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See detailWavelet series representations for pathwise Young integrals
Esser, Céline ULiege

Conference (2016, October)

Detailed reference viewed: 14 (2 ULiège)
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See detailWavelet Spectrum Estimation under Chronology Uncertainties Application to Dust Flux Data from Belgian Fagnes
Lenoir, Guillaume; Allan, Mohammed ULiege; Crucifix, Michel et al

Poster (2012, July)

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See detailA wavelet-based analysis of surface air temperature regularity
Deliège, Adrien ULiege; Nicolay, Samuel ULiege

Conference (2014, June 19)

The aim of the talk is to present the "wavelet transform microscope" and the wavelet leaders method to show that surface air temperature signals of weather stations selected in Europe are monofractal, i.e ... [more ▼]

The aim of the talk is to present the "wavelet transform microscope" and the wavelet leaders method to show that surface air temperature signals of weather stations selected in Europe are monofractal, i.e. all the points have the same Hölder (regularity) exponent. This study reveals that the information obtained in this way are richer than previous works studying long range correlations in meteorological stations. The approach presented here allows to bind the Hölder exponents with the pressure anomalies, and such a link does not exist with methods previously carried out. Moreover, this regularity is a signature of the type of climate the stations are associated to: indeed, it is possible to establish a climate classification of weather stations in Europe which matches the Köppen-Geiger climate classification. A blind test is performed in order to confirm the results, which can be partly explained by the influence of the North Atlantic Oscillation. This result could give rise to new criteria to determine the efficiency of current climatic models. [less ▲]

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See detailA wavelet-based analysis of surface air temperature variability
Deliège, Adrien ULiege; Nicolay, Samuel ULiege

Conference (2014, June 06)

We study the Hölder regularity of surface air temperature signals using the wavelet leaders method (WLM). This method has been successfully applied in several domains such as DNA analysis, fully ... [more ▼]

We study the Hölder regularity of surface air temperature signals using the wavelet leaders method (WLM). This method has been successfully applied in several domains such as DNA analysis, fully developped turbulence analysis, internet data traffic analysis,... to name just a few, and we now use it in climatology. We first define the notions of Hölder exponent, monofractal functions and spectrum of singularities before explaining the WLM. Then we use it to study surface air temperature signals from weather stations spread across Western and Eastern Europe and show that they are monofractal, i.e. their irregularity (in the sense of variability) is regular. After, we show that the stations can be classified according to their Hölder exponent and that this classification matches with the worldwide used Köppen-Geiger climate classification. A blind test is performed in order to confirm the results, which can be partly explained by the influence of the North Atlantic Oscillation. Our results can be helpful to test the accuracy of current climatic models. [less ▲]

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See detailWavelet-based method to disentangle transcription-and replication-associated strand asymmetries in mammalian genomes
Baker, A.; Nicolay, Samuel ULiege; Zaghloul, L. et al

in Applied & Computational Harmonic Analysis (2010), 28

During genome evolution, the two strands of the DNA double helix are not subjected to the same mutation patterns. This mutation bias is considered as a by-product of replicative and transcriptional ... [more ▼]

During genome evolution, the two strands of the DNA double helix are not subjected to the same mutation patterns. This mutation bias is considered as a by-product of replicative and transcriptional activities. In this paper, we develop a wavelet-based methodology to analyze the DNA strand asymmetry profiles with the specific goal to extract the contributions associated with replication and transcription respectively. In a first step, we use an adapted N-shaped analyzing wavelet to perform a multi-scale pattern recognition analysis of the sum of the TA and GC skews along human chromosomes. This method provides an 1 Mbp characteristic objective segmentation of the human genome in skew domains of size, bordered by two putative replication origins recognized as large amplitude upward jumps in the noisy skew profile. In a second step, we use a least-square fitting procedure to disentangle, in these skew domains, the small-scale (the mean human gene size 30 kbp) square-like transcription component from the global N-shaped component induced by replication. When applying this procedure to the 22 human autosomes, we delineate 678 replication domains of mean length L = 1.2 ± 0.6 Mbp spanning 33.8% of the human genome and we predict 1062 replication origins. When investigating the distribution of transcription-associated skew inside the replication N-domains, we reveal some dependence upon the distance to the putative replication origins located at N- domain extremities, the closer the genes to the origin, the larger their transcription bias as the signature of a higher transcriptional activity in the germ-line. As a comparative analysis, we further apply our wavelet-based methodology to skew profiles along the mouse chromosomes. The striking similarity of the results in human and mouse indicates that the remarkable gene organization observed inside the human replication N-domains is likely to be a general feature of mammalian genomes. [less ▲]

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See detailWavelet-based Methods to Study the Regularity of a Signal: from Theory to Practice
Kleyntssens, Thomas ULiege; Nicolay, Samuel ULiege

Conference (2016, March 23)

In this talk, I use the notion of wavelet to design multifractal formalisms. I present the theoritical results obtained on the generalized Snu spaces and I show the utility of these generalization ... [more ▼]

In this talk, I use the notion of wavelet to design multifractal formalisms. I present the theoritical results obtained on the generalized Snu spaces and I show the utility of these generalization. Besides, I also apply these formalisms on a practical example: the Mars topography. [less ▲]

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See detailA wavelet-based mode decomposition compared to the EMD
Deliège, Adrien ULiege; Nicolay, Samuel ULiege

Poster (2015, September 08)

We introduce a new method based on wavelets for decomposing a signal into quasi-periodic oscillating components with smooth time-varying amplitudes. This method is inspired by both the "classic" wavelet ... [more ▼]

We introduce a new method based on wavelets for decomposing a signal into quasi-periodic oscillating components with smooth time-varying amplitudes. This method is inspired by both the "classic" wavelet-based decomposition and the empirical mode decomposition (EMD). We compare the efficiency of the method with the well-established EMD on toys examples and the ENSO climate index. [less ▲]

Detailed reference viewed: 98 (18 ULiège)
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See detailA wavelet-based mode decomposition
Nicolay, Samuel ULiege

in European Physical Journal B -- Condensed Matter (2011), 80

We propose a wavelet-based method for analyzing non-stationary data. The idea, inspired by the empirical mode decomposition, is to decompose a data set into a finite number of components, well separated in ... [more ▼]

We propose a wavelet-based method for analyzing non-stationary data. The idea, inspired by the empirical mode decomposition, is to decompose a data set into a finite number of components, well separated in the time-frequency plane, plus a residue, such that each component has a zero mean and is associated to one frequency only. When applied to climatic data, this method gives interesting results. [less ▲]

Detailed reference viewed: 71 (24 ULiège)
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See detailWavelets Characterization of coarsing during unstable MBE growth
Moktadir, Z; Kraft, Michael ULiege

in Proceedings of "Low Dimensional Semiconductor Devices Conference, Cancun, décembre 2004" (2004, December)

Detailed reference viewed: 20 (0 ULiège)
See detailWavelets in the forecast verification of an assimilation experiment in the Ligurian Sea
Alvera Azcarate, Aïda ULiege; Barth, Alexander ULiege; Ben Bouallegue, Z. et al

Conference (2004, June)

Detailed reference viewed: 13 (1 ULiège)
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See detailWavelets Techniques for Pointwise Anti-Hölderian Irregularity
Clausel, Marianne; Nicolay, Samuel ULiege

in Constructive Approximation (2011), 33

In this paper, we introduce a notion of weak pointwise Hölder regularity, starting from the definition of the pointwise anti-Hölder irregularity. Using this concept, a weak spectrum of singularities can ... [more ▼]

In this paper, we introduce a notion of weak pointwise Hölder regularity, starting from the definition of the pointwise anti-Hölder irregularity. Using this concept, a weak spectrum of singularities can be defined as for the usual pointwise Hölder regularity.We build a class of wavelet series satisfying the multifractal formalism and thus show the optimality of the upper bound. We also show that the weak spectrum of singularities is disconnected from the casual one (referred to here as strong spectrum of singularities) by exhibiting a multifractal function made of Davenport series whose weak spectrum differs from the strong one. [less ▲]

Detailed reference viewed: 28 (12 ULiège)
See detailWavenumbers and Oscillator Strengths for n1,3L - n'1,3L' (2 <n<50) Rydberg transitions of neutral Helium
Biémont, Emile ULiege; Quinet, Pascal ULiege

in Bulletin de la Société Royale des Sciences de Liège (1993), 62(5-6), 373-398

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See detailWaves in complex plasmas with dust distributions (charge/size/mass) revisited
Verheest, F.; Cattaert, Tom ULiege

in IEEE Transactions on Plasma Science (2004), 32(2), 653-658

Polydisperse dust, as in astrophysical observations, occurs in a range of sizes, compositions, charges, and masses, with corresponding changes to linear dispersion laws. At the fluid level the charged ... [more ▼]

Polydisperse dust, as in astrophysical observations, occurs in a range of sizes, compositions, charges, and masses, with corresponding changes to linear dispersion laws. At the fluid level the charged dust can be treated as a discrete collection of different fluids or as the continuous limit over a charge range. On the other hand, one global dust fluid needs appropriate model equations, derivable from a Klimontovich or extended Vlasov approach, in which charge, mass, and/or size enter as extra phase space variables. Due to differing charge-to-mass weightings, this is sometimes quite involved. An extended kinetic theory allows for a more correct picture, including possible microscopic damping mechanisms, but quickly becomes very unwieldy. An intermediate procedure is to use results for monodisperse dust and integrate afterwards over dust distributions. This cannot be applied blindly, so that it is necessary to check results on their applicability and consistency. Selected applications have,been treated for parallel electromagnetic, oblique electrostatic (and possibly self-gravitational), and fluid dust-Bernstein modes, to illustrate the methodological aspects of this part of dusty plasma physics. [less ▲]

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See detailThe way to agritourist development from constraints to opportunities
Dubois, Charline ULiege; Schmitz, Serge ULiege

in Cawley, Mary (Ed.) The Sustainability of Rural Systems: Local and Global Challenges and Opportunities (2011, August)

In the northwest European countryside, diversification is a common option to preserve a viable agricultural business because many farmers have to restructure their activities to face increasing pressures ... [more ▼]

In the northwest European countryside, diversification is a common option to preserve a viable agricultural business because many farmers have to restructure their activities to face increasing pressures. Many choose tourism business as a mean of diversification. To examine the supply aspect of agritourism development, the paper scrutinizes the motivations or choices reasons for farm tourism as a mean of diversification. Actually some main reasons have been underlined in the literature. Even if economic and financial reasons like new incomes and employments, stability towards agricultural market fluctuations or a better use of farm ressources are the first motivations mentioning, more social and external reasons like sharing experiences, success of other farmers, meeting of people, education of public and consummer, personal interest as a hobby are also significant. Choice reasons may change over time, be different according to the own characteristics of the farm, its development and its environment, or depend on gender. This paper uses data’s from interviews conducted in agritourism accomodations in the Walloon Region and in the Grand-Duchy of Luxembourg to explore these motivations. The research is based on a content analysis aiming a graphical representation of the motivations using an adapted actantial model: a multi-scale analysis identifying the adjuvants and constraints of such motivations is used. The first analysis stress that the answer to a market opportunity and the potential new assignement of unused farm buildings are also observed. Moreover it is showned that entrepreneurship and opportunities come as being factors quite as important as a development based on a survival of the farm. [less ▲]

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See detailA way to analyse several difficulties the pupils meet within calculus
Schneider-Gilot, Marguerite ULiege

in Proceedings 7eme congrès international sur l'enseignement des mathématiques (1992)

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See detailA Way to Deal with Model-Plant Mismatch for a Reliable Diagnosis in Transient Operation
Borguet, Sébastien ULiege; Dewallef, Pierre ULiege; Léonard, Olivier ULiege

in Proceedings of the ASME Turbo Expo 2006 (2006, May)

Least-squares health parameter identification techniques such as the Kalman filter have been massively used to solve the problem of turbine engine diagnosis. Indeed, such methods give a good estimate ... [more ▼]

Least-squares health parameter identification techniques such as the Kalman filter have been massively used to solve the problem of turbine engine diagnosis. Indeed, such methods give a good estimate provided that the discrepancies between the model prediction and the measurements are zero-mean, white random variables. In turbine engine diagnosis, however, this assumption does not always hold due to the presence of biases in the model. This is especially true for transient operation. As a result, the estimated parameters tend to diverge from their actual values which strongly deteriorates the diagnosis. The purpose of this contribution is to present a Kalman filter diagnosis tool where the model biases are treated as an additional random measurement error. The new methodology is tested on simulated transient data representative of a current turbofan layout. While relatively simple to implement, the newly developed diagnosis tool exhibits a much better accuracy than the original Kalman filter in the presence of model biases. [less ▲]

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See detailA way to deal with model-plant mismatch for a reliable diagnosis in transient operation
Borguet, Sébastien ULiege; Dewallef, Pierre ULiege; Léonard, Olivier ULiege

in Journal of Engineering for Gas Turbines & Power (2008), 130(3),

Least-squares health parameter identification techniques, such as the Kalman filter, have been extensively used to solve diagnosis problems. Indeed, such methods give a good estimate provided that the ... [more ▼]

Least-squares health parameter identification techniques, such as the Kalman filter, have been extensively used to solve diagnosis problems. Indeed, such methods give a good estimate provided that the discrepancies between the model prediction and the measurements are Zero-mean, white, Gaussian random variables. In a turbine engine diagnosis, however this assumption does not always hold due to the presence of biases in the model. This is especially true for a transient operation. As a result, the estimated parameters tend to diverge from their actual values, which strongly degrades the diagnosis. The purpose of this contribution is to present a Kalman filter diagnosis tool where the model biases are treated as an additional random measurement error. The new methodology is tested on simulated transient data representative of a current turbofan engine configuration. While relatively simple to implement, the newly developed diagnosis tool exhibits a much better accuracy than the original Kalman filter in the presence of model biases. [less ▲]

Detailed reference viewed: 55 (10 ULiège)
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See detailA way to improve management of underground utilities
Sainovic, Ivana ULiege; Billen, Roland ULiege

in De Mayer, Philippe; Neutens, Tijs; De Ryck, Marijke (Eds.) Proceedings of the 4th International Workshop on 3D Geo-Information (2009, November)

Detailed reference viewed: 85 (8 ULiège)
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See detailThe way we learn this knowledge that dominates all other knowledge
Geurten, Marie ULiege; Catale, Corinne ULiege; Meulemans, Thierry ULiege

Conference (2013)

Although much is known about how children use memory strategies, far fewer studies have examined how knowledge of those strategies improves during childhood or which variables are involved in this ... [more ▼]

Although much is known about how children use memory strategies, far fewer studies have examined how knowledge of those strategies improves during childhood or which variables are involved in this development. In this experiment, a scale designed to assess three main aspects of metamemory knowledge (internal strategy knowledge, external strategy knowledge, general knowledge) and a battery of executive tasks was administered to a group of 80 children aged 4, 6, and 11. At the same time, variables such as intelligence, vocabulary and parental education level were also taken into account. Stepwise analyses carried out on each of the three metamemory subscales showed that executive functions of inhibition and response monitoring, as well as verbal fluency, were single predictors of internal strategy knowledge for children aged 6 and 11. Only verbal fluency predicted external strategy knowledge. None of the variables included in the analyses could explain the children’s general knowledge of memory functioning or the 4-year-old group’s performance on any of the three subscales. Results are discussed in terms of ease of monitoring, access to explicit knowledge and influence of implicit learning. [less ▲]

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See detailWayemadje
Gilliard, Emile; Baiwir, Esther ULiege

Book published by Société de Langue et de Littérature Wallonnes (2013)

Detailed reference viewed: 25 (2 ULiège)