Last 7 days
Bookmark and Share    
Full Text
Peer Reviewed
See detailExperimental and numerical study of the flight of geese
Dimitriadis, Grigorios ULg; Gardiner, James; Tickle, Peter et al

in Aeronautical Journal (in press)

The flight of barnacle geese at airspeeds representing high-speed migrating flight is investigated using experiments and simulations. The experimental part of the work involved the filming of three ... [more ▼]

The flight of barnacle geese at airspeeds representing high-speed migrating flight is investigated using experiments and simulations. The experimental part of the work involved the filming of three barnacle geese (Branta Leucopsis) flying at different airspeeds in a wind tunnel. The video footage was analysed in order to extract the wing kinematics. Additional information, such as wing geometry and camber was obtained from a 3D scan of a dried wing. An unsteady vortex lattice method was used to simulate the aerodynamics of the measured flapping motion. The simulations were used in order to successfully reproduce the measured body motion and thus obtain estimates of the aerodynamic forces acting on the wings. It was found that the mean of the wing pitch angle variation with time has the most significant effect on lift while the difference in the durations of the upstroke and downstroke has the major effect on thrust. The power consumed by the aerodynamic forces was also estimated; it was found that increases in aerodynamic power correspond very closely to climbing motion and vice versa. Root-mean-square values of the power range from 100 W to 240 W. Finally, it was observed that tandem flying can be very expensive for the trailing bird. [less ▲]

Detailed reference viewed: 46 (4 ULg)
Full Text
Peer Reviewed
See detailDiversity patterns of the vascular plant group Zosterophyllopsida in relation to Devonian palaeogeography
Cascales - Miñana, Borja ULg; Meyer-Berthaud, Brigitte

in Palaeogeography, Palaeoclimatology, Palaeoecology (in press)

Detailed reference viewed: 7 (0 ULg)
See detailTasting the World. A Cultural History of Taste in the Early Modern Era
Von Hoffmann, Viktoria ULg

Book published by University of Illinois Press (in press)

Detailed reference viewed: 35 (6 ULg)
Full Text
Peer Reviewed
See detailWorking memory deficits in developmental dyscalculia: the importance of serial order.
Attout, Lucie ULg; Majerus, Steve ULg

in Child Neuropsychology : A Journal on Normal & Abnormal Development in Childhood & Adolescence (in press)

Detailed reference viewed: 41 (8 ULg)
Full Text
Peer Reviewed
See detailAnother Generalization of Abelian Equivalence: Binomial Complexity of Infinite Words (long version)
Rigo, Michel ULg; Salimov, Pavel

in Theoretical Computer Science (in press)

The binomial coefficient of two words $u$ and $v$ is the number of times $v$ occurs as a subsequence of $u$. Based on this classical notion, we introduce the $m$-binomial equivalence of two words refining ... [more ▼]

The binomial coefficient of two words $u$ and $v$ is the number of times $v$ occurs as a subsequence of $u$. Based on this classical notion, we introduce the $m$-binomial equivalence of two words refining the abelian equivalence. Two words $x$ and $y$ are $m$-binomially equivalent, if, for all words $v$ of length at most $m$, the binomial coefficients of $x$ and $v$ and respectively, $y$ and $v$ are equal. The $m$-binomial complexity of an infinite word $x$ maps an integer $n$ to the number of $m$-binomial equivalence classes of factors of length $n$ occurring in $x$. We study the first properties of $m$-binomial equivalence. We compute the $m$-binomial complexity of two classes of words: Sturmian words and (pure) morphic words that are fixed points of Parikh-constant morphisms like the Thue--Morse word, i.e., images by the morphism of all the letters have the same Parikh vector. We prove that the frequency of each symbol of an infinite recurrent word with bounded $2$-binomial complexity is rational. [less ▲]

Detailed reference viewed: 9 (0 ULg)
Full Text
Peer Reviewed
See detailDefining multiplication in some additive expansions of polynomial rings
Point, Françoise; Rigo, Michel ULg; Waxweiler, Laurent

in Communications in Algebra (in press)

Adapting a result of R. Villemaire on expansions of Presburger arithmetic, we show how to define multiplication in some expansions of the additive reduct of certain Euclidean rings. In particular, this ... [more ▼]

Adapting a result of R. Villemaire on expansions of Presburger arithmetic, we show how to define multiplication in some expansions of the additive reduct of certain Euclidean rings. In particular, this applies to polynomial rings over a finite field. [less ▲]

Detailed reference viewed: 7 (0 ULg)
Full Text
Peer Reviewed
See detailAn analogue of Cobham's theorem for graph directed iterated function systems
Charlier, Emilie ULg; Leroy, Julien ULg; Rigo, Michel ULg

in Advances in Mathematics (in press)

Feng and Wang showed that two homogeneous iterated function systems in $\mathbb{R}$ with multiplicatively independent contraction ratios necessarily have different attractors. In this paper, we extend ... [more ▼]

Feng and Wang showed that two homogeneous iterated function systems in $\mathbb{R}$ with multiplicatively independent contraction ratios necessarily have different attractors. In this paper, we extend this result to graph directed iterated function systems in $\mathbb{R}^n$ with contraction ratios that are of the form $\frac{1}{\beta}$, for integers $\beta$. By using a result of Boigelot {\em et al.}, this allows us to give a proof of a conjecture of Adamczewski and Bell. In doing so, we link the graph directed iterated function systems to Büchi automata. In particular, this link extends to real numbers $\beta$. We introduce a logical formalism that permits to characterize sets of $\mathbb{R}^n$ whose representations in base $\beta$ are recognized by some Büchi automata. This result depends on the algebraic properties of the base: $\beta$ being a Pisot or a Parry number. The main motivation of this work is to draw a general picture representing the different frameworks where an analogue of Cobham's theorem is known. [less ▲]

Detailed reference viewed: 18 (5 ULg)
Full Text
Peer Reviewed
See detailFish consumption patterns and hair mercury levels in children and their mothers in 17 EU countries
Castano, Argelia; Cutanda, Francisco; Esteban, Marta et al

in Environmental Research (in press)

The toxicity of methylmercury (MeHg) in humans is well established and the main source of exposure is via the consumption of large marine fish and mammals. Of particular concern are the potential ... [more ▼]

The toxicity of methylmercury (MeHg) in humans is well established and the main source of exposure is via the consumption of large marine fish and mammals. Of particular concern are the potential neurodevelopmental effects of early life exposure to low-​levels of MeHg. Therefore, it is important that pregnant women, children and women of childbearing age are, as far as possible, protected from MeHg exposure. Within the European project DEMOCOPHES, we have analyzed mercury (Hg) in hair in 1799 mother-​child pairs from 17 European countries using a strictly harmonized protocol for mercury anal. Parallel, harmonized questionnaires on dietary habits provided information on consumption patterns of fish and marine products. After hierarchical cluster anal. of consumption habits of the mother-​child pairs, the DEMOCOPHES cohort can be classified into two branches of approx. similar size: one with high fish consumption (H) and another with low consumption (L)​. All countries have representatives in both branches, but Belgium, Denmark, Spain, Portugal and Sweden have twice as many or more mother-​child pairs in H than in L. For Switzerland, Czech Republic, Hungary, Poland, Romania, Slovenia and Slovakia the situation is the opposite, with more representatives in L than H. There is a strong correlation (r=0.72) in hair mercury concn. between the mother and child in the same family, which indicates that they have a similar exposure situation. The clustering of mother-​child pairs on basis of their fish consumption revealed some interesting patterns. One is that for the same sea fish consumption, other food items of marine origin, like seafood products or shellfish contribute significantly to the mercury levels in hair. We conclude that addnl. studies are needed to assess and quantify exposure to mercury from seafood products, in particular. The cluster anal. also showed that 95​% of mothers who consume once per wk fish only, and no other marine products, have mercury levels 0.55 μg​/g. Thus, the 95th percentile of the distribution in this group is only around half the US-​EPA recommended threshold of 1 μg​/g mercury in hair. Consumption of freshwater fish played a minor role in contributing to mercury exposure in the studied cohort. The DEMOCOPHES data shows that there are significant differences in MeHg exposure across the EU and that exposure is highly correlated with consumption of fish and marine products. Fish and marine products are key components of a healthy human diet and are important both traditionally and culturally in many parts of Europe. Therefore, the communication of the potential risks of mercury exposure needs to be carefully balanced to take into account traditional and cultural values as well as the potential health benefits from fish consumption. European harmonized human biomonitoring programs provide an addnl. dimension to national HMB programs and can assist national authorities to tailor mitigation and adaptation strategies (dietary advice, risk communication, etc.) to their country's specific requirements. [less ▲]

Detailed reference viewed: 85 (10 ULg)
See detailÉclairer les enjeux de la reconstruction industrielle du bassin liégeois : l'apport des archives des Etablissements insalubres et dangereux (1919-1925)
Peters, Arnaud ULg; Defechereux, Olivier ULg; Destatte, Julien ULg

in Parmentier, Isabelle (Ed.) Actes des Deuxièmes Rencontres d'Histoire de l'Environnement en Belgique (Belgique, Luxembourg, Congo, Rwanda, Burundi) (in press)

Detailed reference viewed: 33 (16 ULg)
Full Text
Peer Reviewed
See detailA study of composite laminates failure using an anisotropic gradient-enhanced damage mean-field homogenization model
Wu, Ling ULg; Sket, Federico; Molina-Aldareguia, Jon M et al

in Composite Structures (in press)

The failure of carbon fiber reinforced epoxy laminates is studied using an anisotropic gradient-enhanced continuum damage model embedded in a mean-field homogenization scheme. In each ply, a homogenized ... [more ▼]

The failure of carbon fiber reinforced epoxy laminates is studied using an anisotropic gradient-enhanced continuum damage model embedded in a mean-field homogenization scheme. In each ply, a homogenized material law is used to capture the intra-laminar failure. The anisotropy of the homogenized material model results from the homogenization method and from the reformulation of the non-local continuum damage theory to account for the material anisotropy. As a result the damage propagation direction in each ply is predicted with accuracy as compared to the experimental results, while the problems of losing uniqueness and strain localization, which occur in classical finite element simulations when strain softening of materials is involved, can be avoided. To model the delamination process, the hybrid discontinuous Galerkin/extrinsic cohesive law method is introduced at the ply interfaces. This hybrid method avoids the need to propagate topological changes in the mesh with the propagation of the delamination while it preserves the consistency and stability in the un-cracked interfaces. As a demonstration, open-hole coupons with different stacking sequences are studied numerically and experimentally. Both the intra- and inter-laminar failure patterns are shown to be well captured by the computational framework. [less ▲]

Detailed reference viewed: 45 (12 ULg)
Full Text
Peer Reviewed
See detailUsing kernels and ecological niche modelling to delineate conservation areas in an endangered patch-breeding phenotype
Denoël, Mathieu ULg; Ficetola, Francesco

in Ecological Applications (in press)

Efficient delineation of conservation areas is a great challenge in maintaining biodiversity. Kernel density estimators (KDEs) are a powerful tool in this perspective, but they have not been applied at ... [more ▼]

Efficient delineation of conservation areas is a great challenge in maintaining biodiversity. Kernel density estimators (KDEs) are a powerful tool in this perspective, but they have not been applied at the population level on patch-distributed organisms. This would be particularly worthy for species that need broad habitats beyond those where they can be sampled; such as terrestrial lands for pond-breeding amphibians. The aim of this study was to compare different approaches for the identification of suitable areas for conservation: KDE, ecological niche modelling, and a combination of KDE and niche models. Paedomorphosis was chosen as a model system because this is an important form of intraspecific variation that is present in numerous taxa, but geographically localized within species and globally endangered. 277 ponds were sampled in one of the hotspots of paedomorphosis to determine the abundance and distribution of paedomorphs (i.e. individuals retaining gills at the adult stage) of the palmate newt (Lissotriton helveticus), with emphasis on the connections between the most valuable populations. KDEs gave insights into the surface areas required to balance the maintenance of certain number of connected ponds and the respective number of disjoint areas in which the whole population is divided. The inclusion of barriers in the models helped in accurately designing the limits of the areas to protect. Alone, habitat models were not able to successfully delineate the area to protect, but the integration between terrestrial suitable areas or barriers and KDE allowed an objective identification of areas required for conservation. Overall, the best performance was observed by the KDE integrating ecological barriers, and by the combination between KDE and niche modelling. In a broader perspective, KDEs are thus a pertinent tool in providing quantitative spatial measurements to delineate conservation areas based on patch-abundance data with a specific focus to connectivity. [less ▲]

Detailed reference viewed: 44 (12 ULg)
Full Text
Peer Reviewed
See detailMoyens et enjeux d’une approche didactique des Illuminations
Saint-Amand, Denis ULg

in Parade Sauvage (in press), 25

Detailed reference viewed: 22 (4 ULg)
Full Text
Peer Reviewed
See detailTowards a framework for assessment and management of cumulative human impacts on marine food webs
Giakoumi, Sylvaine; Halpern, Benjamin S.; Michel, Loïc ULg et al

in Conservation Biology (in press)

Effective ecosystem-based management requires understanding ecosystem responses to multiple human threats, rather than focusing on single threats. To understand ecosystem responses to anthropogenic ... [more ▼]

Effective ecosystem-based management requires understanding ecosystem responses to multiple human threats, rather than focusing on single threats. To understand ecosystem responses to anthropogenic threats holistically, it is necessary to know how threats affect different components within ecosystems and ultimately alter ecosystem functioning. We used a case study of a Mediterranean seagrass (Posidonia oceanica) food web and expert knowledge elicitation in an application of the initial steps of a framework for assessment of cumulative human impacts on food webs. We produced a conceptual seagrass food web model, determined the main trophic relationships, identified the main threats to the food web components, and assessed the components’ vulnerability to those threats. Some threats had high (e.g., coastal infrastructure) or low impacts (e.g., agricultural runoff) on all food web components, whereas others (e.g., introduced carnivores) had very different impacts on each component. Partitioning the ecosystem into its components enabled us to identify threats previously overlooked and to reevaluate the importance of threats commonly perceived as major. By incorporating this understanding of system vulnerability with data on changes in the state of each threat (e.g., decreasing domestic pollution and increasing fishing) into a food web model, managers may be better able to estimate and predict cumulative human impacts on ecosystems and to prioritize conservation actions. [less ▲]

Detailed reference viewed: 18 (5 ULg)
Full Text
Peer Reviewed
See detailLe Mur et le masque. À propos de Banksy.
Saint-Amand, Denis ULg

in MethIS : Méthodes et Interdisciplinarité en Sciences Humaines (in press)

Detailed reference viewed: 42 (8 ULg)
Full Text
Peer Reviewed
See detailA Parallel Processing Approach to Dynamic Simulations of Combined Transmission and Distribution Systems
Aristidou, Petros ULg; Van Cutsem, Thierry ULg

in International Journal of Electrical Power & Energy Systems (in press)

Simulating a power system with both transmission and distribution networks modeled in detail is a huge computational challenge. In this paper, a Schur-complement-based domain decomposition algorithm is ... [more ▼]

Simulating a power system with both transmission and distribution networks modeled in detail is a huge computational challenge. In this paper, a Schur-complement-based domain decomposition algorithm is proposed to provide accurate, detailed dynamic simulations of such systems. The simulation procedure is accelerated with the use of parallel programming techniques, taking advantage of the parallelization opportunities inherent to domain decomposition algorithms. The proposed algorithm is general, portable and scalable on inexpensive, shared-memory, multi-core machines. A large-scale test system is used for its performance evaluation. [less ▲]

Detailed reference viewed: 14 (4 ULg)
Full Text
Peer Reviewed
See detailÀ propos de l’écologie du discours heuristique
Job, Pierre ULg; Gilot, Marguerite ULg

in Actes du 4ième congrès international sur la théorie anthropologique du didactique (TAD) : Évolutions contemporaines du rapport aux mathématiques et aux autres savoirs à l'école et dans la société (in press)

Detailed reference viewed: 9 (1 ULg)
Full Text
Peer Reviewed
See detailThe EChO science case
Tinetti, Giovanna; Grodent, Denis ULg; Gérard, Jean-Claude ULg et al

in Experimental Astronomy (in press), 2015arXiv150205747T

The discovery of almost 2000 exoplanets has revealed an unexpectedly diverse planet population. Observations to date have shown that our Solar System is certainly not representative of the general ... [more ▼]

The discovery of almost 2000 exoplanets has revealed an unexpectedly diverse planet population. Observations to date have shown that our Solar System is certainly not representative of the general population of planets in our Milky Way. The key science questions that urgently need addressing are therefore: What are exoplanets made of? Why are planets as they are? What causes the exceptional diversity observed as compared to the Solar System? EChO (Exoplanet Characterisation Observatory) has been designed as a dedicated survey mission for transit and eclipse spectroscopy capable of observing a large and diverse planet sample within its four-year mission lifetime. EChO can target the atmospheres of super-Earths, Neptune-like, and Jupiter-like planets, in the very hot to temperate zones (planet temperatures of 300K-3000K) of F to M-type host stars. Over the next ten years, several new ground- and space-based transit surveys will come on-line (e.g. NGTS, CHEOPS, TESS, PLATO), which will specifically focus on finding bright, nearby systems. The current rapid rate of discovery would allow the target list to be further optimised in the years prior to EChO's launch and enable the atmospheric characterisation of hundreds of planets. Placing the satellite at L2 provides a cold and stable thermal environment, as well as a large field of regard to allow efficient time-critical observation of targets randomly distributed over the sky. A 1m class telescope is sufficiently large to achieve the necessary spectro-photometric precision. The spectral coverage (0.5-11 micron, goal 16 micron) and SNR to be achieved by EChO, thanks to its high stability and dedicated design, would enable a very accurate measurement of the atmospheric composition and structure of hundreds of exoplanets. [less ▲]

Detailed reference viewed: 9 (1 ULg)
Full Text
Peer Reviewed
See detailDerivation and Application of Sensitivities to Assess Transient Voltage Sags caused by Rotor Swings
Weckesser, Tilman; Johannsson, Hjortur; Ostergaard, Jacob et al

in International Journal of Electrical Power & Energy Systems (in press)

The paper introduces an approach to investigate voltage sags, which are caused by large generator rotor swings following a transient disturbance. Therefore, the method exploits sensitivities derived from ... [more ▼]

The paper introduces an approach to investigate voltage sags, which are caused by large generator rotor swings following a transient disturbance. Therefore, the method exploits sensitivities derived from the algebraic network equations. These provide information on the impact of a generator on the voltage magnitude at a load bus and the e ffect of load variation on the generator's power injection. It is shown that these sensitivities give valuable information to identify critical generator-load pairs and locations for applying preventive control measures. [less ▲]

Detailed reference viewed: 19 (0 ULg)
See detailInventer. Le jeune Descartes et les voies de l’inventio en 1619-1620
Dubouclez, Olivier ULg

in Savini, Massimiliano (Ed.) Les écrits de jeunesse de Descartes (in press)

Detailed reference viewed: 14 (2 ULg)
Full Text
Peer Reviewed
See detailImaginer-lire le Capital
Pieron, Julien ULg

in Cahiers d'Etudes Germaniques (in press)

Detailed reference viewed: 11 (0 ULg)