017) : 20170326. http://dx.doi.org/10.1098/rsif.2017.0326.

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Excessive deformation of nerve fibres (axons) in the spinal facet capsular ligaments (FCLs) can be a cause of pain. The axons are embedded in the fibrous extracellular matrix (ECM) of FCLs, so understanding how local fibre organization and micromechanics modulate their mechanical behaviour is essential. We constructed a computational discrete-fibre model of an axon embedded in a collagen fibre network attached to the axon by distinct fibre–axon connections. This model was used to relate the axonal deformation to the fibre alignment and collagen volume concentration of the surrounding network during transverse, axial and shear deformations. Our results showed that fibre alignment affects axonal deformation only during transverse and axial loading, but higher collagen volume concentration results in larger overall axonal strains for all loading cases. Furthermore, axial loading leads to the largest stretch of axonal microtubules and induces the largest forces on axon's surface in most cases. Comparison between this model and a multiscale continuum model for a representative case showed that although both models predicted similar averaged axonal strains, strain was more heterogeneous in the discrete-fibre model.

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Matouš, Karel, et Philippe H. Geubelle. « Multiscale modelling of particle debonding in reinforced elastomers subjected to finite deformations ». International Journal for Numerical Methods in Engineering 65, n^o 2 (2005) : 190–223. http://dx.doi.org/10.1002/nme.1446.

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Duque, Julia, Alessandra Bonfanti, Jonathan Fouchard, Lucia Baldauf, Sara R. Azenha, Emma Ferber, Andrew Harris, Elias H. Barriga, Alexandre J. Kabla et Guillaume Charras. « Rupture strength of living cell monolayers ». Nature Materials 23, n^o 11 (28 octobre 2024) : 1563–74. http://dx.doi.org/10.1038/s41563-024-02027-3.

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AbstractTo fulfil their function, epithelial tissues need to sustain mechanical stresses and avoid rupture. Although rupture is usually undesired, it is central to some developmental processes, for example, blastocoel formation. Nonetheless, little is known about tissue rupture because it is a multiscale phenomenon that necessitates comprehension of the interplay between mechanical forces and biological processes at the molecular and cellular scales. Here we characterize rupture in epithelial monolayers using mechanical measurements, live imaging and computational modelling. We show that despite consisting of only a single layer of cells, monolayers can withstand surprisingly large deformations, often accommodating several-fold increases in their length before rupture. At large deformation, epithelia increase their stiffness multiple fold in a process controlled by a supracellular network of keratin filaments. Perturbing the keratin network organization fragilized the monolayers and prevented strain-stiffening. Although the kinetics of adhesive bond rupture ultimately control tissue strength, tissue rheology and the history of deformation set the strain and stress at the onset of fracture.

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Grün, Jeremias, Marco Gohs et Frank Bauer. « Multiscale Structural Mechanics of Rotary Shaft Seals : Numerical Studies and Visual Experiments ». Lubricants 11, n^o 6 (23 mai 2023) : 234. http://dx.doi.org/10.3390/lubricants11060234.

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Although rotary shaft seals have been used successfully in many industrial applications for decades, their tribological behavior is still not completely understood. In-depth knowledge of the structural mechanics is essential for the design and optimization of such sealing systems. High complexity results from the multiscale interactions in the tribological system rotary shaft seal. Large macroscopic deformations occur due to the hyperelastic material behavior of elastomers coupled with microscopic tangential distortions of the sealing edge surface in the contact area. This paper includes both numerical and experimental studies on the tribological behavior of rotary shaft seals. A multiscale finite element model provides the simulation of the macroscopic deformations and the microscopic displacements. A test rig equipped with a hollow glass shaft enables in situ visual contact analyses, qualitative determinations of pressure distributions and quantitative measurements of elastomer surface distortions. The optical phenomenon of frustrated total internal reflection enables qualitative evaluations of the pressure distribution. Particle image velocimetry (PIV) is employed to quantify the tangential distortions. The test rig enables the measurement of the friction torque with the same configuration. The results of the numerical and experimental investigations for the radial load, friction torque and tangential distortions are compared and discussed. This serves to validate the simulation methods and the correlation of the measured parameters. This finally results in a solid and validated basis for further tribological investigations of rotary shaft seals.

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Arora, Hari, Ria Mitchell, Richard Johnston, Marinos Manolesos, David Howells, Joseph Sherwood, Andrew Bodey et Kaz Wanelik. « Correlating Local Volumetric Tissue Strains with Global Lung Mechanics Measurements ». Materials 14, n^o 2 (18 janvier 2021) : 439. http://dx.doi.org/10.3390/ma14020439.

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The mechanics of breathing is a fascinating and vital process. The lung has complexities and subtle heterogeneities in structure across length scales that influence mechanics and function. This study establishes an experimental pipeline for capturing alveolar deformations during a respiratory cycle using synchrotron radiation micro-computed tomography (SR-micro-CT). Rodent lungs were mechanically ventilated and imaged at various time points during the respiratory cycle. Pressure-Volume (P-V) characteristics were recorded to capture any changes in overall lung mechanical behaviour during the experiment. A sequence of tomograms was collected from the lungs within the intact thoracic cavity. Digital volume correlation (DVC) was used to compute the three-dimensional strain field at the alveolar level from the time sequence of reconstructed tomograms. Regional differences in ventilation were highlighted during the respiratory cycle, relating the local strains within the lung tissue to the global ventilation measurements. Strains locally reached approximately 150% compared to the averaged regional deformations of approximately 80–100%. Redistribution of air within the lungs was observed during cycling. Regions which were relatively poorly ventilated (low deformations compared to its neighbouring region) were deforming more uniformly at later stages of the experiment (consistent with its neighbouring region). Such heterogenous phenomena are common in everyday breathing. In pathological lungs, some of these non-uniformities in deformation behaviour can become exaggerated, leading to poor function or further damage. The technique presented can help characterize the multiscale biomechanical nature of a given pathology to improve patient management strategies, considering both the local and global lung mechanics.

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Glazoff, Michael V., Sergey N. Rashkeev, Yuri P. Pyt’ev, Jeong-Whan Yoon et Simon Sheu. « Interplay between plastic deformations and optical properties of metal surfaces : A multiscale study ». Applied Physics Letters 95, n^o 8 (24 août 2009) : 084106. http://dx.doi.org/10.1063/1.3213391.

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El Halabi, F., D. González, J. A. Sanz-Herrera et M. Doblaré. « A PGD-based multiscale formulation for non-linear solid mechanics under small deformations ». Computer Methods in Applied Mechanics and Engineering 305 (juin 2016) : 806–26. http://dx.doi.org/10.1016/j.cma.2016.03.039.

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Owen, David R., et Roberto Paroni. « Optimal Flux Densities for Linear Mappings and the Multiscale Geometry of Structured Deformations ». Archive for Rational Mechanics and Analysis 218, n^o 3 (21 mai 2015) : 1633–52. http://dx.doi.org/10.1007/s00205-015-0890-x.

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FREEDEN, W., et V. MICHEL. « WAVELET DEFORMATION ANALYSIS FOR SPHERICAL BODIES ». International Journal of Wavelets, Multiresolution and Information Processing 03, n^o 04 (décembre 2005) : 523–58. http://dx.doi.org/10.1142/s0219691305001007.

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In this paper, we introduce a multiscale technique for the analysis of deformation phenomena of the Earth. Classically, the basis functions under use are globally defined and show polynomial character. In consequence, only a global analysis of deformations is possible such that, for example, the water load of an artificial reservoir is hardly to model in that way. Up till now, the alternative to realize a local analysis can only be established by assuming the investigated region to be flat. In what follows, we propose a local analysis based on tools (Navier scaling functions and wavelets) taking the (spherical) surface of the Earth into account. Our approach, in particular, enables us to perform a zooming-in procedure. In fact, the concept of Navier wavelets is formulated in such a way that subregions with larger or smaller data density can accordingly be modelled with a higher or lower resolution of the model, respectively.

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Matano, Fabio, Mauro Caccavale, Giuseppe Esposito, Alberto Fortelli, Germana Scepi, Maria Spano et Marco Sacchi. « Integrated dataset of deformation measurements in fractured volcanic tuff and meteorological data (Coroglio coastal cliff, Naples, Italy) ». Earth System Science Data 12, n^o 1 (13 février 2020) : 321–44. http://dx.doi.org/10.5194/essd-12-321-2020.

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Abstract. Along the coastline of the Phlegraean Fields volcanic district, near Naples (Italy), severe retreat processes affect a large part of the coastal cliffs, mainly made of fractured volcanic tuff and pyroclastic deposits. Progressive fracturing and deformation of rocks can lead to hazardous sudden slope failures on coastal cliffs. Among the triggering mechanisms, the most relevant are related to meteorological factors, such as precipitation and thermal expansion due to solar heating of rock surfaces. In this paper, we present a database of measurement time series taken over a period of ∼4 years (December 2014–October 2018) for the deformations of selected tuff blocks in the Coroglio coastal cliff. The monitoring system is implemented on five unstable tuff blocks and is formed by nine crackmeters and two tiltmeters equipped with internal thermometers. The system is coupled with a total weather station, measuring rain, temperature, wind and atmospheric pressure and operating from January 2014 up to December 2018. Measurement frequencies of 10 and 30 min have been set for meteorological and deformation sensors respectively. The aim of the measurements is to assess the magnitude and temporal pattern of rock block deformations (fracture opening and block movements) before block failure and their correlation with selected meteorological parameters. The results of a multivariate statistical analysis of the measured time series suggest a close correlation between temperature and deformation trends. The recognized cyclic, sinusoidal changes in the width (opening–closing) of fractures and tuff block rotations are ostensibly linked to multiscale (i.e., daily, seasonal and annual) temperature variations. Some trends of cumulative multi-temporal changes have also been recognized. The full databases are freely available online at: https://doi.org/10.1594/PANGAEA.896000 (Matano et al., 2018) and https://doi.org/10.1594/PANGAEA.899562 (Fortelli et al., 2019).

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Kong, Ki-jeong. « Multiscale Simulation on the Electronic Structure Variation of the Carbon Nanotubes by Mechanical Deformations ». Journal of the Korean Physical Society 55, n^o 5(2) (14 novembre 2009) : 2218–23. http://dx.doi.org/10.3938/jkps.55.2218.

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Mäkipere, Krista, et Piroz Zamankhan. « Simulation of Fiber Suspensions—A Multiscale Approach ». Journal of Fluids Engineering 129, n^o 4 (18 août 2006) : 446–56. http://dx.doi.org/10.1115/1.2567952.

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The present effort is the development of a multiscale modeling, simulation methodology for investigating complex phenomena arising from flowing fiber suspensions. The present approach is capable of coupling behaviors from the Kolmogorov turbulence scale through the full-scale system in which a fiber suspension is flowing. Here the key aspect is adaptive hierarchical modeling. Numerical results are presented for which focus is on fiber floc formation and destruction by hydrodynamic forces in turbulent flows. Specific consideration was given to dynamic simulations of viscoelastic fibers in which the fluid flow is predicted by a method that is a hybrid between direct numerical simulations and large eddy simulation techniques and fluid fibrous structure interactions will be taken into account. Dynamics of simple fiber networks in a shearing flow of water in a channel flow illustrate that the shear-induced bending of the fiber network is enhanced near the walls. Fiber-fiber interaction in straight ducts is also investigated and results show that deformations would be expected during the collision when the surfaces of flocs will be at contact. Smaller velocity magnitudes of the separated fibers compare to the velocity before collision implies the occurrence of an inelastic collision. In addition because of separation of vortices, interference flows around two flocs become very complicated. The results obtained may elucidate the physics behind the breakup of a fiber floc, opening the possibility for developing a meaningful numerical model of the fiber flow at the continuum level where an Eulerian multiphase flow model can be developed for industrial use.

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Bakhoum, Ezzat G., et Cristian Toma. « Dynamical Aspects of Macroscopic and Quantum Transitions due to Coherence Function and Time Series Events ». Mathematical Problems in Engineering 2010 (2010) : 1–13. http://dx.doi.org/10.1155/2010/428903.

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This study presents the application of dynamical equations able to generate alternating deformations with increasing amplitude and delayed pulses in a certain material medium. It is considered that an external force acts at certain time interval (similar to a time series) upon the material medium in the same area. Using a specific differential equation (considering nonzero initial values and using a function similar to the coherence function between the external force and the deformations inside the material), it results that modulated amplitude oscillations appear inside the material. If the order of the differential dynamical equation is higher, supplementary aspects as different delayed pulses and multiscale behaviour can be noticed. These features are similar to non-Markov aspects of quantum transitions, and for this reason the mathematical model is suitable for describing both quantum phenomena and macroscopic aspects generated by sequence of pulses. An example of a quantum system, namely, the Hydrogen atom, is discussed.

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Yang, Yi, Yi Yang, Shubo Zhou, Yongbin Gao, Yadong Zhu, Xuefen Wan, Weiyu Hu et Xueqin Jiang. « MST : Multiscale Flow-Based Student–Teacher Network for Unsupervised Anomaly Detection ». Electronics 13, n^o 16 (14 août 2024) : 3224. http://dx.doi.org/10.3390/electronics13163224.

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Student–teacher networks have shown promise in unsupervised anomaly detection; however, issues such as semantic confusion and abnormal deformations still restrict the detection accuracy. To address these issues, we propose a novel student–teacher network named MST by integrating the multistage pixel-reserving bridge (MPRB) and the spatial compression autoencoder (SCA) to the MMR network. The MPRB enhances inter-level information interaction and local feature extraction, improving the anomaly localization and reducing the false detection area. The SCA bolsters global feature extraction, making the detection boundaries of larger defects clearer. By testing our network across various datasets, our method achieves state-of-the-art (SOTA) performance on AeBAD-S, AeBAD-V, and MPDD datasets, with image-level AUROC scores of 87.5%, 78.5%, and 96.5%, respectively. Furthermore, our method also exhibits competitive performance on the widely utilized MVTec AD dataset.

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Mordhorst, Mylena, Thomas Heidlauf et Oliver Röhrle. « Predicting electromyographic signals under realistic conditions using a multiscale chemo–electro–mechanical finite element model ». Interface Focus 5, n^o 2 (6 avril 2015) : 20140076. http://dx.doi.org/10.1098/rsfs.2014.0076.

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This paper presents a novel multiscale finite element-based framework for modelling electromyographic (EMG) signals. The framework combines (i) a biophysical description of the excitation–contraction coupling at the half-sarcomere level, (ii) a model of the action potential (AP) propagation along muscle fibres, (iii) a continuum-mechanical formulation of force generation and deformation of the muscle, and (iv) a model for predicting the intramuscular and surface EMG. Owing to the biophysical description of the half-sarcomere, the model inherently accounts for physiological properties of skeletal muscle. To demonstrate this, the influence of membrane fatigue on the EMG signal during sustained contractions is investigated. During a stimulation period of 500 ms at 100 Hz, the predicted EMG amplitude decreases by 40% and the AP propagation velocity decreases by 15%. Further, the model can take into account contraction-induced deformations of the muscle. This is demonstrated by simulating fixed-length contractions of an idealized geometry and a model of the human tibialis anterior muscle (TA). The model of the TA furthermore demonstrates that the proposed finite element model is capable of simulating realistic geometries, complex fibre architectures, and can include different types of heterogeneities. In addition, the TA model accounts for a distributed innervation zone, different fibre types and appeals to motor unit discharge times that are based on a biophysical description of the α motor neurons.

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Cohen, Noy, Andreas Menzel et Gal deBotton. « Towards a physics-based multiscale modelling of the electro-mechanical coupling in electro-active polymers ». Proceedings of the Royal Society A : Mathematical, Physical and Engineering Sciences 472, n^o 2186 (février 2016) : 20150462. http://dx.doi.org/10.1098/rspa.2015.0462.

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Owing to the increasing number of industrial applications of electro-active polymers (EAPs), there is a growing need for electromechanical models which accurately capture their behaviour. To this end, we compare the predicted behaviour of EAPs undergoing homogeneous deformations according to three electromechanical models. The first model is a phenomenological continuum-based model composed of the mechanical Gent model and a linear relationship between the electric field and the polarization. The electrical and the mechanical responses according to the second model are based on the physical structure of the polymer chain network. The third model incorporates a neo-Hookean mechanical response and a physically motivated microstructurally based long-chains model for the electrical behaviour. In the microstructural-motivated models, the integration from the microscopic to the macroscopic levels is accomplished by the micro-sphere technique. Four types of homogeneous boundary conditions are considered and the behaviours determined according to the three models are compared. For the microstructurally motivated models, these analyses are performed and compared with the widely used phenomenological model for the first time. Some of the aspects revealed in this investigation, such as the dependence of the intensity of the polarization field on the deformation, highlight the need for an in-depth investigation of the relationships between the structure and the behaviours of the EAPs at the microscopic level and their overall macroscopic response.

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Zarei, Vahhab, Rohit Y. Dhume, Arin M. Ellingson et Victor H. Barocas. « Multiscale modelling of the human lumbar facet capsular ligament : analysing spinal motion from the joint to the neurons ». Journal of The Royal Society Interface 15, n^o 148 (novembre 2018) : 20180550. http://dx.doi.org/10.1098/rsif.2018.0550.

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Due to its high level of innervation, the lumbar facet capsular ligament (FCL) is suspected to play a role in low back pain (LBP). The nociceptors in the lumbar FCL may experience excessive deformation and generate pain signals. As such, understanding the mechanical behaviour of the FCL, as well as that of its underlying nerves, is critical if one hopes to understand its role in LBP. In this work, we constructed a multiscale structure-based finite-element (FE) model of a lumbar FCL on a spinal motion segment undergoing physiological motions of flexion, extension, ipsilateral and contralateral bending, and ipsilateral axial rotation. Our FE model was created for a generic FCL geometry by morphing a previously imaged FCL anatomy onto an existing generic motion segment model. The fibre organization of the FCL in our models was subject-specific based on previous analysis of six dissected specimens. The fibre structures from those specimens were mapped onto the FCL geometry on the motion segment. A motion segment model was used to determine vertebral kinematics under specified spinal loading conditions, providing boundary conditions for the FCL-only multiscale FE model. The solution of the FE model then provided detailed stress and strain fields within the tissue. Lastly, we used this computed strain field and our previous studies of deformation of nerves embedded in fibrous networks during simple deformations (e.g. uniaxial stretch, shear) to estimate the nerve deformation based on the local tissue strain and fibre alignment. Our results show that extension and ipsilateral bending result in largest strains of the lumbar FCL, while contralateral bending and flexion experience lowest strain values. Similar to strain trends, we calculated that the stretch of the microtubules of the nerves, as well as the forces exerted on the nerves' membrane are maximal for extension and ipsilateral bending, but the location within the FCL of peak microtubule stretch differed from that of peak membrane force.

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Yanikömer, Neslihan, Rahim Nabbi et Klaus Fischer-Appelt. « Impact of Radiation-Induced Microstructures on the Integrity of Spent Nuclear Fuel (SNF) Elements in Long-Term Storage ». Safety of Nuclear Waste Disposal 1 (10 novembre 2021) : 17–18. http://dx.doi.org/10.5194/sand-1-17-2021.

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Abstract. The current safety concept provides for a period in the range of 40 years for interim storage of spent fuel elements. Since the requirement for proof of safety for to up to 100 years arises, the integrity of the spent fuel elements in prolonged interim storage and long-term repositories is becoming a critical issue. In response to this safety matter, this study aims to assess the impact of radiation-induced microstructures on the mechanical properties of spent fuel elements, in order to provide reliable structural performance limits and safety margins. The physical processes involved in radiation damage and the effect of radiation damage on mechanical properties are inherently multiscalar and hierarchical. Damage evolution under irradiation begins at the atomic scale, with primary knock-on atoms (PKAs) resulting in displacement cascades (primary damage), followed by the defect clusters leading to microstructural deformations. In this context, we have developed and applied a multiscale simulation methodology consistent with the multistage damage mechanisms and the corresponding effects on the mechanical properties of spent fuel cladding and its integrity. Within the improved hierarchical modelling sequence, the effect of the radiation field on the fuel element cladding material (Zircalloy-4) is assessed using Monte Carlo methods. A molecular dynamics method is employed to model damage formation by PKAs and primary damage defect configurations. The formation of clusters and evolution of microstructures are simulated by extending the simulation sequence to a longer time scale with the kinetic Monte Carlo (KMC) method. Transferring the calculated radiation-induced microstructures into macroscopic quantities is ultimately decisive for the structural/mechanical behaviour and stability of the cladding material, and thus for long-term integrity of the spent fuel elements. Results of the multiscale modelling and simulations as well as a comparison with experimental results will be presented at the conference session.

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Klahr, Bruno, José Luís Medeiros Thiesen, Otávio Teixeira Pinto, Thiago André Carniel et Eduardo Alberto Fancello. « A variational RVE-based multiscale poromechanical formulation applied to soft biological tissues under large deformations ». European Journal of Mechanics - A/Solids 99 (mai 2023) : 104937. http://dx.doi.org/10.1016/j.euromechsol.2023.104937.

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XIAO, SHAOPING, et WEIXUAN YANG. « A NANOSCALE MESHFREE PARTICLE METHOD WITH THE IMPLEMENTATION OF THE QUASICONTINUUM METHOD ». International Journal of Computational Methods 02, n^o 03 (septembre 2005) : 293–313. http://dx.doi.org/10.1142/s0219876205000533.

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Since meshfree particle methods have advantages on simulating the problems involving extremely large deformations, fractures etc., they become attractive options to be used in the hierarchical multiscale modeling to approximate a large number of atoms. We propose a nanoscale meshfree particle method with the implementation of the quasicontinuum technique in this paper. The intrinsic properties of the material associated with each particle will be sought from the atomic level via the Cauchy-Born rule. The studies of a nano beam and a nano plate with a central crack show that such a hierarchical modeling can be beneficial from the advantages of meshfree particle methods.

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Li, Shaofan, et Wing Kam Liu. « Meshfree and particle methods and their applications ». Applied Mechanics Reviews 55, n^o 1 (1 janvier 2002) : 1–34. http://dx.doi.org/10.1115/1.1431547.

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Recent developments of meshfree and particle methods and their applications in applied mechanics are surveyed. Three major methodologies have been reviewed. First, smoothed particle hydrodynamics (SPH) is discussed as a representative of a non-local kernel, strong form collocation approach. Second, mesh-free Galerkin methods, which have been an active research area in recent years, are reviewed. Third, some applications of molecular dynamics (MD) in applied mechanics are discussed. The emphases of this survey are placed on simulations of finite deformations, fracture, strain localization of solids; incompressible as well as compressible flows; and applications of multiscale methods and nano-scale mechanics. This review article includes 397 references.

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Du, Li, Tong, Li et Liu. « Isothermal Drying Process and its Effect on Compressive Strength of Concrete in Multiscale ». Applied Sciences 9, n^o 19 (25 septembre 2019) : 4015. http://dx.doi.org/10.3390/app9194015.

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Drying could change the microstructure of cement-based materials and inevitably affect their mechanical properties. The isothermal drying process of concrete at three scales and its effect on compressive behavior and microstructure were investigated. The deformations of cement paste, mortar, and concrete in the drying process all exhibit the characteristics of expansion first and then shrinkage. The porosity and average pore diameter increase after drying, which is mainly attributed to the increase of pores less than 100 nm diameter for paste and to the pores within 100~1000 nm for mortar. Drying makes paste denser, while the bonding between paste and aggregate is weakened. Microstructural studies indicate that the increase in compressive strength of concrete caused by isothermal drying is the competition result between the strengthening effect and the weakening effect, and is related to the paste content.

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Klinge, Sandra, et Klaus Hackl. « APPLICATION OF THE MULTISCALE FEM TO THE DETERMINATION OF MACROSCOPIC DEFORMATIONS CAUSED BY DISSOLUTION-PRECIPITATION CREEP ». International Journal for Multiscale Computational Engineering 14, n^o 2 (2016) : 95–111. http://dx.doi.org/10.1615/intjmultcompeng.2016016021.

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Paran, S. M. R., G. Naderi, M. H. R. Ghoreishy et C. Dubois. « Multiscale modeling of polymer systems comprising nanotube-like inclusions by considering interfacial debonding under plastic deformations ». Composite Structures 194 (juin 2018) : 302–15. http://dx.doi.org/10.1016/j.compstruct.2018.03.059.

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Ma, Juan, Shahab Sahraee, Peter Wriggers et Laura De Lorenzis. « Stochastic multiscale homogenization analysis of heterogeneous materials under finite deformations with full uncertainty in the microstructure ». Computational Mechanics 55, n^o 5 (31 mars 2015) : 819–35. http://dx.doi.org/10.1007/s00466-015-1136-3.

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Ye, J. J., J. Xi, Y. Hong, Y. Li, C. C. Chu, H. Cai et Y. K. Wang. « A Multiscale Approach to Studying the High Strain-Rate Deformations of Glass-Fiber-Reinforced Polymer-Matrix Composites ». Mechanics of Composite Materials 55, n^o 5 (novembre 2019) : 607–16. http://dx.doi.org/10.1007/s11029-019-09837-6.

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Fablet, Ronan, Alexis Chaigneau et Sophie Bertrand. « Multiscale Analysis of Geometric Planar Deformations : Application to Wild Animal Electronic Tracking and Satellite Ocean Observation Data ». IEEE Transactions on Geoscience and Remote Sensing 52, n^o 6 (juin 2014) : 3627–36. http://dx.doi.org/10.1109/tgrs.2013.2274157.

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Huang, Xingyu, Jian Zhang, Kun Tang, Xinyu Cheng, Chen Ye et Lihui Wang. « Multilevel network for large deformation image registration based on feature consistency and flow normalization ». Medical Physics 51, n^o 12 (20 septembre 2024) : 8962–78. https://doi.org/10.1002/mp.17390.

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AbstractBackgroundDeformable image registration is an essential technique of medical image analysis, which plays important roles in several clinical applications. Existing deep learning‐based registration methods have already achieved promising performance for the registrations with small deformations, while it is still challenging to deal with the large deformation registration due to the limits of the image intensity‐similarity‐based objective function.PurposeTo achieve the image registration with large‐scale deformations, we proposed a multilevel network architecture FCNet to gradually refine the registration results based on semantic feature consistency constraint and flow normalization (FN) strategy.MethodsAt each level of FCNet, the architecture is mainly composed to a FeaExtractor, a FN module, and a spatial transformation module. FeaExtractor consists of three parallel streams which are used to extract the individual features of fixed and moving images, as well as their joint features, respectively. Using these features, the initial deformation field is estimated, which passes through a FN module to refine the deformation field based on the difference map of deformation filed between two adjacent levels. This allows the FCNet to progressively improve the registration performance. Finally, a spatial transformation module is used to get the warped image based on the deformation field. Moreover, in addition to the image intensity‐similarity‐based objective function, a semantic‐feature consistency constraint is also introduced, which can further promote the alignments by imposing the similarity between the fixed and warped image features. To validate the effectiveness of the proposed method, we compared our method with the state‐of‐the‐art methods on three different datasets. In EMPIRE10 dataset, 20, 3, and 7 fixed and moving 3D computer tomography (CT) image pairs were used for training, validation, and testing respectively; in IXI dataset, atlas to individual image registration task was performed, with 3D MR images of 408, 58, and 115 individuals were used for training, validation, and testing respectively; in the in‐house dataset, patient to atlas registration task was implemented, with the 3D MR images of 94, 3, and 15 individuals being training, validation, and testing sets, respectively.ResultsThe qualitative and quantitative comparison results demonstrated that the proposed method is beneficial for handling large deformation image registration problems, with the DSC and ASSD improved by at least 1.0% and 25.9% on EMPIRE10 dataset. The ablation experiments also verified the effectiveness of the proposed feature combination strategy, feature consistency constraint, and FN module.ConclusionsOur proposed FCNet enables multiscale registration from coarse to fine, surpassing existing SOTA registration methods and effectively handling long‐range spatial relationships.

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Golovina, N. Ya. « ALLOY AGING AS A MULTISCALE EFFECT WITHIN THE NANOCOMPOSITE THEORY ». PNRPU Mechanics Bulletin, n^o 6 (15 décembre 2023) : 50–56. http://dx.doi.org/10.15593/perm.mech/2023.6.05.

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Within the theory of finely dispersed nanocomposites, the dependence of the effective Young's modulus on the absolute size of the reinforcing particles is obtained. Two cases of controlling/changing the effective Young's modulus at a constant relative volume fraction of reinforcing particles are considered. The first is the disintegration of reinforcing particles into smaller ones, followed by diffusion throughout the volume of the matrix. In this case, the effective modulus of the nanocomposite increases. The second one is the agglomeration of reinforcing particles into larger ones. In this case, the effective modulus of the nanocomposite decreases. These patterns seem to be universal and independent of heat treatment technology. It can be assumed that the agglomeration or decomposition of the reinforcing particles depends on the choice of a heat treatment technology for a nanocomposite. It is important to emphasize that the selected heat treatment technology is to be such that during the heat treatment no phase transitions occur either in the material of the reinforcing particles or in the matrix material. It is necessary to eliminate the appearance of phase transitions, since the new phase represents a field of defects, in particular, the field of substitutional dislocations. For such processes, the gradient theory of a defect-free medium is no longer valid. It is necessary to build models of defective environments that are more complex. Therefore, this article does not consider the criteria for choosing a heat treatment technology. The question remains open that, along with the gradient generalization of the theory of composites, a nonlinear generalization is possible. Indeed, unlike ceramics, which retain physical linearity almost until destruction, metal composites exhibit plasticity over a large range of deformations. However, generalization to physical nonlinearity, and even more so to plasticity, is complicated by the fact that there is still no generally accepted theory for constructing a stress-strain curve even for homogeneous materials.

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Gupta, Raj K., X. Gary Tan, Mahadevabharath R. Somayaji et Andrzej J. Przekwas. « Multiscale Modelling of Blast-Induced TBI Mechanobiology - From Body to Neuron to Molecule ». Defence Life Science Journal 2, n^o 1 (29 mars 2017) : 3. http://dx.doi.org/10.14429/dlsj.2.10369.

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Blast induced Traumatic Brain Injury (bTBI) has become a signature wound of the recent military operations and is becoming a significant factor of recent civilian blast explosion events. In spite of significant clinical and preclinical research on TBI, current understanding of injury mechanisms is limited and little is known about the short and long-term outcomes. Mathematical models of bTBI may provide capabilities to study brain injury mechanisms, perhaps accelerating the development of neuroprotective strategies and aiding in the development of improved personal protective equipment. The paper presents a novel multiscale simulation framework that couples the body/brain scale biomechanics with micro-scale mechanobiology to study the effects of “primary” micro-damage to neuro-axonal structures with the “secondary” injury and repair mechanisms. Our results show that oligodendrocyte myelinating processes distribute strains among neighbor axons and cause their off-axis deformations. Similar effects have been observed at the finer scale for the Tau-Microtubule interaction. The paper also discusses the need for coupled modeling of primary injury biomechanics, secondary injury mechanobiology and model based assessment of injury severity scores. A new integrated computational and experimental approach is described coupling micro-scale injury criteria for the primary micro-mechanical damage to brain tissue/cells as well as to investigate various secondary injury mechanisms.

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Sagindykov, T. B., A. R. Brazhe et D. V. Sorokin. « PREPROCESSING AND REGISTRATION OF MINISCOPE-BASED CALCIUM IMAGING OF THE RODENT BRAIN ». ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-2/W12 (9 mai 2019) : 185–88. http://dx.doi.org/10.5194/isprs-archives-xlii-2-w12-185-2019.

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Abstract. Microscopic imaging is central to the brain and cognition studies in animals and often requires advanced image processing. In vivo recordings on awake behaving animals require stabilization of the images as the tissue in the images undergoes non-rigid deformations due to animal movement, pulse beat and breathing of the animal. Here we propose an approach to compensation for the tissue motion in calcium imaging data acquired with miniaturized wearable microscopes (miniscopes) from live rodent brains. Our approach includes preprocessing of the images in which we compensate for non-uniform illumination, remove calcium transients and instrument-specific noise. For image registration we use the multiscale mutual information based non-rigid algorithm with B-spline transformation model. We present the preliminary results of such motion compensation approach applied to the real miniscope image stacks.

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Binder, Eva, Wit Derkowski et Thomas K. Bader. « Development of Creep Deformations during Service Life : A Comparison of CLT and TCC Floor Constructions ». Buildings 12, n^o 2 (19 février 2022) : 239. http://dx.doi.org/10.3390/buildings12020239.

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Cross-laminated timber (CLT) slabs in residential buildings need additional weight, e.g., in the form of screeds or gravel layers, to fulfill the criterion for the highest impact-sound class. The additional mass is, however, not exploited for the load bearing behavior, but adds additional weight and leads to an increased height of the floor construction. In this study, such a CLT floor construction with a construction height of 380 mm is compared with a composite slab consisting of a CLT plate with a concrete layer on top with a floor construction height of 330 mm. The timber concrete composite (TCC) slab has a different creep behavior than the CLT slab. Thus, the development of the time-dependent deflections over the service life are of interest. A straightforward hybrid approach is developed, which exploits advanced multiscale-based material models for the individual composite layers and a standardized structural analysis method for the structural slab to model its linear creep behavior. The introduced approach allows to investigate load redistribution between the layers of the composite structure and the evolution of the deflection of the slab during the service life. The investigated slab types show a similar deflection after 50 years, while the development of the deflections over time are different. The CLT slab has a smaller overall stiffness at the beginning but a smaller decrease in stiffness over time than the investigated TCC slab.

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Ogata, Shuji, et Takahiro Igarashi. « Concurrent Coupling of Electronic-Density-Functional, Molecular Dynamics, and Coarse-Grained Particles Schemes for Multiscale Simulation of Nanostructured Materials ». Materials Science Forum 502 (décembre 2005) : 33–38. http://dx.doi.org/10.4028/www.scientific.net/msf.502.33.

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Feature sizes of useful electronic devices are becoming smaller and reaching nanometer ranges. There is increasing demand to perform dynamic simulations of such nano-devices with realistic sizes. To date, various kinds of simulation methods have been used for materials and devices including the density-functional theory (DFT) and the molecular dynamics (MD) for atomistic mechanics and the finite element method for continuum mechanics. We review recent progresses in our multiscale, hybrid simulation schemes that combine those methods. The coarse-grained particles (CG) method originally proposed by Rudd and Broughton [Phys. Rev. B58 (1998), p. R5893] has features suitable to such hybridization. We improve the CG method so that it is applicable to realistic nanostructured materials with large deformations. A novel hybridization scheme that couples the DFT method with the MD method is presented, which is applicable to virtually any selection of the DFT region in a wide range of materials. Hybrid DFT-MD simulations of the H2O reaction with nanostructured Si and alumina systems under stresses are performed, to demonstrate significant effects of stress on the chemical reaction.

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Gasparetto, Victor E. L., et Mostafa S. A. ElSayed. « Multiscale Modelling and Mechanical Anisotropy of Periodic Cellular Solids with Rigid-Jointed Truss-Like Microscopic Architecture ». Applied Mechanics 2, n^o 2 (1 juin 2021) : 331–55. http://dx.doi.org/10.3390/applmech2020020.

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This paper investigates the macroscopic anisotropic behavior of periodic cellular solids with rigid-jointed microscopic truss-like architecture. A theoretical matrix-based procedure is presented to calculate the homogenized stiffness and strength properties of the material which is validated experimentally. The procedure consists of four main steps, namely, (i) using classical structural analysis to determine the stiffness properties of a lattice unit cell, (ii) employing the Bloch’s theorem to generate the irreducible representation of the infinite lattice, (iii) resorting to the Cauchy–Born Hypothesis to express the microscopic nodal forces and deformations in terms of a homogeneous macroscopic strain field applied to the lattice, and (iv) employing the Hill–Mandel homogenization principle to obtain the macro-stiffness properties of the lattice topologies. The presented model is used to investigate the anisotropic mechanical behavior of 13 2D periodic cellular solids. The results are documented in three set of charts that show (i) the change of the Young and Shear moduli of the material with respect to their relative density; (ii) the contribution of the bending stiffness of microscopic cell elements to the homogenized macroscopic stiffness of the material; and (iii) polar diagrams of the change of the elastic moduli of the cellular solid in response to direction of macroscopic loading. The three set of charts can be used for design purposes in assemblies involving the honeycomb structures as it may help in selecting the best lattice topology for a given functional stiffness and strength requirement. The theoretical model was experimentally validated by means of tensile tests performed in additively manufactured Lattice Material (LM) specimens, achieving good agreement between the results. It was observed that the model of rigid-joined LM (RJLM) predicts the homogenized mechanical properties of the LM with higher accuracy compared to those predicted by pin-jointed models.

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