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See detailThree-dimensional crack initiation, propagation, branching and junction in non-linear materials by an extended meshfree method without asymptotic enrichment
Bordas, Stéphane UL; Rabczuk, Timon; Zi, Goangseup

in Engineering Fracture Mechanics (2008), 75(5), 943-960

This paper presents a three-dimensional, extrinsically enriched meshfree method for initiation, branching, growth and coalescence of an arbitrary number of cracks in non-linear solids including large ... [more ▼]

This paper presents a three-dimensional, extrinsically enriched meshfree method for initiation, branching, growth and coalescence of an arbitrary number of cracks in non-linear solids including large deformations, for statics and dynamics. The novelty of the methodology is that only an extrinsic discontinuous enrichment and no near-tip enrichment is required. Instead, a Lagrange multiplier field is added along the crack front to close the crack. This decreases the computational cost and removes difficulties involved with a branch enrichment. The results are compared to experimental data, and other simulations from the literature to show the robustness and accuracy of the method. [less ▲]

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See detailThree-Dimensional Crack Propagation with Global Enrichment XFEM and Vector Level Sets
Agathos, Konstantinos; Ventura, Giulio; Chatzi, Eleni et al

Scientific Conference (2015)

Detailed reference viewed: 162 (4 UL)
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See detailA three-dimensional meshfree method for continuous multiple-crack initiation, propagation and junction in statics and dynamics
Rabczuk, Timon; Bordas, Stéphane UL; Zi, Goangseup

in Computational Mechanics (2007), 40(3), 473-495

This paper proposes a three-dimensional meshfree method for arbitrary crack initiation and propagation that ensures crack path continuity for non-linear material models and cohesive laws. The method is ... [more ▼]

This paper proposes a three-dimensional meshfree method for arbitrary crack initiation and propagation that ensures crack path continuity for non-linear material models and cohesive laws. The method is based on a local partition of unity. An extrinsic enrichment of the meshfree shape functions is used with discontinuous and near-front branch functions to close the crack front and improve accuracy. The crack is hereby modeled as a jump in the displacement field. The initiation and propagation of a crack is determined by the loss of hyperbolicity or the loss of material stability criterion. The method is applied to several static, quasi-static and dynamic crack problems. The numerical results very precisely replicate available experimental and analytical results. [less ▲]

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See detailTHREE-DIMENSIONAL MICROFLUIDIC CELL CULTURE OF STEM CELL-DERIVED NEURONAL MODELS OF PARKINSON'S DISEASE
Lucumi-Moreno, Edinson UL

Doctoral thesis (2016)

Cell culture models in 3D have become an essential tool for the implementation of cellular models of neurodegenerative diseases. Parkinson’s disease (PD) is characterized by the loss of dopaminergic ... [more ▼]

Cell culture models in 3D have become an essential tool for the implementation of cellular models of neurodegenerative diseases. Parkinson’s disease (PD) is characterized by the loss of dopaminergic neurons from the substantia nigra. The study of PD at the cellular level requires a cellular model that recapitulates the complexity of those neurons affected in PD. Induced Pluripotent Stem Cells (iPSC) technology is an efficient method for the derivation of dopaminergic neurons from human neuroepithelial stem cells (hNESC), hence proving to be a suitable tool to develop cellular models of PD. To obtain DA neurons from hNESC in a 3D culture, a protocol based on the use of small molecules and growth factors was implemented in a microfluidic device (OrganoPlate). This non PDMS device is based on the use of phaseguide (capillary pressure barriers that guide the liquid air interface) technology and the hydrogel matrigel as an extra cellular matrix surrogate. To characterize the morphological features and the electrophysiological activity of wild type hNESCs differentiated neuronal population, with those differentiated neurons carrying the LRRK2 mutation G2019S, a calcium imaging assay based on the use of a calcium sensitive dye (Fluo-4) and image analysis methods, were implemented. Additionally, several aspects of fluid flow dynamics, rheological properties of matrigel and its use as surrogate extracellular matrix were investigated. Final characterization of the differentiated neuronal population was done using an immunostaining assay and microscopy techniques. The yields of differentiated dopaminergic neurons in the 2 lane OrganoPlate were in the range of 13% to 27%. Morphological (length of processes) and electrophysiological (firing patterns) characteristics of wild type differentiated neurons and those carrying the LRRK2 mutation G2019S, were determined applying an image analysis pipeline. Velocity profiles and shear stress of fluorescent beads in matrigel flowing in culture lanes of the 2 lane OrganoPlate, were estimated using particle image velocimetry techniques. In this thesis, we integrate two new technologies to establish a new in vitro 3D cell based model to study several aspects of PD at the cellular level, aiming to establish a microfluidic cell culture experimental platform to study PD, using a systems biology approach. [less ▲]

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See detailA three-dimensional movement analysis of the spike in fistball
Bund, Andreas UL; Ghorbani, Saeed; Rathjens, Franziska

in Sports (2016), 4(4), 1-12

Due to its relevancy to point scoring, the spike is considered as one of the most important skills in fistball. Biomechanical analyses of this sport are very rare. In the present study, we performed a ... [more ▼]

Due to its relevancy to point scoring, the spike is considered as one of the most important skills in fistball. Biomechanical analyses of this sport are very rare. In the present study, we performed a three-dimensional kinematic analysis of the fistball spike, which helps to specify performance parameters on a descriptive level. Recorded by four synchronized cameras (120 Hz) and linked to the motion capture software Simi Motion® 5.0, three female fistball players of the second German league (24–26 years, 1.63–1.69 m) performed several spikes under standardized conditions. Results show that the segment velocities of the arm reached their maximum successively from proximal to distal, following the principle of temporal coordination of single impulses. The wrist shows maximum speed when the fist hits the ball. The elbow joint angle performs a rapid transition from a strong flexion to a (almost) full extension; however, the extension is completed after the moment of ball impact. In contrast, the shoulder joint angle increases almost linearly until the fistball contact and decreases afterward. The findings can be used to optimize the training of the spike. [less ▲]

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See detailThree-dimensional non-linear fracture mechanics by enriched meshfree methods without asymptotic enrichment
Bordas, Stéphane UL; Zi, G.; Rabczuk, T.

in Proceedings of the IUTAM Symposium on Discretization Methods for Evolving Discontinuities (2007)

This paper presents a three-dimensional, extrinsically enriched meshfree method for initiation, growth and coalescence of an arbitrary number of cracks in non-linear solids including large deformations ... [more ▼]

This paper presents a three-dimensional, extrinsically enriched meshfree method for initiation, growth and coalescence of an arbitrary number of cracks in non-linear solids including large deformations, for statics and dynamics. The novelty of the methodology fashioned in this work is that only an extrinsic discontinuous enrichment and no near-tip/asymptotic enrichment is required. Instead, a Lagrange multiplier field is added along the crack front to close the crack along the front. This decreases the computational cost and removes difficulties involved with a branch enrichment. Numerical examples treated include the pull-out of a reinforcement bar from a concrete block, and a Taylor bar impact with very large deformation and fragmentation. The results are compared to experimental results, and other simulations from the literature, which shows the robustness and accuracy of the method. © 2007 Springer. [less ▲]

Detailed reference viewed: 107 (0 UL)
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See detailA Three-Dimensional Remeshed Hybrid Smooth Particle-mesh Method
Obeidat, Anas UL

Scientific Conference (2016, June 10)

Detailed reference viewed: 72 (18 UL)
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See detailThree-dimensional remeshed smoothed particle hydrodynamics for the simulation of isotropic turbulence
Obeidat, Anas UL; Bordas, Stéphane UL

in INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS (2017)

We present a remeshed particle-mesh method for the simulation of three-dimensional compressible turbulent flow. The method is related to the mesh free smoothed particle hydrodynamic (SPH) method, but the ... [more ▼]

We present a remeshed particle-mesh method for the simulation of three-dimensional compressible turbulent flow. The method is related to the mesh free smoothed particle hydrodynamic (SPH) method, but the present method introduces a mesh for efficient calculation of the pressure gradient, and laminar and turbulent diffusion. In addition, the mesh is used to remesh (reorganise uniformly) the particles to ensure a regular particle distribution and convergence of the method. The accuracy of the presented methodology is tested for a number of benchmark problems involving two- and three-dimensional Taylor-Green flow, thin double shear layer, and three-dimensional isotropic turbulence. Two models were implemented, direct numerical simulations, and Smagorinsky model. Taking advantage of the Lagrangian advection, and the finite difference efficiency, the method is capable of providing quality simulations while maintaining its robustness and versatility [less ▲]

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See detailThree-dimensional remeshed smoothed particle hydrodynamics for the simulation of isotropic turbulence
Obeidat, Anas UL; Bordas, Stéphane UL

in International Journal for Numerical Methods in Fluids (2017)

We present a remeshed particle-mesh method for the simulation of three-dimensional compressible turbulent flow. The method is related to the mesh free smoothed particle hydrodynamic (SPH) method, but the ... [more ▼]

We present a remeshed particle-mesh method for the simulation of three-dimensional compressible turbulent flow. The method is related to the mesh free smoothed particle hydrodynamic (SPH) method, but the present method introduces a mesh for efficient calculation of the pressure gradient, and laminar and turbulent diffusion. In addition, the mesh is used to remesh (reorganise uniformly) the particles to ensure a regular particle distribution and convergence of the method. The accuracy of the presented methodology is tested for a number of benchmark problems involving two- and three-dimensional Taylor-Green flow, thin double shear layer, and three-dimensional isotropic turbulence. Two models were implemented, direct numerical simulations, and Smagorinsky model. Taking advantage of the Lagrangian advection, and the finite difference efficiency, the method is capable of providing quality simulations while maintaining its robustness and versatility [less ▲]

Detailed reference viewed: 83 (10 UL)
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See detailThree-dimensional structural view of the central metabolic network of Thermotoga maritima.
Zhang, Ying; Thiele, Ines UL; Weekes, Dana et al

in Science (New York, N.Y.) (2009), 325(5947), 1544-1549

Metabolic pathways have traditionally been described in terms of biochemical reactions and metabolites. With the use of structural genomics and systems biology, we generated a three-dimensional ... [more ▼]

Metabolic pathways have traditionally been described in terms of biochemical reactions and metabolites. With the use of structural genomics and systems biology, we generated a three-dimensional reconstruction of the central metabolic network of the bacterium Thermotoga maritima. The network encompassed 478 proteins, of which 120 were determined by experiment and 358 were modeled. Structural analysis revealed that proteins forming the network are dominated by a small number (only 182) of basic shapes (folds) performing diverse but mostly related functions. Most of these folds are already present in the essential core (approximately 30%) of the network, and its expansion by nonessential proteins is achieved with relatively few additional folds. Thus, integration of structural data with networks analysis generates insight into the function, mechanism, and evolution of biological networks. [less ▲]

Detailed reference viewed: 58 (5 UL)
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See detailA three-way multidimensional scaling approach to the analysis of judgments about persons
Krolak-Schwerdt, Sabine UL

in Weihs, C.; Gaul, W. (Eds.) Studies in classification, data analysis and knowledge organization (2005)

Judgments about persons may depend on (1) how coherently person at- tributes are linked within the stimulus person and (2) how strongly the given person information activates a social stereotype. These ... [more ▼]

Judgments about persons may depend on (1) how coherently person at- tributes are linked within the stimulus person and (2) how strongly the given person information activates a social stereotype. These factors may determine the number of judgment dimensions, their salience and their relatedness. A three-way multi- dimensional scaling model is presented that measures these parameters and their change across stimulus persons or judgment conditions. The proposed approach in- volves a formal modelling of information integration in the judgment process. An application to experimental data shows the validity of the model. [less ▲]

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See detailThree-way multidimensional scaling: Comparing the validity of methods
Krolak-Schwerdt, Sabine UL

Scientific Conference (2006, March)

Detailed reference viewed: 7 (1 UL)
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See detailThree-way multidimensional scaling: Formal properties and relationships between scaling methods
Krolak-Schwerdt, Sabine UL

in Baier, D.; Decker, R.; Schmidt-Thieme, L. (Eds.) Studies in classification, data analysis and knowledge organization: Data analysis and decision support (2005)

This paper is concerned with methods of three-way two-mode multi- dimensional scaling which were developed for the joint analysis of a number of promities matrices. The classi¯cation of these methods into ... [more ▼]

This paper is concerned with methods of three-way two-mode multi- dimensional scaling which were developed for the joint analysis of a number of promities matrices. The classi¯cation of these methods into trilinear and quadrilin- ear models (Kruskal (1983)) is outlined, and it is shown, that a number of speci¯c properties and interpretations are associated with this classi¯cation the methods within each class have in common. Finally, relationships of the methods within and between the two model classes are outlined. [less ▲]

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See detailThreshold for potential sputtering of LiF
Hayderer, G.; Schmid, M.; Varga, P. et al

in Physical Review Letters (1999), 83(19), 3948-3951

We have measured total sputtering yields for impact of slow (less than or equal to 100 eV) singly and doubly charged ions on LiF. The minimum potential energy necessary to induce potential sputtering (PS ... [more ▼]

We have measured total sputtering yields for impact of slow (less than or equal to 100 eV) singly and doubly charged ions on LiF. The minimum potential energy necessary to induce potential sputtering (PS) from UF was determined to be about 10 eV. This threshold coincides with the energy necessary to produce a cold hole in the valence band of LiF by resonant neutralization. This allows the first unambiguous identification of PS induced by cold holes. Further stepwise increase of the sputtering yield with higher projectile potential energies provides evidence for additional defect-mediated sputtering mechanisms operative in alkali halides. [less ▲]

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See detailThe Threshold of Exhibition Venues: Access to the World of Culture
Schall, Céline UL

in Wille, Christian; Reckinger, Rachel (Eds.) Exploring Constructions of Space and Identity in Border Regions (2015)

Detailed reference viewed: 45 (8 UL)
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See detailThreshold preferences and the environment
Schumacher, Ingmar; Zou, Benteng UL

in Journal of Mathematical Economics (2015), 60

In this article we study the implication of thresholds in preferences. To model this we extend the basic model of John and Pecchenino (1994) by allowing the current level of environmental quality to have ... [more ▼]

In this article we study the implication of thresholds in preferences. To model this we extend the basic model of John and Pecchenino (1994) by allowing the current level of environmental quality to have a discrete impact on how an agent trades off future consumption and environmental quality. Thus, we endogenize the semi-elasticity of utility based on a step function. We find that for low (high) thresholds, environmental quality converges to a low (high) steady state. For intermediate levels it converges to a stable p-cycle, with environmental quality being asymptotically bounded below and above by the low and high steady state. As policy implications we study shifts in the threshold. Costless shifts of the threshold are always worthwhile. If it is costly to change the threshold, then it is worthwhile to change the threshold if the threshold originally was sufficiently low. Lump-sum taxes lead to a development trap and a proportional income tax should be preferred. [less ▲]

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See detailThreshold Preferences and the Environment
Schumacher, Ingmar; Zou, Benteng UL

E-print/Working paper (2013)

In this article we study the implication of thresholds in preferences. To model this we extend the basic model of John and Pecchenino (1994) by allowing the current level of environmental quality to have ... [more ▼]

In this article we study the implication of thresholds in preferences. To model this we extend the basic model of John and Pecchenino (1994) by allowing the current level of environmental quality to have a discrete impact on how an agent trades o future consumption and environmental quality. In other words, we endogenize the semi-elasticity of utility based on a step function. We motivate the existence of the threshold based on research from political science, from arguments based on regulation and standards, cultural economics as well as ecological economics. Our results are that the location of the threshold determines both the potential steady states as well as the dynamics. For low (high) thresholds, environmental quality converges to a low (high) steady state. For intermediate levels it converges to a stable p-cycle, with environmental quality being asymptotically bounded below and above by the low and high steady state. We discuss implications for intergenerational equity and policy making. As policy implications we study shifts in the threshold. Our results are that, in case it is costless to shift the threshold, it is always worthwhile to do so. If it is costly to change the threshold, then it is worthwhile to change the threshold if the threshold originally was suffi ciently low. Lump-sum taxes may lead to a development trap and should be avoided if there are uncertainties about the threshold or the effectiveness of the policy. [less ▲]

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See detailThrough a century of change: portrait of a pragmatic visionary
Danescu, Elena UL

in Journal of European Integration History = Zeitschrift für Geschichte der Europäischen Integration = Revue d'Histoire de l'Intégration Européenne (2018)

As Prime Minister and Finance Minister of Luxembourg over several decades, Pierre Werner shaped the future of his country and was one of the rare statesmen to play a part in the progress of European ... [more ▼]

As Prime Minister and Finance Minister of Luxembourg over several decades, Pierre Werner shaped the future of his country and was one of the rare statesmen to play a part in the progress of European integration until the mid-1980s. He played a major role in regional integration (BLEU, Benelux) and in EEC policy-making and gained a strong reputation for forging a political consensus between larger powers (Germany and France)and between diametrically opposed positions (‘economists’ vs ‘monetarists’). In this way he succeeded in defending Luxembourg’s vital interests, from the financial centre to the seats of the European institutions. Werner was involved in the major ideological debates of the time. Although initially in favour of a monetary approach, Werner was one of the first to develop arguments for a symmetrical economic and monetary union. [less ▲]

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See detailThrough the Spherical Looking-Glass: Asymmetry Enables Multicolored Internal Reflection in Cholesteric Liquid Crystal Shells
Geng, Yong UL; Jang, Ju-Hyun; Noh, Kyung-Gyu et al

in Advanced Optical Materials (2017), 6(1), 1700923

Spheres of cholesteric liquid crystal generate dynamic patterns due to selec- tive reflection from a helical structure subject to continuously curved bounda- ries. So far the patterns are investigated ... [more ▼]

Spheres of cholesteric liquid crystal generate dynamic patterns due to selec- tive reflection from a helical structure subject to continuously curved bounda- ries. So far the patterns are investigated exclusively as function of reflections at the sphere exterior. Here it is shown that the cholesteric shells in a microfluidics produced double emulsion enable also a sequence of internal reflections if the shells have sufficiently thin top and thick bottom. While such asymmetry is promoted by buoyancy when the internal droplet has lower density than the liquid crystal, the elasticity of the cholesteric helix prefers a symmetric shell geometry, acting against gravity. This subtle balance can hide the internal reflections for long time. Eventually, however, the asymmetry is established, revealing a new class of photonic patterns characterized by colored sharp concentric rings. With the complete knowledge of the diverse light-reflecting behavior of cholesteric liquid crystal shells, and utilizing the tunability of the structure period by, e.g., temperature, electric field, or expo- sure to various chemical species as well as polymer stabilization for making the shells long-term stable, they may be developed into remarkable new optical elements for photonics, sensing, or security pattern generation. [less ▲]

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See detailThrough-the-Wall Radar Imaging for Heterogeneous Walls using Compressive Sensing
Lagunas, Eva UL; Amin, Moeness; Ahmad, Fauzia

in International Workshop on Compressed Sensing Theory and its Applications to Radar, Sonar and Remote Sensing (CoSeRa), Pisa, Italy, 16-19 June 2015 (2015, June)

Detailed reference viewed: 92 (2 UL)