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.
Swolfs Y.,Kasteelpark Arenberg |
Crauwels L.,Kasteelpark Arenberg |
Breda E.V.,Kasteelpark Arenberg |
Gorbatikh L.,Kasteelpark Arenberg |
And 3 more authors.
Composites Part A: Applied Science and Manufacturing | Year: 2014
To improve the toughness of carbon fibre composites, unidirectional carbon fibre prepregs were hybridised with highly oriented polypropylene (PP) tapes. The latter tapes are used in self-reinforced PP composites (SRPPs) with high toughness, but relatively low stiffness. The tensile behaviour of intralayer hybrids of oriented PP tapes and CFPP prepreg tapes was investigated by changing the layup and weave pattern, and by adding interleaved PP films. While stiffness and strength of these hybrids was decreased compared to CFPP, their ductility significantly increased by adding oriented PP tapes. The parallel behaviour of the two constituent materials was caused by delaminations, which developed after the CFPP failure and spreads over the entire sample. This behaviour was modelled and proven to be independent of layup and weave pattern. Interleaved films, which are often necessary for thermoformability, limited the delamination development by increasing the interlayer bonding and yielded a lower ultimate failure strain. © 2014 Elsevier Ltd. All rights reserved.
Allacker K.,Kasteelpark Arenberg |
De Nocker L.,Kasteelpark Arenberg
Journal of Industrial Ecology | Year: 2012
This article describes an approach developed to estimate the environmental external costs of the Belgian building sector. Several existing methods and related data sets for determining the monetary value of environmental impacts were reviewed and compared in light of their relevance to an impact assessment of the construction sector. This study concludes that the methods available consider different impacts and differ substantially in monetary values for identical impacts. A harmonized and transparent method is recommended to improve the feasibility and acceptance of internalizing external costs; agreement on the impacts to be assessed and their external costs based on current insights is important. Here, a new method is proposed for a life cycle impact assessment-based valuation of environmental external costs for application to the Belgian building sector. To enable a comprehensive assessment, it became clear that solely considering "key" pollutants is insufficient. Although this article focuses on the development and not on the implementation of the method proposed, implementation revealed that the life cycle environmental external cost of new buildings (meeting current insulation standards or better) is relatively small compared to the life cycle financial cost. © 2012 by Yale University.
Van Den Broeck L.,Celestijnenlaan |
Diehl M.,Kasteelpark Arenberg |
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.
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.
Alzate C.,Kasteelpark Arenberg |
Suykens J.A.K.,Kasteelpark Arenberg
Proceedings of the 18th European Symposium on Artificial Neural Networks - Computational Intelligence and Machine Learning, ESANN 2010 | Year: 2010
Kernel spectral clustering has been formulated as a primal - dual optimization setting allowing natural extensions to out-of-sample data together with model selection in a learning framework which is important for obtaining a good generalization performance. In this paper, we propose a new sparse method for kernel spectral clustering. The approach exploits the structure of the eigenvectors and the corresponding projections of the data when the clusters are well formed. Experimental results with toy data and images show highly sparse clustering models with predictive capabilities.
De Brabanter K.,Kasteelpark Arenberg |
De Brabanter J.,Kasteelpark Arenberg |
De Moor B.,Kasteelpark Arenberg |
Gijbels I.,Catholic University of Leuven
Journal of Machine Learning Research | Year: 2013
We present a fully automated framework to estimate derivatives nonparametrically without estimating the regression function. Derivative estimation plays an important role in the exploration of structures in curves (jump detection and discontinuities), comparison of regression curves, analysis of human growth data, etc. Hence, the study of estimating derivatives is ecually important as regression estimation itself. Via empirical derivatives we approximate the cth order derivative and create a new data set which can be smoothed by any nonparametric regression estimator. We derive L1 and L2 rates and establish consistency of the estimator. The new data sets created by this technicue are no longer independent and identically distributed (i.i.d.) random variables anymore. As a consecuence, automated model selection criteria (data-driven procedures) break down. Therefore, we propose a simple factor method, based on bimodal kernels, to effectively deal with correlated data in the local polynomial regression framework. © 2013 Kris De Brabanter, Jos De Brabanter, Bart De Moor and Irene Gijbels.
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.
Roels S.,Kasteelpark Arenberg |
Deurinck M.,Kasteelpark Arenberg
Building and Environment | Year: 2011
The influence of the emissivity of a roof underlay on the global thermal behaviour of sloped roofs is investigated. Five well-insulated pitched roofs have been constructed in a test building. The five roofs have a south-west and north-east-oriented pitch and differ in long wave emissivity of the underlay. All roofs are equipped with thermocouples and heat fluxes sensors to evaluate the thermal response of the roofs to the climatic conditions. Both summer and winter conditions have been measured. In addition to the in situ evaluation, a laboratory experiment was set-up to evaluate the influence of the emissivity of the underlay on the summer behaviour of a sloped roof under fixed boundary conditions. With thermocouples and heat flux sensors at different heights in the roof the effect of the reflective foil on the heat gain to the inside could be evaluated. The measured data are compared with a simple numerical model that accounts for the buoyancy effects in the ventilated cavity between tiles and underlay. Laboratory experiments and simulations revealed that a low emissivity of the underlay decreases the heat gain to the indoor environment, but that due to the thermal stack flow in the air cavity underneath the tiles, the advantage of a reflective foil mainly plays a role in the bottom part of the roof. In the in situ measurements it was found that workmanship, airtightness and wind and thermal stack effects are much more important and disturb the possible benefits of using a reflective underlay. © 2010 Elsevier Ltd.
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.