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See detailOn the existence of maximum likelihood estimates in logistic regression models
Albert, Adelin ULg; Anderson, JA.

in Biometrika (1984)

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See detailOn the exploitation of chaos to build reduced-order models
Kerschen, Gaëtan ULg; Feeny, B. F.; Golinval, Jean-Claude ULg

in Computer Methods in Applied Mechanics & Engineering (2003), 192(13-14), 1785-1795

The present study focuses on the model reduction of non-linear systems. The proper orthogonal decomposition is exploited to compute eigenmodes from time series of displacement. These eigenmodes, called ... [more ▼]

The present study focuses on the model reduction of non-linear systems. The proper orthogonal decomposition is exploited to compute eigenmodes from time series of displacement. These eigenmodes, called the proper orthogonal modes, are optimal with respect to energy content and are used to build a low-dimensional model of the non-linear system. For this purpose, the proper orthogonal modes obtained from a chaotic orbit are considered. Indeed, such an orbit is assumed to cover a portion of the phase space of higher dimension, and hence of greater measure. This higher dimensional data is further assumed to contain more information about the system dynamics than data of a lower-dimensional periodic orbit. In an example, it is shown that the modes for this particular behaviour are more representative of the system dynamics than any other set of modes extracted from a non-chaotic response. This is applied to a buckled beam with two permanent magnets and the reduced-order model is validated using both qualitative and quantitative comparisons. (C) 2003 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailOn the exploitation of chaos to build reduced-order models
Kerschen, Gaëtan ULg; Feeny, B. F.; Golinval, Jean-Claude ULg

in International Conference on Noise and Vibration Engineering, Leuven, 2002 (2002, September)

The present study focuses on the model reduction of non-linear systems. The proper orthogonal decomposition is exploited to compute eigenmodes from time series of displacement. These eigenmodes, called ... [more ▼]

The present study focuses on the model reduction of non-linear systems. The proper orthogonal decomposition is exploited to compute eigenmodes from time series of displacement. These eigenmodes, called the proper orthogonal modes, are optimal with respect to energy content and are used to build a low-dimensional model of the non-linear system. For this purpose, the proper orthogonal modes obtained from a chaotic orbit are considered. Indeed, such an orbit is assumed to cover the phase space more uniformly. It is shown that the modes for this particular behaviour are more representative of the system dynamics than any other set of modes extracted from a non-chaotic response. This is applied to a buckled beam with two permanent magnets and the reduced-order model is validated using both qualitative and quantitative comparisons. [less ▲]

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See detailOn the Expressiveness of Real and Integer Arithmetic Automata
Boigelot, Bernard ULg; Rassart, Stéphane; Wolper, Pierre ULg

in Lecture Notes in Computer Science (1998), 1443

If read digit by digit, a n-dimensional vector of integers represented in base r can be viewed as a word over the alphabet r to the n. It has been known for some time that, under this encoding, the sets ... [more ▼]

If read digit by digit, a n-dimensional vector of integers represented in base r can be viewed as a word over the alphabet r to the n. It has been known for some time that, under this encoding, the sets of integer vectors recognizable by finite automata are exactly those definable in Presburger arithmetic if independence with respect to the base is required, and those definable in a slight extension of Presburger arithmetic if only a specific base is considered. Using the same encoding idea, but moving to infinite words, finite automata on infinite words can recognize sets of real vectors. This leads to the question of which sets of real vectors are recognizable by finite automata, which is the topic of this paper. We show that the recognizable sets of real vectors are those definable in the theory of reals and integers with addition and order, extended with a special base-dependent predicate that tests the value of a specified digit of a number. Furthermore, in the course of proving that sets of vectors defined in this theory are recognizable by finite automata, we show that linear equations and inequations have surprisingly compact representations by automata, which leads us to believe that automata accepting sets of real vectors can be of more than theoretical interest. [less ▲]

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See detailOn the extensions of Barlow-Proschan importance index and system signature to dependent lifetimes
Marichal, Jean-Luc; Mathonet, Pierre ULg

in Journal of Multivariate Analysis (2013), 115

For a coherent system the Barlow-Proschan importance index, defined when the component lifetimes are independent, measures the probability that the failure of a given component causes the system to fail ... [more ▼]

For a coherent system the Barlow-Proschan importance index, defined when the component lifetimes are independent, measures the probability that the failure of a given component causes the system to fail. Iyer (1992) extended this concept to the more general case when the component lifetimes are jointly absolutely continuous but not necessarily independent. Assuming only that the joint distribution of component lifetimes has no ties, we give an explicit expression for this extended index in terms of the discrete derivatives of the structure function and provide an interpretation of it as a probabilistic value, a concept introduced in game theory. This enables us to interpret Iyer's formula in this more general setting. We also discuss the analogy between this concept and that of system signature and show how it can be used to define a symmetry index for systems. [less ▲]

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See detailOn the fairness of centralised decision-making strategies in multi-area power systems
Phulpin, Yannick; Begovic, Miroslav; Petit, Marc et al

in Proceedings of the 16th Power Systems Computation Conference (PSCC-08) (2008)

In this paper, we consider an interconnected power system, where the different Transmission System Operators (TSOs) have agreed to transferring some of their competences to a Centralised Control Center ... [more ▼]

In this paper, we consider an interconnected power system, where the different Transmission System Operators (TSOs) have agreed to transferring some of their competences to a Centralised Control Center (CCC). In such a context, a recurrent difficulty for the CCC is to define decision-making strategies which are fair enough to every TSO of the interconnected system. We address this multiobjective problem when the objective of every TSO can be represented by a real-valued function. We propose an algorithm to elect the solution that leads to the minimisation of the distance with the utopian minimum after having normalised the different objectives. We analyse the fairness of this solution in the sense of economics. We illustrate the approach with the IEEE 118 bus system partitioned in 3 areas having as local objective the minimisation of active power losses, the maximisation of reactive power reserves, or a combination of both criteria. [less ▲]

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See detailOn the feasibility of an ultrafast purely electronic reorganization in lithium hydride
Remacle, Françoise ULg; Kienberger, R.; Krausz, F. et al

in Chemical Physics (2007), 338

Excitation of a coherent electronic wave packet, a linear combination of several electronic stationary states, is discussed with a computational example, the A and B low lying excited states of LiH. Such ... [more ▼]

Excitation of a coherent electronic wave packet, a linear combination of several electronic stationary states, is discussed with a computational example, the A and B low lying excited states of LiH. Such linear combination results in the electron executing a rotation-like motion in the xz plane with a period of 4 fs. The excitation needs to be shorter than this purely electronic reorganization time and yet the mean energy of the photon should be relatively low so that the A and B states are coherently accessed. These two requirements limit the wave form of the few cycle pump pulse. (c) 2007 Elsevier B.V. All rights reserved. [less ▲]

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See detailOn the feasibility of retrieving 16O 18O 16O ozone from high resolution ground-based FTIR spectra
Arlander, D.W.; Barbe, Alain; Bourgeois, M.T. et al

in Proceedings of Atmospheric Spectroscopy Applications, ASA Reims 1993, September 8-10 (1993)

We present evidence of the 16O 18O 16O ozone isotope in the 5 micron region from FTIR solar occultation spectra obtained from the Jungfraujoch Solar Observatory (47°N, 8°E, 3580 m) in Switzerland at a ... [more ▼]

We present evidence of the 16O 18O 16O ozone isotope in the 5 micron region from FTIR solar occultation spectra obtained from the Jungfraujoch Solar Observatory (47°N, 8°E, 3580 m) in Switzerland at a spectral resolution of 0,0025 cm-1 (res. = 1/2L). These spectra clearly show numerous unblended lines of the 16O 18O 16O ozone isotope. Laboratory spectra in the 5 micron region of 16O 18O 16O have been measured and have yielded line positions of the nu1 + nu3 isotopic bands which can eventually lead to their retrieval from measured ground-based solar occultation spectra. [less ▲]

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See detailOn the feeding ecology of the pied kingfisher, Ceryle rudis at Lake Nokoué, Benin. Is there competition with fishermen ?
Laudelout, Arnaud; Libois, Roland ULg

in Cowx I.G. (Ed.) Interactions between fish and birds: implications for management (2003)

Lake Noukoué in southern Benin, is heavily exploited fishery, but it is also inhabited by numerous piscivorous birds, escpecially kingfishers. This study considers the similarity between the diet of ... [more ▼]

Lake Noukoué in southern Benin, is heavily exploited fishery, but it is also inhabited by numerous piscivorous birds, escpecially kingfishers. This study considers the similarity between the diet of kingfishers and fish available on the local market between mid-February to mi-May 1999, durng a low water level preriod. Excretory pellets were collected on the top of breeding banks and inside brood chambers. The diet was determined by comparing the bones recovered from the pellets with a reference collection. Eighteen prey categories were recognised in the 1099 diagnostic items. Kingfishers preyed mostly on cichlids (Sarotherodon melanotheron Rüppell and Hemichromis fasciatus Peters), clupeids (Ethmalosa fimbria (Bowdich)), eleotrids (Kribia sp.) and Hyporhamphus picarti (Val.). Prey size of H. fasciatus ranged from 22 to 73 mm (46.4 +/- 11.6 mm) and S. melanotheron from 24 to 65 mm (44 +/- 9.2 mm). The compositionof the diet varied depending on time and location. Overlap with marketed fish is limitid to S. melanotheron. [less ▲]

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See detailOn the finiteness and uniqueness of the weighted likelihood estimator of ability in polytomous IRT models
Magis, David ULg; Verhelst, Norman

Conference (2014, November 21)

In item response theory (IRT), the weighted likelihood (WL) estimator has become a central method to estimate ability levels of respondents. Primarily introduced with dichotomous IRT models (Warm, 1989 ... [more ▼]

In item response theory (IRT), the weighted likelihood (WL) estimator has become a central method to estimate ability levels of respondents. Primarily introduced with dichotomous IRT models (Warm, 1989), it was later extended to polytomous IRT models (Samejima, 1998). However, very few information is available about the behavior of the WL estimator, and especially about the uniqueness of the ability estimates as well as their finiteness. The purpose of this talk is to establish that with polytomous item response models, the WL estimator of ability always returns finite values. This result is valid for the class of difference models and divide-by-total models, independently of the number of items and the response patterns. However, such estimates may not necessarily be unique, as the WL solving equation may provide several optimal values. Some examples are considered to illustrate both findings. [less ▲]

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See detailOn the forbidden red lines of oxygen in comets
Arpigny, Claude ULg; Manfroid, Jean ULg; Magain, Pierre ULg et al

in Diversity and Similarity of Comets (1987, September 01)

Eighteen spectra of 8 different comets observed at high and medium resolution were analyzed in the 627 to 637 nm region to determine the contributions of the (OI) red doublet and of the various NH2 lines ... [more ▼]

Eighteen spectra of 8 different comets observed at high and medium resolution were analyzed in the 627 to 637 nm region to determine the contributions of the (OI) red doublet and of the various NH2 lines present in this wavelength interval. Results confirm that there exist appreciable variations not only in the (OI)/NH2 ratio, but also in the relative intensities of the NH2 features among themselves, therefore, it is not justified to derive the (OI) line flux from the 630.0 blend, as was done in previous low-resolution work, by assuming a fixed relative strength of the NH2 emission contained in this blend. Mapping of these emissions over the coma is recommended. [less ▲]

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See detailON THE FORMATION OF PHOTOSYSTEM-II CHLOROPHYLL PROTEINS AFTER A SHORT LIGHT FLASH IN ETIOLATED BARLEY LEAVES, AS MONITORED BY INVIVO FLUORESCENCE SPECTROSCOPY
Franck, Fabrice ULg

in Journal of Photochemistry and Photobiology B : Biology (1993), 18(1), 35-40

The biogenesis of photosystem II (PSII) was investigated using 77 K fluorescence spectroscopy in etiolated barley leaves subjected to a millisecond flash which reduced all protochlorophyllide (Pchlide ... [more ▼]

The biogenesis of photosystem II (PSII) was investigated using 77 K fluorescence spectroscopy in etiolated barley leaves subjected to a millisecond flash which reduced all protochlorophyllide (Pchlide) into chlorophyllide (Chlide). In darkness after the flash, a slow chlorophyll (Chl) band shift from 682 to 684 nm was associated with the development of PSII variable fluorescence. Two Chl fluorescence bands at 678 and 687 nm were formed during the shift, the 687 nm band corresponding to the spectrum of the PSII variable fluorescence. The development of PSII fluorescence was inhibited by chloramphenicol and enhanced by cyclobeximide, suggesting a competition between plastid- and nucleus-encoded proteins for Chl binding. [less ▲]

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See detailOn the Formation of Thritionat
Spring, Walthère ULg

in The Chemical News (1892), 65

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See detailOn the formulae of reduction to apparent places of close Polar stars
Folie, François ULg

in Monthly Notices of the Royal Astronomical Society (1892), 52

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See detailOn the frequency of occurrence of a peculiar polyester fibre type found in blue denim textiles
De Wael, Kris; Baes, Christiaan; Lepot, Laurent ULg et al

in Science & Justice (2011), 51(4), 154-162

In a double murder investigation, the victims were found after a prolonged stay in a drainage canal. In spite of the expectations, fibre examination established a multitude of primary and secondary ... [more ▼]

In a double murder investigation, the victims were found after a prolonged stay in a drainage canal. In spite of the expectations, fibre examination established a multitude of primary and secondary transferred fibres. One of these fibre types was a colourless polyester fibre possessing a blue coloured molten fibre end. These matched one of the types present in the suspect's blue denim trousers. The aim of this study was to verify the rarity of this peculiar fibre type and more precisely its presence in blue denim textiles. Over five hundred different blue jeans textiles were examined and only one of these presented exactly the same type. The comparison involved microscopy, microspectrophotometry in the visible range and Raman spectroscopy. The results indicate this fibre type is extremely rare in a blue jeans fabrics and that "standard" blue denim should not be disregarded in case work. [less ▲]

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See detailOn the functional form of a nonlinear vibration absorber
Viguié, V; Kerschen, Gaëtan ULg

in Journal of Sound & Vibration (2010), 329

Due to the frequency–energy dependence of nonlinear oscillations, nonlinear dynamical absorbers present interesting properties for mitigating unwanted vibrations in mechanical systems. Unlike the tuned ... [more ▼]

Due to the frequency–energy dependence of nonlinear oscillations, nonlinear dynamical absorbers present interesting properties for mitigating unwanted vibrations in mechanical systems. Unlike the tuned mass damper, the functional form of a nonlinear absorber is not known a priori and must be determined. This short note addresses this issue when a light-weight nonlinear absorber is attached to a nonlinear primary structure. Numerical simulations demonstrate that the determination of an adequate functional form may be directly linked to the frequency–energy dependence of the primary structure. [less ▲]

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See detailON THE FUNCTIONAL-CHARACTERIZATION OF THE ANALYTIC WAVE-FRONT SET OF AN HYPERFUNCTION
Bastin, Françoise ULg; LAUBIN, P.

in Mathematische Nachrichten (1994), 166

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See detailOn the genetic structure of the Iberian wood mouse (Apodemus sylvaticus) populations. An analyse of mtDNA restriction patterns
Michaux, J; Libois, Roland ULg; Ramalhinho, Maria da Graça et al

in Reig, S. (Ed.) Abstracts of the Euro American mammal congress (1998, July)

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See detailOn the glassy sea: An astronomer's journey -- Tom Gehrels
Manfroid, Jean ULg

in Ciel et Terre (1990), 106

Not Available

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See detailOn the He Weak Variable HD 28843
Manfroid, Jean ULg; Mathys, G.; Cousins, A. W. J.

in Information Bulletin on Variable Stars (1984), 2625

Not Available

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