Ivens J.,Lessius University College Antwerp |
Ivens J.,Catholic University of Leuven |
Urbanus M.,Catholic University of Leuven |
De Smet C.,University College Ghent
Express Polymer Letters | Year: 2011
A shape memory polymer (SMP) can be deformed from a permanent to a temporary shape above their transformation temperature. Upon reheating, the SMP spontaneously returns to the permanent shape. SMP's show high deformability, but the recovery stresses are very low, thus limiting the size of the components. This paper presents the first results of an ongoing research to develop large sized components based on SMP. To achieve higher recovery stresses, asymmetric fibre reinforced shape memory composites were produced (SMPC) using resin transfer moulding. The results show a 30- fold increase in recovery stress, compared to the neat SMP resin. The recovery stress is independent of the deformation temperature, but is strongly affected by the degree of deformation. At higher deformation levels, crazing occurs. Even though the visible effects of the crazing disappear during reheating, it does influence the recovery stress. This indicates that the ability to recover the permanent shape might change in cyclic loading. All composites tested show complete recovery upon reheating. The rate of shape recovery is higher when the fibre reinforcement is loaded in compression. © BME-PT.
Jacquemyn H.,Catholic University of Leuven |
Honnay O.,Catholic University of Leuven |
Cammue B.P.A.,Catholic University of Leuven |
Brys R.,Research Institute for Nature and Forest |
And 2 more authors.
Molecular Ecology | Year: 2010
Most orchid species rely on mycorrhizae to complete their life cycle. Despite a growing body of literature identifying orchid mycorrhizal associations, the nature and specificity of the association between orchid species and mycorrhizal fungi remains largely an open question. Nonetheless, better insights into these obligate plant-fungus associations are indispensable for understanding the biology and conservation of orchid populations. To investigate orchid mycorrhizal associations in five species of the genus Orchis (O. anthropophora, O. mascula, O. militaris, O. purpurea, and O. simia), we developed internal transcribed spacer-based DNA arrays from extensive clone library sequence data sets, enabling rapid and simultaneous detection of a wide range of basidiomycetous mycorrhizal fungi. A low degree of specificity was observed, with two orchid species associating with nine different fungal partners. Phylogenetic analysis revealed that the majority of Orchis mycorrhizal fungi are members of the Tulasnellaceae, but in some plants, members of the Thelephoraceae, Cortinariaceae and Ceratobasidiaceae were also found. In all species except one (O. mascula), individual plants associated with more than one fungus simultaneously, and in some cases, associations with ≥3 mycorrhizal fungi at the same time were identified. Nestedness analysis showed that orchid mycorrhizal associations were significantly nested, suggesting asymmetric specialization and a dense core of interactions created by symmetric interactions between generalist species. Our results add support to the growing literature that multiple associations may be common among orchids. Low specificity or preference for a widespread fungal symbiont may partly explain the wide distribution of the investigated species. © 2010 Blackwell Publishing Ltd.
Demurie E.,Ghent University |
Roeyers H.,Ghent University |
Baeyens D.,Lessius University College Antwerp |
Sonuga-Barke E.,Ghent University |
Sonuga-Barke E.,University of Southampton
Journal of Child Psychology and Psychiatry and Allied Disciplines | Year: 2011
Background: Children with attention deficit/hyperactivity disorder (ADHD) display abnormalities in reward processing. Most reward studies have focused on the effects of material or monetary rewards. Studies with autism spectrum disorder (ASD) have focused on social rewards. In this study we compared the effects of amount and type of reward in children with ADHD and those with ASD. Methods: Two adapted versions of the Monetary Incentive Delay Task were used to study the effects of monetary and social reward anticipation on performance in 40 typically developing (TD) children and adolescents (8-16y), 35 children and adolescents with ADHD and 31 children and adolescents with ASD. Results: Monetary and social reward improved accuracy and response time (RT) in all groups. The higher the anticipated reward, the more accurate and faster were responses. Independent of these effects, there was a differential effect of reward type. Both clinical groups, but not TD, responded faster for monetary than social rewards. Conclusions: The results, while not supporting hyposensitivity to changes in reward amount in ADHD and ASD, do suggest that both groups are generally less motivated in settings where social as opposed to monetary rewards can be earned. © 2011 Association for Child and Adolescent Mental Health.
Kohler C.,Maastricht University |
Breugelmans E.,Lessius University College Antwerp |
Breugelmans E.,Catholic University of Leuven |
Dellaert B.G.C.,Erasmus University Rotterdam
Journal of Management Information Systems | Year: 2011
Interactive decision aids (IDAs) typically use concrete, feature-based approaches to interact with consumers. Recently, however, interaction designs that focus on communicating abstract consumer needs have been suggested as a promising alternative. This paper investigates how temporal distance moderates the effectiveness of these two competing IDA communication designs by its effect on consumers' mental representation of the product decision problem. Temporal distance is inherently connected to IDAs in two ways. Congruency between consumption timing (immediate versus distant) and IDA communication design (concrete versus abstract, respectively) increases the likelihood to accept the IDA's advice. This effect is also achieved by congruency between IDA process timing (immediate versus delayed delivery of recommendations) and IDA communication design (concrete versus abstract, respectively). We further show that this process is mediated by the perceived transparency of the IDA process. Managers and researchers need to take into account the importance of congruency between the user and the interface through which companies interact with their users and can further optimize IDAs so that they better match consumers' mental representations. © 2011 M.E. Sharpe, Inc.
Soetens T.,Ghent University |
Van Gysel A.,Lessius University College Antwerp |
Matthys S.,Ghent University |
Taerwe L.,Ghent University
Construction and Building Materials | Year: 2013
The residual post-cracking tensile strength of conventional steel fibre reinforced concrete is directly related to both the amount of fibres crossing a crack and the individual pull-out responses of all activated fibres. Therefore, the knowledge of the single pull-out behaviour is essential to understand the uni-axial or bending behaviour of SFRC when it is considered as a full-fledged composite. Since hooked-end steel fibres are considered to be the most suitable fibre type for structural purposes, the need to accurately predict the pull-out response of these type of fibres, is of great practical importance. In this paper, an experimental investigation of the pull-out response of both straight and hooked-end steel fibres is discussed. Based on the obtained experimental data, a semi-analytical model is developed to predict the fibre pull-out behaviour. The ability of the model to deal with different geometrical and mechanical fibre characteristics as well as the influence of orientation, embedded length and matrix compressive strengths, reflects its overall quality. © 2013 Elsevier Ltd. All rights reserved.
Goossens L.,Ghent University |
Braet C.,Ghent University |
Bosmans G.,Katholieke University Leuven andreas Vesaliusstraat 2 |
Decaluwe V.,Lessius University College Antwerp
Eating Behaviors | Year: 2011
Objective: The present study aimed to add to the limited literature on the role of self-esteem and attachment for the explanation of loss of control over eating (LC) among pre-adolescent boys and girls. Method: Self-report questionnaires were administered to a community sample of 555 children (8-11. years; 47% female). Results: Children reporting LC (17.6% of the sample) were characterized by a lower self-esteem and less secure attachment toward both of their parents. No gender differences emerged. Moreover, the relation between self-esteem and LC was fully mediated by attachment toward mother and partially mediated by attachment toward father. Discussion: The present study provides preliminary evidence for the idea that the influence of self-esteem on LC seems to operate through a third variable that is an insecure relationship with the parents. Longitudinal research is needed to further elucidate the influence of interpersonal factors on the development of LC. © 2011 Elsevier Ltd.
Snoeys L.,Catholic University of Leuven |
Vanhoof G.,University Hospitals Leuven |
Manders E.,Catholic University of Leuven |
Manders E.,Lessius University College Antwerp
Disability and Rehabilitation | Year: 2013
Purpose: to explore and describe the health care situation, the use of aids, the way of communicating and the quality of life of Locked-in syndrome patients in Flanders (Belgium) and to collect information on their fulfilled and unfulfilled needs. Method: in depth interviews with eight LIS-patients by means of an extensive questionnaire consisting of five parts: (i) general information and medical history, (ii) health care, rehabilitation and follow-up, (iii) speech and communication, (iv) quality of life, (v) needs and problems experienced. Results: the patients' condition, mostly caused by ischemic stroke, persisted for a mean period of 6 years 8 months. Their mean age was 41;10 years. At the moment of our study all the patients were living at home. Care was provided by an extensive care team. Some recovery of head and neck movements was mentioned, recovery of upper and lower limb mobility however was very limited. Most patients use an alphabet system to communicate, all of them had access to and made use of a PC with internet connection. Except for the domain of physical functioning, the quality of life scores of our patient group are rather high. As for unfulfilled needs, half of the patients experience a lack of information on their condition and a lack of appropriate information on (communication) aids. Conclusion: most results seem to be in line with those of other studies, though larger scale and follow-up studies are needed to confirm these findings. Implications for Rehabilitation Access to a personal computer with internet connection is very important for LIS-patients and thus should be provided. LIS-patients feel the need for more and better adapted information on LIS and on available aids. Most chronic LIS-patients feel the need for extensive, multidisciplinary and continued care. © 2013 Informa UK, Ltd.
Boudt K.,Catholic University of Leuven |
Boudt K.,Lessius University College Antwerp |
Cornelissen J.,Catholic University of Leuven |
Croux C.,Catholic University of Leuven
Statistics and Computing | Year: 2012
The Gaussian rank correlation equals the usual correlation coefficient computed from the normal scores of the data. Although its influence function is unbounded, it still has attractive robustness properties. In particular, its breakdown point is above 12%. Moreover, the estimator is consistent and asymptotically efficient at the normal distribution. The correlation matrix obtained from pairwise Gaussian rank correlations is always positive semidefinite, and very easy to compute, also in high dimensions. We compare the properties of the Gaussian rank correlation with the popular Kendall and Spearman correlation measures. A simulation study confirms the good efficiency and robustness properties of the Gaussian rank correlation. In the empirical application, we show how it can be used for multivariate outlier detection based on robust principal component analysis. © 2011 Springer Science+Business Media, LLC.
Boudt K.,Catholic University of Leuven |
Boudt K.,Lessius University College Antwerp |
Croux C.,Catholic University of Leuven
Computational Statistics and Data Analysis | Year: 2010
The Gaussian quasi-maximum likelihood estimator of Multivariate GARCH models is shown to be very sensitive to outliers in the data. A class of robust M-estimators for MGARCH models is developed. To increase the robustness of the estimators, the use of volatility models with the property of bounded innovation propagation is recommended. The Monte Carlo study and an empirical application to stock returns document the good robustness properties of the M-estimator with a fat-tailed Student t loss function. © 2009 Elsevier B.V. All rights reserved.
Opgenhaffen M.,Lessius University College Antwerp |
Opgenhaffen M.,Catholic University of Leuven
First Monday | Year: 2011
This paper argues for not studying the Web as one, homogeneous medium, but instead as a meta-medium that carries various divergent news media like news blogs, discussion forums, Web TV, and RSS news feeds, each with a specific presentation style. Based on a content analysis of Flemish online news media, the level of multimedia, interactivity and hypertext of different divergent news platforms are identified. Results suggest that multiple online platforms are used to present the news, even within meta-media like digital newspapers or portal sites. This analysis also reveals that the use of online news features varies among divergent news platforms, some being innovative and others rather traditional.