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 ▲]

Hyperspectral imaging applications in agriculture and agro-food product quality and safety control: A review

in Applied Spectroscopy Reviews (2013), 48(2), 142-159

In this review, various applications of Near Infrared Hyperspectral Imaging (NIR-HSI) in agriculture and in the quality control of agro-food products are presented. NIR-HSI is an emerging technique that ... [more ▼]

In this review, various applications of Near Infrared Hyperspectral Imaging (NIR-HSI) in agriculture and in the quality control of agro-food products are presented. NIR-HSI is an emerging technique that combines classical NIR spectroscopy and imaging techniques in order to simultaneously obtain spectral and spatial information from a field or a sample. The technique is non-destructive, non-polluting, fast and relatively inexpensive per analysis. Currently, its applications in agriculture range from vegetation mapping, crop disease, stress and yield detection to component identification in plants and impurity detection. There is growing interest in HSI for the safety and quality assessment of agro-food products. The applications have been classified from the level of satellite images to the macroscopic, if not, molecular level. [less ▲]

Techno-economic survey of Organic Rankine Cycle (ORC) systems

in Renewable & Sustainable Energy Reviews (2013), 22

New heat conversion technologies need to be developed and improved to take advantage of the necessary increase in the supply of renewable energy. The Organic Rankine Cycle is well suited for these ... [more ▼]

New heat conversion technologies need to be developed and improved to take advantage of the necessary increase in the supply of renewable energy. The Organic Rankine Cycle is well suited for these applications, mainly because of its ability to recover low-grade heat and the possibility to be implemented in decentralized lower-capacity power plants. In This paper, an overview of the different ORC applications is presented. A market review is proposed including cost figures for several commercial ORC modules and manufacturers. An in-depth analysis of the technical challenges related to the technology, such as working fluid selection and expansion machine issues is then reported. Technological constraints and optimization methods are extensively described and discussed. Finally, the current trends in research and development for the next generation of Organic Rankine Cycles are presented. [less ▲]

Maladie hémolytique néonatale modérée due à un anti‐RH46

Poster (2013, June)

Le potentiel du saule pour la phytostabilisation des sols pollués par les éléments-traces métalliques

Doctoral thesis (2013)

Since the ‘80s, when the concept of phytoremediation first appeared, a lot of research has been put into studying the efficiency of woody plants in metal extraction. Willows, as fast growing plants and ... [more ▼]

Since the ‘80s, when the concept of phytoremediation first appeared, a lot of research has been put into studying the efficiency of woody plants in metal extraction. Willows, as fast growing plants and because of their tolerance to difficult edaphic conditions, have been particularly well investigated. In this investigation, the essays were done on Salix clones, which come from a Walloon collection provided by ECOLIRI and ECOLIRIMED projects. The first objective was to study the potential of these local clones by considering not only their ability to extract their pollutants, but also by adding their biomass production to this parameter. We have called the study of these criteria the phenotypic approach to the tolerance of Salix clones to metals. The second added value of this investigation lies in the second objective which aims to complete these phenotypic criteria with physiological and proteomic criteria. These last criteria are often used to study the metal tolerance of plant species, but rarely for willows. The combination of these different approaches gives a expand view of metal tolerance in Salix clones studied in this investigation. As the phenotypical parameters help to answer the extraction ability challenge, the physiological and proteomic approaches give answers linked to the “health” of the willow trees when they grow in the presence of metals. Our results indicate that the clones that produced more biomass were the ones that showed the highest metal concentrations. The clones with lower biomass production showed the same tolerance as the highest producers and our results revealed that growth reduction indicates metal tolerance. Finally, after comparing our results of the metal concentrations obtained in the twigs, to results obtained during the last two decades of research papers, we have concluded that we should reconsider the use of Salix potential in phytoextraction. The first chapter of this investigation was about Salix clones exposed to metals, but, in natural conditions, their roots are colonized by fungi. Thus, their rhizosphere constitutes a separate ecosystem, which is interesting to investigate. The rhizospheric fungi, the first interface between roots and soil pollutants, play an important role in metal tolerance in woody plants. For this reason, the second chapter of this thesis aimed to test the in vitro growth of rhizospheric fungi collected on woody plant roots in the presence of cadmium. The outcome of these essays is that fungal strains have been identified and classified as tolerant to this metal. This chapter thus constitutes a first step in a future study aiming to analyze these strains in association with woody plant roots in the presence of metals. [less ▲]

Hygrothermal behavior modeling of different Lime-Hemp Concrete mixes

Conference (2013, May 27)

This paper studies the specific hygrothermal behavior of Lime-Hemp concretes through analysis of non-linear coupled heat and moisture transfer using a research model. Three compositions were studied ... [more ▼]

This paper studies the specific hygrothermal behavior of Lime-Hemp concretes through analysis of non-linear coupled heat and moisture transfer using a research model. Three compositions were studied, varying the type of binder. First Moisture Buffer Value determination tests are lead experimentally using the NORDTEST protocol. These dynamic experiments, which reveal the moisture storage and exchange capacity together with latent heat effects, are then modeled using a set of partial differential equations. The reduction of humidity buffering capacity induced by hydraulic binder incorporation is properly evaluated and the hygrothermal parameters can be assessed by inverse modeling. [less ▲]

MOA-2010-BLG-311: A planetary candidate below the threshold of reliable detection

in Astrophysical Journal (2013), 769(1), 77

We analyze MOA-2010-BLG-311, a high magnification (A_max>600) microlensing event with complete data coverage over the peak, making it very sensitive to planetary signals. We fit this event with both a ... [more ▼]

We analyze MOA-2010-BLG-311, a high magnification (A_max>600) microlensing event with complete data coverage over the peak, making it very sensitive to planetary signals. We fit this event with both a point lens and a 2-body lens model and find that the 2-body lens model is a better fit but with only Delta chi^2~140. The preferred mass ratio between the lens star and its companion is $q=10^(-3.7+/-0.1), placing the candidate companion in the planetary regime. Despite the formal significance of the planet, we show that because of systematics in the data the evidence for a planetary companion to the lens is too tenuous to claim a secure detection. When combined with analyses of other high-magnification events, this event helps empirically define the threshold for reliable planet detection in high-magnification events, which remains an open question. [less ▲]

Laboratory demonstration of a mid-infrared AGPM vector vortex coronagraph

in Astronomy and Astrophysics (2013), 553

Coronagraphy is a powerful technique to achieve high contrast imaging and hence to image faint companions around bright targets. Various concepts have been used in the visible and near-infrared regimes ... [more ▼]

Coronagraphy is a powerful technique to achieve high contrast imaging and hence to image faint companions around bright targets. Various concepts have been used in the visible and near-infrared regimes, while coronagraphic applications in the mid-infrared remain nowadays largely unexplored. Vector vortex phase masks based on concentric subwavelength gratings show great promise for such applications. We aim at producing and validating the first high-performance broadband focal plane phase mask coronagraphs for applications in the mid-infrared regime, and in particular the L band with a fractional bandwidth of ~16% (3.5-4.1 \mu m). Based on rigorous coupled wave analysis, we designed an annular groove phase mask (AGPM) producing a vortex effect in the L band, and etched it onto a series of diamond substrates. The grating parameters were measured by means of scanning electron microscopy. The resulting components were then tested on a mid-infrared coronagraphic test bench. A broadband raw null depth of 2 x 10^{-3} was obtained for our best L-band AGPM after only a few iterations between design and manufacturing. This corresponds to a raw contrast of about 6 x 10^{-5} (10.5 mag) at 2\lambda/D. This result is fully in line with our projections based on rigorous coupled wave analysis modeling, using the measured grating parameters. The sensitivity to tilt and focus has also been evaluated. After years of technological developments, mid-infrared vector vortex coronagraphs finally become a reality and live up to our expectations. Based on their measured performance, our L-band AGPMs are now ready to open a new parameter space in exoplanet imaging at major ground-based observatories. [less ▲]

What is the right pathway to be sustainable? Case of biofuels and bioproducts in Europe

Conference (2013, May 15)

The International Liquid Mirror Telescope project: optical quality tests and prospective detection of multiply imaged quasars

Doctoral thesis (2013)

The International Liquid Mirror Telescope (ILMT) project is a joint collaboration between different universities and research institutes in Belgium, Canada, India and Poland, for the design, construction ... [more ▼]

The International Liquid Mirror Telescope (ILMT) project is a joint collaboration between different universities and research institutes in Belgium, Canada, India and Poland, for the design, construction and operation of a 4 meter liquid mirror telescope at the Devasthal Observatory (India). In the framework of the present thesis, we have contributed to the development of the ILMT. We have namely designed and manufactured an innovative instru- ment capable of measuring the optical quality of the primary mirror that may be affected by the propagation of wavelets on the mercury layer. The instrument is composed of a laser source, emitting a beam whose reflection on the mirror is modulated by slope variations induced by the wavelets. Preliminary tests were carried out showing the validity of the method for on site testing of the mirror. The ILMT has been designed to perform a photometric variability survey of a narrow strip of sky, making it very suitable for the detection and follow-up of photometrically variable sources such as supernovae and quasars. In the second part of this thesis, we present an estimate of the number of QSOs to be detected within the ILMT survey, and of the expected number of multiply imaged sources among these caused by the presence of a deflector near the lines-of- sight. We have studied the impact of various parameters on the expected number of detected gravitational lens systems, such as the instrumental resolution of the telescope, the galaxy population type(s) and corresponding lensing model(s), and the cosmological parameters. The statistical sample of multiply imaged QSOs is intended to be used as a cosmological probe. In order to make a sensitivity comparison between vari- ous modelling approaches, we introduce a new formalism to estimate the lensing probabilities, based on the joined probability density of the observed QSOs. This new formalism allows to calculate three probability densities: that asso- ciated with the optical depth distribution, as well as those related to the deflector and the lensed source redshift distributions. For the case of FLRW universes, we compare the sensitivity of these distributions as a function of the cosmological mass density. [less ▲]