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Leuven, Belgium

Demol J.,Celestijnenlaan | Lambrechts D.,Celestijnenlaan | Geris L.,Celestijnenlaan | Schrooten J.,Kasteelpark Arenberg | Van Oosterwyck H.,Celestijnenlaan
Biomaterials | Year: 2011

The in vitro culture of hydrogel-based constructs above a critical size is accompanied by problems of unequal cell distribution when diffusion is the primary mode of oxygen transfer. In this study, an experimentally-informed mathematical model was developed to relate cell proliferation and death inside fibrin hydrogels to the local oxygen tension in a quantitative manner. The predictive capacity of the resulting model was tested by comparing its outcomes to the density, distribution and viability of human periosteum derived cells (hPDCs) that were cultured inside fibrin hydrogels in vitro. The model was able to reproduce important experimental findings, such as the formation of a multilayered cell sheet at the hydrogel periphery and the occurrence of a cell density gradient throughout the hydrogel. In addition, the model demonstrated that cell culture in fibrin hydrogels can lead to complete anoxia in the centre of the hydrogel for realistic values of oxygen diffusion and consumption. A sensitivity analysis also identified these two parameters, together with the proliferation parameters of the encapsulated cells, as the governing parameters for the occurrence of anoxia. In conclusion, this study indicates that mathematical models can help to better understand oxygen transport limitations and its influence on cell behaviour during the in vitro culture of cell-seeded hydrogels. © 2010 Elsevier Ltd. Source

Audenaert J.,Ghent University | Durinck G.,Ghent University | Leloup F.B.,Ghent University | Deconinck G.,Kasteelpark Arenberg | Hanselaer P.,Ghent University
Optics Express | Year: 2013

Ray files offer a very accurate description of the optical characteristics of a light source. This is essential whenever optical components are positioned in close proximity (near-field) of the light source in order to perform accurate ray tracing simulations. However, a ray file does not allow for a direct simulation of the spatial luminance distribution, i.e. luminance map, by off-the-shelf ray tracers. Simulating luminance maps of light sources or luminaires is especially important in general lighting in order to predict their general perception when viewed by the observer, and more specific, the perception of glare of luminaires having a non-uniform luminance distribution. To enable the simulation of luminance maps while maintaining the high accuracy offered by a ray file, a sampling method is presented. To validate the approach, near-field goniophotometer measurements of two planar light sources were performed. From these measurement data, ray files were extracted to which the sampling method was applied in order to obtain a set of surface sources. This approach was validated by comparing measured luminance images with simulated luminance images. A good agreement was found, validating the presented method. ©2013 Optical Society of America. Source

Van Humbeeck J.,Kasteelpark Arenberg
Materials Research Bulletin | Year: 2012

This papers summarizes the alloys systems in which a martensitic transformation at high transformation temperatures occurs with potentials for shape memory effect. © 2012 Elsevier Ltd. All rights reserved. Source

Francois S.,Kasteelpark Arenberg | Schevenels M.,Kasteelpark Arenberg | Galvin P.,Kasteelpark Arenberg | Galvin P.,Polytechnic University of Valencia | And 2 more authors.
Computer Methods in Applied Mechanics and Engineering | Year: 2010

This paper presents a general 2.5D coupled finite element-boundary element methodology for the computation of the dynamic interaction between a layered soil and structures with a longitudinally invariant geometry, such as railway tracks, roads, tunnels, dams, and pipelines. The classical 2.5D finite element method is combined with a novel 2.5D boundary element method. A regularized 2.5D boundary integral equation is derived that avoids the evaluation of singular traction integrals. The 2.5D Green's functions of a layered halfspace, computed with the direct stiffness method, are used in a boundary element method formulation. This avoids meshing of the free surface and the layer interfaces with boundary elements and effectively reduces the computational efforts and storage requirements. The proposed technique is applied to four examples: a road on the surface of a halfspace, a tunnel embedded in a layered halfspace, a dike on a halfspace and a vibration isolating screen in the soil. © 2010 Elsevier B.V. Source

Van Den Broeck L.,Celestijnenlaan | Diehl M.,Kasteelpark Arenberg | Swevers J.,Celestijnenlaan
Mechatronics | Year: 2011

This paper presents a new model predictive control method for time-optimal point-to-point motion control of mechatronic systems. The formulation of time-optimal behavior within the model predictive control framework and the structure of the underlying optimization problem are discussed and modifications are presented in order to decrease the computational load of the numerical solution method such that sampling rates in the millisecond range and long prediction horizons for large point-to-point motions are feasible. An extensive experimental validation on a linear motor drive and an overhead crane setup demonstrates the advantages of the developed time-optimal model predictive control approach in comparison with traditional model predictive control. © 2011 Elsevier Ltd. All rights reserved. Source

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