Equivalence of weighted likelihood and Jeffreys modal estimation of proficiency under polytomous item response models

Conference (2013, July 23)

This talk focuses on two proficiency level estimators in item response theory (IRT) framework: the weighted likelihood estimator (WLE) and the Jeffreys modal estimator (JME), that is, the usual Bayes ... [more ▼]

This talk focuses on two proficiency level estimators in item response theory (IRT) framework: the weighted likelihood estimator (WLE) and the Jeffreys modal estimator (JME), that is, the usual Bayes modal estimator with Jeffreys’ non-informative prior. With dichotomously scored items, the WLE and the JME are completely equivalent under the two-parameter logistic model, while remarkable relationships were established under the three-parameter logistic model. The purpose of this talk is to extend such comparison to polytomously scored items. It is shown that both WLE and JME are also equivalent for two broad classes of polytomous IRT models, including, among others, the (modified) graded response model, the (generalized) partial credit model, the rating scale model and the nominal response model. Parallelisms with dichotomously scored items are drawn. An example from a real data set is used to illustrate this finding. [less ▲]

The influence of verbal descriptions on face identification in children and adults

Poster (2013, July 12)

Investigation on a ventilation heat recovery exchanger: Modeling and experimental validation in dry and partially wet conditions

in Energy & Buildings (2013), 62

The present paper focuses on the development and experimental validation of a model of air-to-air heat exchanger dedicated to domestic mechanical heat recovery ventilation. The proposed model describes ... [more ▼]

The present paper focuses on the development and experimental validation of a model of air-to-air heat exchanger dedicated to domestic mechanical heat recovery ventilation. The proposed model describes dry and partially wet regimes. The first part of the paper presents a semi-empirical model based on the physical characteristics of the heat recovery device and relying on empirical correlations available in the literature for the convective heat transfer coefficients. In the case of partially wet regime, a moving boundary model is applied in order to predict sensible and latent heat transfer rates. A model developed with friction factor coefficients estimated by correlations from the literature is also presented in order to predict the hydraulic performance in dry conditions. The second part of the paper describes the experimental investigation conducted on an off-the-shelf heat exchanger. Experimental data are used to tune correlations for the determination of the convective heat transfer coefficient and validate the proposed simulation model of the ventilation heat recovery exchanger in partially wet conditions. The model developed to determine the hydraulic performance with existing correlations for the friction factor coefficient does not require a calibration. Finally, examples of use of the developed model are presented, which includes coupling the model with a building simulation model, a study of the influence of the humidity on the evolution of the latent and sensible heat transfer rates and strategies to avoid freezing in the heat exchanger. [less ▲]

Fifth International Conference on Advanced COmputational Methods in ENgineering (ACOMEN 2011)

in International Journal of Computational & Applied Mathematics (2013), 246

Study on alternative approaches to corrosion protection of ballast tanks using an economic model

in Marine Structures (2013)

One of the most relevant problems in ship construction and maintenance nowadays is corrosion in ballast tanks of modern merchant vessels. On the one hand, there is a general consensus that the economic ... [more ▼]

One of the most relevant problems in ship construction and maintenance nowadays is corrosion in ballast tanks of modern merchant vessels. On the one hand, there is a general consensus that the economic lifespan of such a vessel depends, to a large degree, upon the corrosion state of its ballast tanks, while on the other hand these ballast tanks, located between the outer hull and the cargo tanks, makes routine inspection and maintenance a difficult task. Today, ship's ballast tanks are usually constructed in steel and protected with an epoxy coating backed up by sacrificial zinc anodes. Such a construction has been applied without significant alterations for many years. The objective of this economic study is to compare this construction method with some potential alternatives. The considered alternatives are: (1) an increase in structural scantlings, eliminating the necessity to replace corroded at a cost of real cargo carrying capacity of the ship, (2) application of the novel and more durable TSCF25 coating (3), the use of corrosion resistant steel in ship construction and (4) a standard PSPC15 coating combined with lifetime lasting aluminum sacrificial anodes. A cost model was used to evaluate these alternative options together with sensitivity analysis. It is concluded that the durable coating and the use of lifetime lasting aluminum anodes are bound to improve the actual basic tank concept. Corrosion resistant steel becomes attractive when the steel price becomes competitive. [less ▲]

Bacillus subtilis as a tool for screening soil metagenomic libraries for antimicrobial activities

in Journal of Microbiology and Biotechnology (2013), 23(6),

Modeling of Electromagnetic Systems by Coupling of Subproblems – Application to Thin Shell Finite Element Magnetic Models

Doctoral thesis (2013)

The direct application of the finite element method to realistic electromagnetic problems is challenging, especially when modeling structures with thin conductive and/or magnetic parts. This work presents ... [more ▼]

The direct application of the finite element method to realistic electromagnetic problems is challenging, especially when modeling structures with thin conductive and/or magnetic parts. This work presents a subproblem method for correcting the inaccuracies inherent to classical thin shell models, and to efficiently handle geometrical and material variations in parametric studies. [less ▲]

Multiscale computational homogenization methods with a gradient enhanced scheme based on the discontinuous Galerkin formulation

in Computer Methods in Applied Mechanics & Engineering (2013), 260

When considering problems of dimensions close to the characteristic length of the material, the size e ects can not be neglected and the classical (so–called first–order) multiscale computational ... [more ▼]

When considering problems of dimensions close to the characteristic length of the material, the size e ects can not be neglected and the classical (so–called first–order) multiscale computational homogenization scheme (FMCH) looses accuracy, motivating the use of a second–order multiscale computational homogenization (SMCH) scheme. This second–order scheme uses the classical continuum at the micro–scale while considering second–order continuum at the macro–scale. Although the theoretical background of the second–order continuum is increasing, the implementation into a finite element code is not straightforward because of the lack of high–order continuity of the shape functions. In this work, we propose a SMCH scheme relying on the discontinuous Galerkin (DG) method at the macro–scale, which simplifies the implementation of the method. Indeed, the DG method is a generalization of weak formulations allowing for inter-element discontinuities either at the C0 level or at the C1 level, and it can thus be used to constrain weakly the C1 continuity at the macro–scale. The C0 continuity can be either weakly constrained by using the DG method or strongly constrained by using usual C0 displacement–based finite elements. Therefore, two formulations can be used at the macro–scale: (i) the full–discontinuous Galerkin formulation (FDG) with weak C0 and C1 continuity enforcements, and (ii) the enriched discontinuous Galerkin formulation (EDG) with high–order term enrichment into the conventional C0 finite element framework. The micro–problem is formulated in terms of standard equilibrium and periodic boundary conditions. A parallel implementation in three dimensions for non–linear finite deformation problems is developed, showing that the proposed method can be integrated into conventional finite element codes in a straightforward and e cient way. [less ▲]

"Rends excellente ta place de l'Occident". Pour une approche intégrée de la décoration des tombes thébaines sous le règne d'Amenhotep II

Doctoral thesis (2013)

Sur l’ensemble des règnes de la XVIIIème dynastie égyptienne, il apparaît, jusqu’assez récemment, que celui d’Amenhotep II a suscité un intérêt moindre de la part des chercheurs, ces derniers lui ayant ... [more ▼]

Sur l’ensemble des règnes de la XVIIIème dynastie égyptienne, il apparaît, jusqu’assez récemment, que celui d’Amenhotep II a suscité un intérêt moindre de la part des chercheurs, ces derniers lui ayant préféré, de manière générale, ceux plus longs ou historiquement plus déterminants de Thoutmosis III, d’Amenhotep III ou encore d’Amenhotep IV – Akhenaton, et ce bien que plusieurs travaux fondamentaux aient déjà permis de mettre en évidence une série de traits spécifiques à cette période. Le règne d’Amenhotep II se caractérise en effet par une nouvelle gestion du gouvernement, où le phénomène d’hérédité qui s’installait progressivement dans certaines fonctions est endigué mais où, dans le même temps, les membres de quelques familles puissantes et particulièrement proches du roi se voient confier les plus hautes charges de l’administration. Aussi, pour la réalisation de leurs « demeures d’éternité », véritables cartes de visite de leurs propriétaires et témoins privilégiés des grandes orientations de l’époque, les principaux officiels du règne d’Amenhotep II ont pour la plupart porté leur choix sur la partie supérieure de la colline de Sheikh Abd el-Gourna, site particulièrement prisé pour sa position surélevée comme pour la proximité qu’il entretient avec les temples funéraires royaux. Les tombes de ces dignitaires se distinguent néanmoins de celles de leurs prédécesseurs, par des dimensions colossales, par l’étendue et la complexité des dispositifs intérieurs ainsi que par le choix de représentations et d’inscriptions qui, placées à des endroits stratégiques, soulignent les relations étroites qu’entretenait le propriétaire avec Pharaon. En outre, le traitement même des scènes figurées est également, à ce moment précis, l’objet de modifications considérables ; l’art pictural, qui se voulait depuis ses origines purement conceptuel et d’apparence hiéroglyphique, s’assouplit à divers égards pour prendre une apparence plus « sensuelle », plus « perceptuelle ». Ces transformations, qui s’amplifieront encore durant les règnes suivants, jettent déjà, en quelque sorte, les bases de ce qui deviendra la « révolution » du règne d’Akhenaton. Dans ce contexte, la présente thèse vise, au moyen d’une analyse pluridisciplinaire et « intégrée » de la décoration des chapelles du règne d’Amenhotep II, à caractériser dans une perspective socioculturelle les changements iconographiques et stylistiques qui affectent cette production artistique en pleine mutation. [less ▲]

Influence of the mode of walk on walking speed in multiple sclerosis: are you walking comfortably?

Poster (2013, June 10)

Introduction : Walking speed (WS) is the most frequent gait variable taken into account when measuring gait dysfunction in neurological diseases. Influences of the mode of walk instructed to the subject ... [more ▼]

Introduction : Walking speed (WS) is the most frequent gait variable taken into account when measuring gait dysfunction in neurological diseases. Influences of the mode of walk instructed to the subject, i.e. « as fast as possible » (AFAP) or « at a comfortable pace » (PrP) have not been well characterized in multiple sclerosis (MS). Objectives : to compare those 2 mode of walk in a population of persons with MS (pMS) and healthy volunteers (HV). Methods: WS was measured with a new automated device along a 25 foot distance (T25FW) as part of a multimodal evaluation of gait in an MS ambulatory department. Results: Baseline demographics between HV and pMS were comparable. Our first results demonstrate that (i) WS is obviously significantly higher in AFAP than in PrP both for pMS and HV (p < 0.001 for all comparisons) and (ii) the relative difference between AFAP and PrP WS is significantly higher in HV than in pMS (p < 0.001). The AFAP-PrP WS correlation is higher in pMS (r = 0.87, p < 0.001) than in HV (r = 0.51, p < 0.001). Finally, the relative difference between AFAP and PrP WS is significantly and negatively correlated with the PrP WS in HV (r = -0.41, p < 0.001) and pMS with mild to moderate disability (EDSS 0-3.5, r = -0.49, p < 0.01) but not in pMS with high disability (EDSS 4-5.5, r = 0.008). Conclusions : these results suggests that heatlhy subjects have access to a higher range of PrP WS than pMS and questions the regulation of PrP WS that might be under psychological or behavioural influences. The demonstration of a lower PrP-AFAP difference in MS suggests that pMS are either adopting a natural WS closer to their maximum WS, or alternatively that they can’t reach their maximum WS because of neurological impairments. Our results also emphasize the importance of the instructed mode of walk in the quantification of gait disorders both for routine clinical practice and clinical trials. [less ▲]