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See detailOn period determination methods
Heck, A.; Manfroid, Jean ULg; Mersch, G.

in Astronomy and Astrophysics. Supplement Series (1985), 59

It is noted that the two large families of period determination techniques based on the Fourier transform and on the nonparametric algorithms derived from the theta-criterion by Lafler and Kinman (1965 ... [more ▼]

It is noted that the two large families of period determination techniques based on the Fourier transform and on the nonparametric algorithms derived from the theta-criterion by Lafler and Kinman (1965) are not equivalent to each other under general conditions. Instead, at best, all criteria may be expressed as the ratio of two quadratic forms. Numerical simulations have been conducted in order to compare the performance of Deeming's (1975) Fourier method, Burki et al.'s (1978) autocorrelation method, Lafler and Kinman's (1965) method, and the Renson (1978) and Stellingwerf (1978) methods. When applied to single-periodic phenomena, the tests indicate that none of the methods is clearly superior. [less ▲]

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See detailOn periodic reference tracking using batch-mode reinforcement learning with application to gene regulatory network control
Sootla, Aivar; Strelkowa, Natajala; Ernst, Damien ULg et al

in Proceedings of the 52nd Annual Conference on Decision and Control (CDC 2013) (2013, December)

In this paper, we consider the periodic reference tracking problem in the framework of batch-mode reinforcement learning, which studies methods for solving optimal control problems from the sole knowledge ... [more ▼]

In this paper, we consider the periodic reference tracking problem in the framework of batch-mode reinforcement learning, which studies methods for solving optimal control problems from the sole knowledge of a set of trajectories. In particular, we extend an existing batch-mode reinforcement learning algorithm, known as Fitted Q Iteration, to the periodic reference tracking problem. The presented periodic reference tracking algorithm explicitly exploits a priori knowledge of the future values of the reference trajectory and its periodicity. We discuss the properties of our approach and illustrate it on the problem of reference tracking for a synthetic biology gene regulatory network known as the generalised repressilator. This system can produce decaying but long-lived oscillations, which makes it an interesting application for the tracking problem. [less ▲]

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See detailOn periodical oscillations of Lurie systems with discontinuous nonlinearity
Efimov, Denis ULg

in Proc. 17th IFAC WC, Seoul, Korea (2008)

Sufficient conditions of global attracting limit cycle existence for Lurie system with sign nonlinearity are presented. It is assumed that the linear part of the system is output stabilizable, the ... [more ▼]

Sufficient conditions of global attracting limit cycle existence for Lurie system with sign nonlinearity are presented. It is assumed that the linear part of the system is output stabilizable, the nonlinearity has linear negative term plus positive one proportional to the output sign. Conditions of oscillatority in the sense of Yakubovich for this class of systems are also reestablished. [less ▲]

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See detailOn peut se sentir wallon et belge
Jacquemain, Marc ULg

Article for general public (2008)

L'interview défend l'idée d'une identité wallonne "non nationale" qui se sent donc à l'aise au sein de la Belgique.

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See detailOn photometric standards and color transformation
Manfroid, Jean ULg

in Calibration of Fundamental Stellar Quantities (1985)

The author has carried out a preliminary investigation of a method of observation and reduction which leads to a large improvement in the accuracy of the color transformation of photometric measurements ... [more ▼]

The author has carried out a preliminary investigation of a method of observation and reduction which leads to a large improvement in the accuracy of the color transformation of photometric measurements. This method involves the use of extra filters for some of the observations. It is argued that the better precision obtained is well worth the additional telescope work. [less ▲]

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See detailOn posterior probability and significance level: application to the power spectrum of HD 49 933 observed by CoRoT
Appourchaux, T.; Samadi, R.; Dupret, Marc-Antoine ULg

in Astronomy and Astrophysics (2009), 506

Context: The CoRoT mission provides asteroseismic data of very high quality allowing one to adopt new statistical approaches for mode detection in power spectra, especially with respect to testing the ... [more ▼]

Context: The CoRoT mission provides asteroseismic data of very high quality allowing one to adopt new statistical approaches for mode detection in power spectra, especially with respect to testing the null hypothesis (H{0}, which assumes that what is observed is pure noise). Aims: We emphasize that the significance level when rejecting the null hypothesis can lead to the incorrect conclusion that the H{0} hypothesis is unlikely to occur at that significance level. We demonstrate that the significance level is unrelated to the posterior probability of H{0}, given the observed data set, and that this posterior probability is very much higher than implied by the significance level. Methods: We use Bayes theorem to derive the posterior probability of that H{0} is true assuming an alternative hypothesis H{1} that a mode is present, taking some prior for the mode height, mode amplitude and linewidth. Results: We compute the posterior probability of H{0} for the p modes detected on HD 49 933 by CoRoT. Conclusions: We conclude that the posterior probability of H{0} provide a much more conservative quantification of the mode detection than the significance level. This framework can be applied to any similar stellar power spectra obtained to complete asteroseismology. The CoRoT space mission, launched on 2006 December 27, was developed and is operated by the CNES, with participation of the Science Programs of ESA, ESA's RSSD, Austria, Belgium, Brazil, Germany and Spain. [less ▲]

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See detailOn Projection-Based Model Reduction of Biochemical Networks Part I: The Deterministic Case
Sootla, Aivar ULg; Anderson, James

in Proceedings of the 53rd IEEE Conference on Decision and Control (2014, December)

This paper addresses the problem of model reduction for dynamical system models that describe biochemical reaction networks. Inherent in such models are properties such as stability, positivity and ... [more ▼]

This paper addresses the problem of model reduction for dynamical system models that describe biochemical reaction networks. Inherent in such models are properties such as stability, positivity and network structure. Ideally these properties should be preserved by model reduction procedures, although traditional projection based approaches struggle to do this. We propose a projection based model reduction algorithm which uses generalised block diagonal Gramians to preserve structure and positivity. Two algorithms are presented, one provides more accurate reduced order models, the second provides easier to simulate reduced order models. [less ▲]

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See detailOn Projection-Based Model Reduction of Biochemical Networks Part II: The Stochastic Case
Sootla, Aivar ULg; Anderson, James

in Proceedings of the 53rd IEEE Conference on Decision and Control (2014, December)

In this paper, we consider the problem of model order reduction of stochastic biochemical networks. In particular, we reduce the order of (the number of equations in) the Linear Noise Approximation of the ... [more ▼]

In this paper, we consider the problem of model order reduction of stochastic biochemical networks. In particular, we reduce the order of (the number of equations in) the Linear Noise Approximation of the Chemical Master Equation, which is often used to describe biochemical networks. In contrast to other biochemical network reduction methods, the presented one is projection-based. Projection-based methods are powerful tools, but the cost of their use is the loss of physical interpretation of the nodes in the network. In order alleviate this drawback, we employ structured projectors, which means that some nodes in the network will keep their physical interpretation. For many models in engineering, finding structured projectors is not always feasible; however, in the context of biochemical networks it is much more likely as the networks are often (almost) monotonic. To summarise, the method can serve as a trade-off between approximation quality and physical interpretation, which is illustrated on numerical examples. [less ▲]

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See detailOn protocols and measures for the validation of supervised methods for the inference of biological networks
Schrynemackers, Marie ULg; Kuffner, Robert; Geurts, Pierre ULg

in Frontiers in genetics (2013), 4(262),

Networks provide a natural representation of molecular biology knowledge, in particular to model relationships between biological entities such as genes, proteins, drugs, or diseases. Because of the ... [more ▼]

Networks provide a natural representation of molecular biology knowledge, in particular to model relationships between biological entities such as genes, proteins, drugs, or diseases. Because of the effort, the cost, or the lack of the experiments necessary for the elucidation of these networks, computational approaches for network inference have been frequently investigated in the literature. In this paper, we examine the assessment of supervised network inference. Supervised inference is based on machine learning techniques that infer the network from a training sample of known interacting and possibly non-interacting entities and additional measurement data. While these methods are very effective, their reliable validation in silico poses a challenge, since both prediction and validation need to be performed on the basis of the same partially known network. Cross-validation techniques need to be specifically adapted to classification problems on pairs of objects. We perform a critical review and assessment of protocols and measures proposed in the literature and derive specific guidelines how to best exploit and evaluate machine learning techniques for network inference. Through theoretical considerations and in silico experiments, we analyze in depth how important factors influence the outcome of performance estimation. These factors include the amount of information available for the interacting entities, the sparsity and topology of biological networks, and the lack of experimentally verified non-interacting pairs. [less ▲]

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See detailOn Psychologizing School
Notturni, Loris ULg

in Petrov, Vesselin (Ed.) Applied and Experimental Philosophy in the Knowledge Based Society East and West. Proceedings of XXVI Varna International Philosophical School (2012)

What is school ? Though this question is philosophical – if we keep in mind the historical tight bind between philosophy and teaching – it is nowadays considered exclusively as psycho-sociological matter ... [more ▼]

What is school ? Though this question is philosophical – if we keep in mind the historical tight bind between philosophy and teaching – it is nowadays considered exclusively as psycho-sociological matter. In educational relations (e.g. between children and their teacher), psychology is the vantage point : then pedagogy is above all psycho-pedagogy. At the same time we cannot today in Belgium deny a heavy, deep crisis in fundamental education any more. This situation may sanction pessimistic behaviors which often lead to inactivity and passivity. For my part, I would say this crisis is characterized by a current psychological aporia. So I must ask a new question : What should school be ? From the Kantian interrogation about the requirements of education – which is an art, not a science - I will draw some philosophical and pragmatic ways to overcome this psychological puzzle. [less ▲]

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See detailOn Reflections and Reflexiveness: Positioning the Self, Enframing the Other?
Thoreau, François ULg

Conference (2010, October 01)

STS scholars are increasingly engaged with science and technology practitioners, scientists, engineers and the like. The actual dynamics of these engagements differ from one project, framework or school ... [more ▼]

STS scholars are increasingly engaged with science and technology practitioners, scientists, engineers and the like. The actual dynamics of these engagements differ from one project, framework or school to the next. However, to be reflexive, such engagements exercises need to deal at some point with the ambiguous ethical relationships between engager and engaged. In an attempt to disambiguate some of these interactive ties, we begin by considering the respective agendas of involved participants. To do so, we draw upon Despret’s perspectives about experiments on animals and the paradoxical relationships they give rise to. We identify the implied injunctions among STS scholars not only to "be reflexive" but also to reflect back onto practitioners their own worldviews. We then consider some of the ethical tensions, ambiguities and paradoxes between and emerging out of reflexive engagements of the self and of the other. Particularly, we explore to what extent reflexive engagements constitute ends in themselves or means to other ends. We ground this analysis in empirical evidence from an engagement study conducted in a large-scale R&D center in Flanders, Belgium. [less ▲]

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See detailOn Reflections and Reflexivity: Unpacking Research Dispositifs
Thoreau, François ULg

in Zülsdorf, Torben; Coenen, Christopher; Ferrari, Arianna (Eds.) et al Quantum Engagements: Social Reflections of Nanoscience and Emerging Technologies (2011)

Abstract. Science and Technology Studies (STS) scholars increasingly engage with science and technology (S&T) practitioners, scientists, engineers, and the like. The actual dynamics of these engagements ... [more ▼]

Abstract. Science and Technology Studies (STS) scholars increasingly engage with science and technology (S&T) practitioners, scientists, engineers, and the like. The actual dynamics of these engagements differ from one project, framework or school to the next. However, to be reflexive, such engagements need at some point to deal with the ambiguous relationship between ‘engager’ and ‘engaged’. In an attempt to disambiguate these interactive ties, this chapter takes inspiration from Vinciane Despret, a philosopher of science who has provided ethnographic studies of ethologists. It specifically draws on two of Despret’s arguments about experiments on animals, more precisely rats, and the paradoxical relationships to which they give rise. By means of analogy, it then illustrates the similar ways in which we, as STS scholars, might happen to frame our interactions with S&T practitioners. It argues that any experimental research dispositif necessarily implies a specific relationship dynamic with whoever is engaged. This should not be considered as an obstacle, but instead an opportunity for learning—yet only if the dispositif is open to protest. The analysis here took shape during an engagement study conducted at a large-scale R&D center in Flanders, Belgium. It is informed by ongoing involvement in a broader research project (STIR) that aims at fostering reflexivity among S&T practitioners. [less ▲]

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See detailOn relative merits of Implicit/Explicit Algorithms for Transient Problems in Metal Forming Simulation
Ponthot, Jean-Philippe ULg; Hogge, Michel ULg

in Proc. of the Int. Conf. on Numerical Methods for Metal Forming in Industry (1994)

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See detailOn Relativistic Scalar and Vector-Mesons with Harmonic Oscillator-Like Interactions
Debergh, N.; Ndimubandi, J.; Strivay, David ULg

in Zeitschrift Fur Physik C-Particles and Fields (1992), 56(3), 421-425

Relativistic descriptions for spin 0 and 1 particles of nonzero restmasses are known for a long time as the so-called Kemmer or Sakata-Taketani formulations. Through harmonic oscillatorlike interactions ... [more ▼]

Relativistic descriptions for spin 0 and 1 particles of nonzero restmasses are known for a long time as the so-called Kemmer or Sakata-Taketani formulations. Through harmonic oscillatorlike interactions, we study the nonrelativistic limit of the corresponding wave equations in connection with expected spin-orbit terms. Typical Foldy-Wouthuysen developments are included in these approaches with exact results up to required orders for interacting vector mesons only. [less ▲]

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See detailOn Sally Ledger and Roger Luckhurst’s The Fin de Siècle: A Reader in Cultural History c.1880-1900
Steyaert, Kris ULg

in Journal of Gender Studies (2002), 11(2), 192-193

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See detail"On se débrouille", or how to be a good judge when the state lets you down?
Andreetta, Sophie ULg; Kolloch, Annalena

Conference (2015, July)

Over the last couple of years, Beninese magistrates have been on strike for months in a row. In 2012, it was about the Ministry of justice implying corruption issues. In 2013, it was about independence ... [more ▼]

Over the last couple of years, Beninese magistrates have been on strike for months in a row. In 2012, it was about the Ministry of justice implying corruption issues. In 2013, it was about independence and fear of political infringement. In 2014, it was about the most recent appointments. When it comes to judges from the bench, most of them complain about their substantial workload, low pay and poor working conditions. They also highlight the discrepancies between the magistrate’s social status and what their families expect from them, the standards of living that people assume that they have. In short, there seems to be a professional malaise within the Beninese bench, who feel like the state is letting them down, yet judges also insist on the importance of their work, and of doing it right. This is why, for the purpose of this paper, we will be looking at the discourses and representations of Beninese judges on their own social and professional status. What does it mean to be a judge in Benin today? Why do young lawyers choose that professional path over other legal careers? How do they ‘do their job right’ and what are the obstacles to it? Considering both age and gender, we are also trying to look at what it means to be a civil servant today, when the state is no longer the only – or the most promising – employer for legal practitioners. [less ▲]

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See detailOn signature-based expressions of system reliability
Marichal, Jean-Luc; Mathonet, Pierre ULg; Waldhauser, Tamás

in Journal of Multivariate Analysis (2011), 102(10), 1410-1416

The concept of signature was introduced by Samaniego for systems whose components have i.i.d. lifetimes. This concept proved to be useful in the analysis of theoretical behaviors of systems. In particular ... [more ▼]

The concept of signature was introduced by Samaniego for systems whose components have i.i.d. lifetimes. This concept proved to be useful in the analysis of theoretical behaviors of systems. In particular, it provides an interesting signature-based representation of the system reliability in terms of reliabilities of k-out-of-n systems. In the non-i.i.d. case, we show that, at any time, this representation still holds true for every coherent system if and only if the component states are exchangeable. We also discuss conditions for obtaining an alternative representation of the system reliability in which the signature is replaced by its non-i.i.d. extension. Finally, we discuss conditions for the system reliability to have both representations. [less ▲]

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