Elastic-Net Regularization in Learning Theory

Within the framework of statistical learning theory we analyze in detail the so-called elastic-net regularization scheme proposed by Zou and Hastie for the selection of groups of correlated variables. To investigate on the statistical properties of this scheme and in particular on its consistency properties, we set up a suitable mathematical framework. Our setting is random-design regression where we allow the response variable to be vector-valued and we consider prediction functions which are linear combination of elements ({\em features}) in an infinite-dimensional dictionary. Under the assumption that the regression function admits a sparse representation on the dictionary, we prove that there exists a particular ``{\em elastic-net representation}'' of the regression function such that, if the number of data increases, the elastic-net estimator is consistent not only for prediction but also for variable/feature selection. Our results include finite-sample bounds and an adaptive scheme to select the regularization parameter. Moreover, using convex analysis tools, we derive an iterative thresholding algorithm for computing the elastic-net solution which is different from the optimization procedure originally proposed by Zou and HastieComment: 32 pages, 3 figure

Design principles for professionalizing primary school teachers on promoting reading motivation

Studies show that teachers’ continuing professional development (CPD) is essential for educational quality, and moreover, when it comes to reading, key for students’ success in education and participation in our 21st century society. Most of the research investigating professional development programs on improving teachers’ self-efficacy for teaching reading and in particular on fostering students’ reading motivation, however, fails to include clear and detailed descriptions of the design principles underlying the programs. Therefore, the present study provides a comprehensive description and operationalization of the design principles of a CPD program for primary school teachers focusing on promoting students’ reading motivation combining Desimone’s (2009) framework for effective professional development with Self-Determination Theory (Ryan & Deci, 2000). Consequently, the CPD program’s core features as distinguished by Desimone (i.e., content focus, coherence, active learning, collective participation and duration) and the need for autonomy, competence and relatedness as put central in SDT are analytically described and elaborated on. In view of reporting on the implementation check of the CPD, we further provide insight into whether these operationalized design principles were also perceived as such by the teachers participating in a first iteration of the CPD intervention. information

Optimization of the logistics of agricultural biogas plants = Optimalisatie van de logistiek bij mestvergistingsinstallaties

Within the framework of the EU-AGRO-BIOGAS project, the optimisation model Bioloco has been adapted for the application on biogas plants and was applied on a Dutch example case

Heart and Brain:The influence of affective and rational determinants in new venture teams: an empirical examination

Elfring, T. [Promotor]Khapova, S.N. [Promotor]Jansen, P.G.W. [Copromotor

Are we overusing IVF?

Peer reviewedPublisher PD

Nieuwe biomassaketens in Noord-Holland : Case 1 : Biomassavergassingsketen

Om na te gaan welke nieuwe biomassaketens tot ontwikkeling kunnen worden gebracht, zijn enkele mogelijke ketens doorgerekend met het computermodel Bioloco. Het doel hierbij is via een gestructureerde aanpak enkele regionale biomassaketens te identificeren die voldoende perspectief bieden op realisatie op korte termijn in de regio Noord-Holland. Voor de biomassaketens is uitgegaan van de biomassasoorten snoeiafval gemeenten, dunningshout bos, snoeihout fruittelers en stro. De conversietechniek is vergassing. Er zijn twee cases bekeken: basis case 1: een centrale vergasser van 40 MWth en basis case 2: twee decentrale vergassers van 20 MWth. Bij elke case zijn drie varianten bekeken: hogere inputcapaciteit, aangepaste prijzen en verminderde beschikbaarheid. De modeluitkomsten geven inzicht in 1) de kosten en opbrengsten (en winst), 2) het energieverbruik en de energieopbrengst en 3) de broeikasgasemissies en de vermeden broeikasgasemissies. De resultaten geven aan dat inzet van biomassa in een vergasser positief scoort, zowel financieel, energetisch als qua reductie van broeikasgasemissies. Er lijkt voldoende biomassa beschikbaar. Bij de kleinschaligere vergassers zijn de logistieke kosten lager, maar dat weegt niet op tegen de hogere conversiekosten

Toric intraocular lenses for correction of astigmatism in keratoconus and after corneal surgery

Purpose: To describe the results of cataract extraction with toric intraocular lens (IOL) implantation in patients with preexisting astigmatism from three corneal conditions (keratoconus, postkeratoplasty, and postpterygium surgery). Methods: Cataract patients with topographically stable, fairly regular (although sometimes very high) corneal astigmatism underwent phacoemulsification with implantation of a toric IOL (Zeiss AT TORBI 709, Alcon Acrysof IQ toric SN6AT, AMO Tecnis ZCT). Postoperative astigmatism and refractive outcomes, as well as visual acuities, vector reduction, and complications were recorded for all eyes. Results: This study evaluated 17 eyes of 16 patients with a mean age of 60 years at the time of surgery. Mean follow-up in this study was 12 months. The corrected distance Snellen visual acuity (with spectacles or contact lenses) 12 months postoperatively was 20/32 or better in 82% of eyes. The mean corneal astigmatism was 6.7 diopters (D) preoperatively, and 1.5 D of refractive cylinder at 1-year follow-up. No vision-compromising intra- or postoperative complications occurred and decentration or off-axis alignment of toric IOLs were not observed. Conclusion: Phacoemulsification with toric IOL implantation was a safe and effective procedure in the three mentioned corneal conditions. Patient selection, counseling, and IOL placement with optimal astigmatism correction are crucial

Behavioral motivations for self-insurance under different disaster risk insurance schemes

This paper presents a lab-in-the-field experiment with 2111 Dutch homeowners in floodplain areas to examine the impacts of financial incentives and behavioral motivations for self-insurance under different flood insurance schemes. We experimentally varied the insurance type (mandatory public versus voluntary private) and the availability of a premium discount incentive for investing in flood damage mitigation measures. This set-up allowed us to examine the existence of moral hazard, advantageous selection and the behavioral motivations of individual agents who face these different insurance types, without the selection bias that makes a causal inference from survey studies problematic. The main results show that a premium discount can increase investments in self-insurance under both private and public insurance. Moreover, we find no support for moral hazard in our natural disaster insurance market, but we do find a substantial share of cautious people who invest both in private insurance as well as in self-insurance, indicating advantageous selection. The results have implications for the design of insurance schemes to cope with increasing natural disaster risks