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Peer Reviewed
See detailOn the characterization of some terpenes from Renealmia alpinia Rott. (Maas) oleoresin.
Lognay, Georges ULg; Marlier, M.; Severin, M. et al

in Flavour and Fragrance Journal (1991), 6(1),

Detailed reference viewed: 22 (2 ULg)
Peer Reviewed
See detailOn the charge transfer pathway in the Merocyanine 540 triplet state quenching by nitroxyl radical
Hoebeke, Maryse ULg; Van de Vorst, A.

in Photochemistry & Photobiology (1995), 61

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See detailOn the circular polarisation of light from axion-photon mixing
Payez, Alexandre ULg; Cudell, Jean-René ULg; Hutsemekers, Damien ULg

in Alimi, Jean-Michel; Füzfa, André (Eds.) INVISIBLE UNIVERSE: Proceedings of the Conference. AIP Conference Proceedings 1241. (2010)

From the analysis of measurements of the linear polarisation of visible light coming from quasars, the existence of large-scale coherent orientations of quasar polarisation vectors in some regions of the ... [more ▼]

From the analysis of measurements of the linear polarisation of visible light coming from quasars, the existence of large-scale coherent orientations of quasar polarisation vectors in some regions of the sky has been reported. Here, we show that this can be explained by the mixing of the incoming photons with nearly massless pseudoscalar (axion-like) particles in extragalactic magnetic fields. We present a new treatment in terms of wave packets and discuss its implications for the circular polarisation. [less ▲]

Detailed reference viewed: 34 (17 ULg)
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See detailOn the Classification of Leptons
Renson, Pierre ULg

in Physica (1961), 27

The formulae giving the electric charge and the neutrinonic charge in terms of T3 and S are generalized in order to apply them to leptons. There remains an unknown parameter. For a particular value of ... [more ▼]

The formulae giving the electric charge and the neutrinonic charge in terms of T3 and S are generalized in order to apply them to leptons. There remains an unknown parameter. For a particular value of this parameter these formulae assume the particularly symmetric forms (15) and (16). Values for S, T and T3 are assigned to the different leptons. At the time this investigation was carried out the following difficulty arose: in addition to the known leptons (neutrino, electron and muon) there remained a vacancy for an undisovered lepton, which, with regard to the charges, is similar to the neutrino. Yet this has no longer to be considered as a difficulty but well as a prediction of the theory since one was recently led to admit the existence of two neutral leptons instead of one, namely the neutrino. [less ▲]

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See detailOn the co-existence of chemically peculiar Bp stars, slowly pulsating B stars and constant B stars in the same part of the HR diagram
Briquet, Maryline ULg; Hubrig, S.; De Cat, P. et al

in Astronomy and Astrophysics (2007), 466

Aims: In order to better model massive B-type stars, we need to understand the physical processes taking place in slowly pulsating B (SPB) stars, chemically peculiar Bp stars, and non-pulsating normal B ... [more ▼]

Aims: In order to better model massive B-type stars, we need to understand the physical processes taking place in slowly pulsating B (SPB) stars, chemically peculiar Bp stars, and non-pulsating normal B stars co-existing in the same part of the H-R diagram. <BR />Methods: We carry out a comparative study between samples of confirmed and well-studied SPB stars and a sample of well-studied Bp stars with known periods and magnetic field strengths. We determine their evolutionary state using accurate HIPPARCOS parallaxes and Geneva photometry. We discuss the occurrence and strengths of magnetic fields as well as the occurrence of stellar pulsation among both groups. Further, we make a comparison of Geneva photometric variability for both kinds of stars. <BR />Results: The group of Bp stars is significantly younger than the group of SPB stars. Longitudinal magnetic fields in SPB stars are weaker than those of Bp stars, suggesting that the magnetic field strength is an important factor for B type stars to become chemically peculiar. The strongest magnetic fields appear in young Bp stars, indicating a magnetic field decay in stars at advanced ages. Rotation periods of Bp and pulsation periods of SPB stars are of the same order and the behaviour of Geneva photometric variability of some Bp stars cannot be distinguished from the variability of SPB stars, illustrating the difficulty to interpret the observed variability of the order of days for B-type stars. We consider the possibility that pulsation could be responsible for the variability among chemically peculiar stars. In particular, we show that a non-linear pulsation model is not excluded by photometry for the Bp star HD 175362. [less ▲]

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See detailOn the coherent drag-reducing and turbulence-enhancing behaviour of polymers in wall flows
Dubief, Yves; White, Christopher M.; Terrapon, Vincent ULg et al

in Journal of Fluid Mechanics (2004), 514

Numerical simulations of turbulent polymer solutions using the FENE-P model are used to characterize the action of polymers on turbulence in drag-reduced flows. The energetics of turbulence is ... [more ▼]

Numerical simulations of turbulent polymer solutions using the FENE-P model are used to characterize the action of polymers on turbulence in drag-reduced flows. The energetics of turbulence is investigated by correlating the work done by polymers on the flow with turbulent structures. Polymers are found to store and to release energy to the flow in a well-organized manner. The storage of energy occurs around near-wall vortices as has been anticipated for a long time. Quite unexpectedly, coherent release of energy is observed in the very near-wall region. Large fluctuations of polymer work are shown to re-energize decaying streamwise velocity fluctuations in highspeed streaks just above the viscous sublayer. These distinct behaviours are used to propose an autonomous regeneration cycle of polymer wall turbulence, in the spirit of Jimenez & Pinelli (1999). [less ▲]

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See detailOn the collapse behaviour of oil reservoir chalk
De Gennaro, Vincenzo; Delage, Pierre; Priol, Grégoire et al

in Geotechnique (2004), 54(6), 415-420

Oil exploitation in North Sea Ekofisk oilfield started in 1971, the reservoir is located in a 150 m thick layer of porous chalk (n = 40-50%) at a 3000 m depth. Enhanced oil recovery procedure by sea water ... [more ▼]

Oil exploitation in North Sea Ekofisk oilfield started in 1971, the reservoir is located in a 150 m thick layer of porous chalk (n = 40-50%) at a 3000 m depth. Enhanced oil recovery procedure by sea water injection (waterflooding) was initiated in 1987. Starting from this date, seabed subsidence due to chalk compaction evolves at a fairly constant rate (i.e. 40 cm/year). Nowadays, the decrease of the seafloor level is of about 10 m. Reservoir management and production strategies are at the origin of the growing interest of petroleum industry in disposing of a comprehensive description of the chalk mechanical behaviour. In this note the subsidence due to waterflooding is interpreted within a framework taken from the mechanics of unsaturated soils. By considering oil as the non-wetting fluid and water as the wetting fluid, chalk compaction is depicted as a collapse phenomenon due to oil-water suction decrease. A series of suction controlled tests in the osmotic oedometer cell are presented. Water weakening effects and chalk compaction (collapse) seem likely to occur through the lost of strength of the inter-granular links existing in the oil saturated sample. The nature of these links includes both capillary and physico-chemical fluids-chalk interactions, and is well characterised by the oil-water suction. [less ▲]

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See detailOn the combination of corpus-based and experimental methodologies in the study of causal, contrastive and metadiscourse connectives in L1 and L2 text comprehension and production
Perrez, Julien ULg; Degand, Liesbeth

in Archer, Dawn; Rayson, Paul; Wilson, Andrew (Eds.) et al Proceedings of the Corpus Linguistics 2003 Conference (2003)

Detailed reference viewed: 14 (1 ULg)
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See detailOn the complementarity of contrastive linguistics and interlanguage studies
Rasier, Laurent ULg; Hiligsmann, Philippe

Conference (2008)

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See detailOn the concept of exposure time
Delhez, Eric ULg

in Continental Shelf Research (2013), 71

The concept of exposure time offers an interesting alternative to the residence time for the quantitative assessment of the water renewal of estuaries and semi-enclosed basins. It can cope with the ... [more ▼]

The concept of exposure time offers an interesting alternative to the residence time for the quantitative assessment of the water renewal of estuaries and semi-enclosed basins. It can cope with the oscillations or meandering of the flow around the boundary of the control domain and is therefore particularly suited for tidal seas and sub-basins with strong mesoscale activity. We show however that the exposure time in a control domain \omega cannot be properly defined if \omega is part of a larger bounded system unless some removal process is taken into account. It is therefore suggested to revise and extend the definition of the exposure time by including a first order decay : ``the exposure time for the rate constant \lambda is the total time spent in a control domain \omega by particles subject to a first order decay with a rate constant $\lambda$, irrespective of their possible excursions in and out the control domain''. The exposure time revised in this way is well-defined in all circumstances provided that the decay rate differs from zero but depends on the rate constant \lambda. Alternatively, in order to diagnose the movement of water masses, the first order decay can be considered only outside the control domain. [less ▲]

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See detailOn the concrete complexity of the successor function
Berthé, Valérie; Frougny, Christiane; Rigo, Michel ULg et al

Conference (2012, September 11)

We consider two kinds of questions about the successor function. The first one is concerned with the estimation of the length of the carry propagation when applying the successor map on the first n ... [more ▼]

We consider two kinds of questions about the successor function. The first one is concerned with the estimation of the length of the carry propagation when applying the successor map on the first n integers (or more generally on the first n elements in a given language). This leads to the notion of amortized (or average) carry propagation when applying the successor function. The second question is a computational issue: estimating the number of operations (in classical terms of Turing machines complexity) required to compute the representations of the first n integers from the first one by applying n times the successor function. This leads to the notion of (amortized) complexity, i.e., the average amount of computations required to obtain the successor of an element. [less ▲]

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See detailOn the constitutive equations of the chalk
Charlier, Robert ULg; Radu, Jean-Pol ULg

in ICONMIG'88 (1988)

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See detailOn the construction of automata from linear arithmetic constraints
Wolper, Pierre ULg; Boigelot, Bernard ULg

in Lecture Notes in Computer Science (2000, March), 1785

This paper presents an overview of algorithms for constructing automata from linear arithmetic constraints. It identifies one case in which the special structure of the automata that are constructed ... [more ▼]

This paper presents an overview of algorithms for constructing automata from linear arithmetic constraints. It identifies one case in which the special structure of the automata that are constructed allows a linear-time determinization procedure to be used. Furthermore, it shows through theoretical analysis and experiments that the special structure of the constructed automata does, in quite a general way, render the usual upper bounds on automata operations vastly overpessimistic. [less ▲]

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See detailOn the construction of the inclusion boundary neighbourhood for markov equivalence classes of bayesian network structures
Auvray, Vincent; Wehenkel, Louis ULg

in Proceedings of Uncertainty in Artificial Intelligence (2002)

The problem of learning Markov equivalence classes of Bayesian network structures may be solved by searching for the maximum of a scoring metric in a space of these classes. This paper deals with the ... [more ▼]

The problem of learning Markov equivalence classes of Bayesian network structures may be solved by searching for the maximum of a scoring metric in a space of these classes. This paper deals with the definition and analysis of one such search space. We use a theoretically motivated neighbourhood, the inclusion boundary, and represent equivalence classes by essential graphs. We show that this search space is connected and that the score of the neighbours can be evaluated incrementally. We devise a practical way of building this neighbourhood for an essential graph that is purely graphical and does not explicitely refer to the underlying independences. We find that its size can be intractable, depending on the complexity of the essential graph of the equivalence class. The emphasis is put on the potential use of this space with greedy hillclimbing search. [less ▲]

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See detailOn the Construction of WiMAX Mesh Tree
Nahle, Salim; Iannone, Luigi,; Donnet, Benoît ULg et al

in IEEE Communications Letters (2007), 11(12),

The IEEE 802.16 protocol, also known as WiMAX, has been designed to support long-range communications with high bitrates, using two operation modes: Point-to-Multi-Point (PMP) and Mesh. In the mesh mode ... [more ▼]

The IEEE 802.16 protocol, also known as WiMAX, has been designed to support long-range communications with high bitrates, using two operation modes: Point-to-Multi-Point (PMP) and Mesh. In the mesh mode, Subscriber Stations (SSs) can directly communicate with each other, thus forming a tree, and can be used to forward other's data packets in a multi-hop fashion. On the contrary, in the PMP mode only one hop communication toward the Base Station (BS) is allowed. In this paper, we investigate the performance of the mesh mode by proposing an algorithm for constructing the WiMAX mesh tree. Our algorithm increases routes' effective throughput by splitting long links into multiple shorter ones. We show through simulations that this approach leads to improving the throughput capacity of WiMAX-based wireless mesh networks. [less ▲]

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See detailOn the convergence of relaxation schemes to couple phasor-mode and electromagnetic transients simulations
Plumier, Frédéric ULg; Geuzaine, Christophe ULg; Van Cutsem, Thierry ULg

in Proceedings of the IEEE PES General Meeting (2014, July)

Hybrid simulations combining phasor-mode and electromagnetic transients models aim at taking advantage of computational speed of the former and accuracy of the latter. For simulation accuracy, a ... [more ▼]

Hybrid simulations combining phasor-mode and electromagnetic transients models aim at taking advantage of computational speed of the former and accuracy of the latter. For simulation accuracy, a relaxation process is used, which consists of iterating between both models. The convergence properties of this relaxation process are investigated. The speed of convergence is assessed when the variables exchanged at the interface between both models are respectively pure voltage/current sources, Norton/Thévenin equivalents, or a combination of them. Iteratively updated Norton/Thévenin equivalents are shown to drastically reduce the number of relaxation iterations. [less ▲]

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See detailOn the Convergence of Social Protection Performance in the European Union
Lefebvre, Mathieu ULg

Scientific conference (2010, May)

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See detailOn the Convergence of Social Protection Performance in the European Union
Lefebvre, Mathieu ULg; Coelli, Tim; Pestieau, Pierre ULg

in CESifo Economic Studies (2010), 56(2), 300-322

In this article, we use data on five social inclusion indicators (poverty, inequality, unemployment, <br />education and health) to assess and compare the performance of 15 European <br />welfare states ... [more ▼]

In this article, we use data on five social inclusion indicators (poverty, inequality, unemployment, <br />education and health) to assess and compare the performance of 15 European <br />welfare states (EU15) over a 12-year period from 1995 to 2006. Aggregate measures of <br />performance are obtained using index number methods similar to those employed in the <br />construction of the widely used Human Development Index. These are compared with <br />alternative measures derived from data envelopment analysis methods. The influence of <br />methodology choice and the assumptions made in scaling indicators upon the results <br />obtained is illustrated and discussed. We then analyse the evolution of performance <br />over time, finding evidence of some convergence in performance and no sign of social <br />dumping. [less ▲]

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See detailOn the correlation between oxygen uptake in plastids of greening etiolated oat leaves and pigment photooxidation
Franck, Fabrice ULg; Schmid, G. H.

in Zeitschrift für Naturforschung. Section C : Biosciences (1985), 40c

Detailed reference viewed: 9 (4 ULg)