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See detailOn the detection of influential subsets of categories in goodness of fit testing
Magis, David ULg

Conference (2005, August)

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See detailOn the detection of influential subsets of categories in goodness of fit testing
Magis, David ULg

in Statistical Methodology (2007), 4

In this paper we focus on the well-known test of goodness of fit for comparing observed counts to expected values under some null hypothesis. When the latter is rejected, we propose a simple method for ... [more ▼]

In this paper we focus on the well-known test of goodness of fit for comparing observed counts to expected values under some null hypothesis. When the latter is rejected, we propose a simple method for detecting which subset(s) of category counts provoke(s) that rejection. The approach aims at building intervals iteratively and drawing appropriate conclusions on that basis.We discuss this method with respect to other classical approaches. We illustrate our purpose by treating some examples. [less ▲]

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See detailOn the determination of local buckling modes for the design of thin walled members
Rossi, Barbara ULg; Rondal, Jacques ULg

in International Conference on Coupled instabilities in metal structures: CIMS2004, Rome 27-29 September 2004 (2004)

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See detailOn the determination of oxygen abundances in chromospherically active stars
Morel, Thierry ULg; Micela, G.

in Astronomy and Astrophysics (2004), 423

We discuss oxygen abundances derived from [O I] λ6300s and the O I triplet in stars spanning a wide range in chromospheric activity level, and show that these two indicators yield increasingly discrepant ... [more ▼]

We discuss oxygen abundances derived from [O I] λ6300s and the O I triplet in stars spanning a wide range in chromospheric activity level, and show that these two indicators yield increasingly discrepant results with higher chromospheric/coronal activity measures. While the forbidden and permitted lines give fairly consistent results for solar-type disk dwarfs, spuriously high O I triplet abundances are observed in young Hyades and Pleiades stars, as well as in individual components of RS CVn binaries (up to 1.8 dex). The distinct behaviour of the [O I]-based abundances which consistently remain near-solar suggests that this phenomenon mostly results from large departures from LTE affecting the O I triplet at high activity level that are currently unaccounted for, but also possibly from a failure to adequately model the atmospheres of K-type stars. These results suggest that some caution should be exercised when interpreting oxygen abundances in active binaries or young open cluster stars. Based on observations collected at the European Southern Observatory, Chile (Proposals 64.L-0249 and 071.D-0260). Table \ref{tab_data} is only available in electronic form at http://www.edpsciences.org [less ▲]

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See detailOn the development of a model updating strategy of nonlinear vibrating structures
Kerschen, Gaëtan ULg; Golinval, Jean-Claude ULg

in ASME International Design Engineering Technical Conferences, Chicago, 2003 (2003, September)

The objective of this paper is to present a model updating strategy of non-linear vibrating structures. Because modal analysis is no longer helpful in non-linear structural dynamics, a special attention ... [more ▼]

The objective of this paper is to present a model updating strategy of non-linear vibrating structures. Because modal analysis is no longer helpful in non-linear structural dynamics, a special attention is devoted to the features extracted from the proper orthogonal decomposition and one of its non-linear generalisations based on auto-associative neural networks. The efficiency of the proposed procedure is illustrated using simulated data from a three-dimensional portal frame. [less ▲]

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See detailOn the development of an integrated bone remodeling law for orthodontic tooth movements models using the Finite Element Method.
Mengoni, Marlène ULg

Doctoral thesis (2012)

One of the guiding principles in orthodontics is to gradually impose progressive and irreversible bone deformations due to remodeling using specific force systems on the teeth. Bone remodeling leads the ... [more ▼]

One of the guiding principles in orthodontics is to gradually impose progressive and irreversible bone deformations due to remodeling using specific force systems on the teeth. Bone remodeling leads the teeth into new positions with two tissues having a major influence: the periodontal ligament and the alveolar bone. Their mechanical and biological/physiological reactions to orthodontic forces are tightly linked. This mechanical biological coupling can be treated in biomechanical models, focusing on the mechanics and considering the phenomenological aspects of the biology/physiology. The development of such a model for bone tissue within a Finite Element framework is the core of this work. We propose to reconcile two approaches of bone modeling (small strains linear elasticity for remodeling problems and complex constitutive models for other applications) by writing a constitutive model for trabecular bone at macroscopic level, built on morphological parameters to describe the anisotropy, and accounting for effects such as plasticity of the trabeculae. The continuum parameters such as the stiffness can evolve with morphology as remodeling occurs in the tissue. For this, we extend and enhance Doblaré and Garcia's remodeling phenomenological model. The remodeling process corresponds to an evolution of a damage tensor representing the bone morphology. To do so, we propose an integration method for an anisotropic Continuum Damage model coupled to plasticity. Adapting Doblaré and Garcia's remodeling law to our constitutive model, we extend it so that it can be used in the specific case of orthodontic tooth movement, still following Frost's mechanostat theory. We propose to include the hydrostatic pressure dependency of remodeling, due to the presence of the periodontal ligament, within the bone remodeling law. We finally present a validation method for the mechanical representation of the bone matrix through the knowledge of its morphology, both on engineered cellular solids with bone-like morphology (aluminum and polymeric foams) and on bone (Deer antler) samples. Applying the model on the benchmark problem of the proximal femur remodeling, leads to results that are comparable to other models of the literature. We can therefore assume the way the remodeling model is built is valid. We finally apply the developed model to orthodontic tooth movement simulations. First we propose a model accounting for the non-linear mechanical response of the PdL through either bilateral contact conditions or spring models. We then present applications of orthodontic tooth movement, either displacement driven or force driven, both 2D and 3D. We thus show we can qualitatively represent the tooth movement, however outlining some of the drawbacks of the models (an unphysiological density distribution can arise due to the poor representation of the actual loads and a strong dependence on the boundary conditions is pointed out). However, we can represent the formation and resorption of hyaline areas, the non-linearity of the force/displacement relationship, and that applying a stepwise increasing force leads to higher displacements than a high initial force as there is no hyaline zone to resorb. [less ▲]

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See detailOn the dichotomic collective behaviors of large populations of pulse-coupled firing oscillators
Mauroy, Alexandre ULg

Doctoral thesis (2011)

The study of populations of pulse-coupled firing oscillators is a general and simple paradigm to investigate a wealth of natural phenomena, including the collective behaviors of neurons, the ... [more ▼]

The study of populations of pulse-coupled firing oscillators is a general and simple paradigm to investigate a wealth of natural phenomena, including the collective behaviors of neurons, the synchronization of cardiac pacemaker cells, or the dynamics of earthquakes. In this framework, the oscillators of the network interact through an instantaneous impulsive coupling: whenever an oscillator fires, it sends out a pulse which instantaneously increments the state of the other oscillators by a constant value. There is an extensive literature on the subject, which investigates various model extensions, but only in the case of leaky integrate-and-fire oscillators. In contrast, the present dissertation addresses the study of other integrate-and-fire dynamics: general monotone integrate-and-fire dynamics and quadratic integrate-and-fire dynamics. The main contribution of the thesis highlights that the populations of oscillators exhibit a dichotomic collective behavior: either the oscillators achieve perfect synchrony (slow firing frequency) or the oscillators converge toward a phase-locked clustering configuration (fast firing frequency). The dichotomic behavior is established both for finite and infinite populations of oscillators, drawing a strong parallel between discrete-time systems in finite-dimensional spaces and continuous-time systems in infinite-dimensional spaces. The first part of the dissertation is dedicated to the study of monotone integrate-and-fire dynamics. We show that the dichotomic behavior of the oscillators results from the monotonicity property of the dynamics: the monotonicity property induces a global contraction property of the network, that forces the dichotomic behavior. Interestingly, the analysis emphasizes that the contraction property is captured through a 1-norm, instead of a (more common) quadratic norm. In the second part of the dissertation, we investigate the collective behavior of quadratic integrate-and-fire oscillators. Although the dynamics is not monotone, an “average” monotonicity property ensures that the collective behavior is still dichotomic. However, a global analysis of the dichotomic behavior is elusive and leads to a standing conjecture. A local stability analysis circumvents this issue and proves the dichotomic behavior in particular situations (small networks, weak coupling, etc.). Surprisingly, the local stability analysis shows that specific integrate-and-fire oscillators exhibit a non-dichotomic behavior, thereby suggesting that the dichotomic behavior is not a general feature of every network of pulse-coupled oscillators. The present thesis investigates the remarkable dichotomic behavior that emerges from networks of pulse-coupled integrate-and-fire oscillators, putting emphasis on the stability properties of these particular networks and developing theoretical results for the analysis of the corresponding dynamical systems. [less ▲]

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See detailOn the difficulty of relational concepts among participants with Down syndrome
Facon, Bruno; Magis, David ULg; Courbois, Yannick

in Research in Developmental Disabilities (2012), 33

The aim of the study was to compare the difficulty of relational concepts among participants with and without intellectual disability. The French versions of the Boehm Tests of Basic Concepts Third ... [more ▼]

The aim of the study was to compare the difficulty of relational concepts among participants with and without intellectual disability. The French versions of the Boehm Tests of Basic Concepts Third Edition (Preschool and Kindergarten to 2nd grade) were administered to three groups of 47 participants individually matched on their total raw score on the tests. The first group comprised participants with intellectual disability of undifferentiated etiology, the second, participants with Down syndrome and the third, typical children. Item analyses using the transformed item difficulties method to detect differential item functioning across groups showed that the groups' rank-orders of item difficulty were highly similar. It is concluded that, all things being equal, relational concepts are of comparable difficulty and follow a similar sequence of development whatever the cognitive and etiological status of participants. Methodological and theoretical implications of these findings are discussed. [less ▲]

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See detailOn the distribution of the absorbing atoms in the reversing layers of stars and the formation of blended absorption lines
Swings, Polydore ULg; Chandrasekhar, S.

in Monthly Notices of the Royal Astronomical Society (1936), 97(1), 24-37

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See detailOn the dynamic stability of Saturn's F ring
Poulet, F.; Jancart, Sylvie ULg

in Bulletin of the American Astronomical Society (2000, May 01)

We explore the dynamics of Saturn's F ring by following the orbital histories of circumplanetary particles between the orbits of Prometheus and Pandora. Our goal is to find structures that could be ... [more ▼]

We explore the dynamics of Saturn's F ring by following the orbital histories of circumplanetary particles between the orbits of Prometheus and Pandora. Our goal is to find structures that could be related to the F ring. Using a 3-D mapping integrator developped by Sicardy and Foryta (1996), we follow the behavior of several thousand test particles distributed unformly between 140,000 and 140,400 km in order to acquire a general picture of the dynamics of this zone. The model includes the gravitational effects of Saturn (up to J[SUB]4[/SUB]) and the two shepherd satellites. The numerical simulations show chaotic behaviors of the particles resulting in a close encounter with one or the other of the satellites, which deplete the zone between the satellites. The timescale over which particles are removed by the satellites is of order a ten thousand years. After a hundred thousand years, some particles exist but they are not related to the actual four strands of the F ring. As suggested by Cuzzi and Burns (1988), these simulations indicate that this ring may be a transient event occuring at the edge of the Roche limit. However, taking into account dissipation (collisions, viscosity) might help to explain the longevity and the location of this ring. This work was performed while the author held a National Research Council - NASA ARC Research Associateship. [less ▲]

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See detailOn the Dynamics of Locators in LISP
Saucez, Damien; Donnet, Benoît ULg

in IFIP/TC6 Networking (2012, May)

In the Internet, IP addresses play the dual role of identifying the hosts and locating them on the topology. This design choice limits the way a network can control its traffic and causes scalability ... [more ▼]

In the Internet, IP addresses play the dual role of identifying the hosts and locating them on the topology. This design choice limits the way a network can control its traffic and causes scalability issues. To overcome this limitation, the Locator/Identifier Separation Protocol (LISP) has been introduced. In LISP, the addresses used to identify end hosts (i.e., identifiers) are independent of the addresses used to locate them (i.e., locators). LISP maps identifiers into a list of locators and provides a mean to transport the packets with the appropriate locator. A key feature of this separation is that several locators can be associated to a given identifier, leading to more control for an end-site on the path selection to reach a given destination. In this paper, we show that the choice of the locator can have an impact on the performance and the reliability of the communication in a LISP environment. To this aim, we build a mapping between identifiers and locators as if LISP were deployed today. In addition, we extensively collect delay data between locators and demonstrate that the locator selection for a given identifier prefix impacts the performance of the LISP path in 25% of the cases. Finally, we measure the locators availability over time and demonstrate that it remains quite stable. [less ▲]

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See detailOn the Edge of Genre: The Prose Poem and the Short Short Story
Delville, Michel ULg

in Pagnoulle, Christine (Ed.) Writing (On) Short Stories (1997)

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See detailOn the effect of concrete surface roughness on stress wave propagation in repair systems
Piotrowski, T.; Garbacz, A.; Schwall, D. et al

in Adhesion in Interfaces of Building Materials: a Multi-Scale Approach (2007)

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See detailOn the effects of inhomogeneities in high excitation H II regions
Manfroid, Jean ULg

in Astrophysics & Space Science (1978), 53

The hypothesis that observations of inhomogeneities in H II regions would be changed by adopting a filling factor other than one is investigated by comparing models of H II regions with filling factors of ... [more ▼]

The hypothesis that observations of inhomogeneities in H II regions would be changed by adopting a filling factor other than one is investigated by comparing models of H II regions with filling factors of one and one eighth. Attention is given to conditions when the hydrogen and helium fronts are close together, i.e. high excitation H II regions. Results obtained through use of an iterative scheme, whereby the nebula is divided into concentric shells with variable thickness, indicate that some emission lines, e.g., O II, S II, S III, N II, are substantially altered when the filling factor is smaller than one [less ▲]

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See detailOn the electrochemical polymerization of acrylonitrile and N-vinylpyrrolidone : new insight into the mechanism
Jérôme, Robert ULg; Mertens, Marc; Martinot, Lucien

in Advanced Materials (1995), 7(9), 807-809

The protection of metals against environmental attack can be achieved by coating the metal with a protective organic film. Poor adhesion of the organic film to the metal surface has, however, limited the ... [more ▼]

The protection of metals against environmental attack can be achieved by coating the metal with a protective organic film. Poor adhesion of the organic film to the metal surface has, however, limited the success of this approach. Here it is demonstrated that polyacrylonitride can be elecrografted onto a nickel surface producing a strongly adherent film. The transformation of the organic film could also open the way to new polymer-metal composites. [less ▲]

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See detailOn the embryonic form of Nematobothrium filarina
Van Beneden, Édouard ULg

in Quarterly Journal of Microscopical Science (The) (1870), 2(10), 136-143

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See detailOn the emission lines in the spectrum of BD +20° 2465
Swings, Polydore ULg; Struve, Otto

in Publications of the Astronomical Society of the Pacific [=PASP] (1941), 53

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See detailOn the Emission Spectrum of Orion
Manfroid, Jean ULg

in Astronomy and Astrophysics (1977), 57

Abstract image available at: http://cdsads.u-strasbg.fr/abs/1977A&A....57..303M

Detailed reference viewed: 5 (0 ULg)