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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 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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See detailOn simplified handling of state events in time-domain simulation
Fabozzi, Davide ULg; Chieh, Angela S.; Panciatici, Patrick et al

in Proceedings of the 17th PSCC (2011, August)

The power system models typically used in dynamic simulations involve discrete events in addition to the standard differential-algebraic equations. Those events cause the system to jump from one ... [more ▼]

The power system models typically used in dynamic simulations involve discrete events in addition to the standard differential-algebraic equations. Those events cause the system to jump from one continuous behavior to another. Solvers have to handle those jumps. This paper focuses on simplified time simulation where large steps are used in conjunction with stiff-decay integration methods to obtain approximate solutions in short computing times. In the proposed simulation scheme, the simulation time steps are not synchronized with the system jumps, which are treated a posteriori in a corrective step. In this context, the paper analyzes several simple nonlinear models involving limiters, switches, minimum gates, etc. from which some precautions to be taken at the modelling and solving stages are stressed. The paper also reports on results obtained with a representative power system model. [less ▲]

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See detailOn Skinner's disenchantment
Richelle, Marc ULg

in Counselling Psychology Quarterly (1988), 1(2-3), 317-320

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See detailOn some drawbacks and possible improvements of a lagrangian finite element approach for simulating incompressible flows
Cerquaglia, Marco Lucio ULg; Deliège, Geoffrey ULg; Boman, Romain ULg et al

Conference (2015)

In this paper a Lagrangian finite element approach for the simulation of incompressible flows is presented, based on the so-called Particle Finite Element Method (PFEM). The spatial discretization and the ... [more ▼]

In this paper a Lagrangian finite element approach for the simulation of incompressible flows is presented, based on the so-called Particle Finite Element Method (PFEM). The spatial discretization and the definition of the boundary terms are discussed in detail with a specific focus on free-surface flows. Additionally, some problems that can arise from the use of such a method are pointed out. Some numerical examples are given and discussed in the last section of the paper. [less ▲]

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See detailOn some stability properties of the discretization of damped propagation of shallow-water inertia–gravity waves on the Arakawa B-grid
Beckers, Jean-Marie ULg

in Ocean Modelling (1999), 1(2-4), 53-69

We investigate a problem mentioned by Deleersnijder and Campin (Deleersnijder, E., & Campin, J. -M. (1993). Ocean Modelling 97, 2), who looked at the problem of the discretization of inertia–gravity waves ... [more ▼]

We investigate a problem mentioned by Deleersnijder and Campin (Deleersnijder, E., & Campin, J. -M. (1993). Ocean Modelling 97, 2), who looked at the problem of the discretization of inertia–gravity waves in the staggered B-grid. We generalize this study by adding diffusion. General stability conditions are found with the help of Miller's theorem, and the paradox found in Deleersnijder and Campin (Deleersnijder, E., & Campin, J. -M. (1993). Ocean Modelling 97, 2) is discussed. It is argued that it stems from inappropriate application of boundary conditions in conjunction with a Coriolis force treatment which could produce mechanical work. [less ▲]

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See detailOn standardness and I-cosiness
Laurent, Stéphane ULg

in Séminaire de Probabilités (2010), XLIII

The object of study of this work is the invariant characteristics of filtrations in discrete, negative time, pioneered by Vershik. We prove the equivalence between I-cosiness and standardness without ... [more ▼]

The object of study of this work is the invariant characteristics of filtrations in discrete, negative time, pioneered by Vershik. We prove the equivalence between I-cosiness and standardness without using Vershik’s standardness criterion. The equivalence between I-cosiness and productness for homogeneous filtrations is further investigated by showing that the I-cosiness criterion is equivalent to Vershik’s first level criterion separately for each random variable. We also aim to derive the elementary properties of both these criteria, and to give a survey and some complements on the published and unpublished literature. [less ▲]

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See detailOn the (13) CN/(12) CN Isotopic Ratio in Comet Hale-Bopp
Schulz, R.; Arpigny, Claude ULg; Manfroid, Jean ULg et al

in Bulletin of the American Astronomical Society (1997, July 01)

The carbon isotope abundance ratio, (12) C/(13) C, in comets is a key number to their origin. Its accurate determination from ground-based spectroscopy is, however, a difficult task since the observable ... [more ▼]

The carbon isotope abundance ratio, (12) C/(13) C, in comets is a key number to their origin. Its accurate determination from ground-based spectroscopy is, however, a difficult task since the observable emissions of (13) C-containing molecules are very weak. Due to its exceptional brightness, comet Hale-Bopp provided a unique opportunity to look for (13) C and derive the (12) C/(13) C isotopic ratio. We observed the comet with the high-resolution spectrograph SOFIN mounted on the 2.56m Nordic Optical Telescope on La Palma, Canary Islands. High-resolution spectra of the R-branch of the CN (0-0) band were obtained between Apr. 7 and 13, 1997, when the comet was at r = 0.9 AU and Delta = 1.4 AU. Owing to the heliocentric velocity effect on the fluorescence excitation rates, this period was particularly favourable to search for the R(8) and R(7) emission lines of the (13) CN isotope. Because of the strong continuum in the coma of Hale-Bopp we took our measurements at a certain location in the coma away from the nucleus and from any dust jets. Our first preliminary reduction and analysis show, after careful continuum subtraction, a clear detection of a line at the position predicted for R(8) and and an indication of a line at the predicted position of R(7). The R(8) line can be used to determine the (12) C/(13) C isotopic ratio and the first preliminary values will be given. [less ▲]

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See detailOn the accuracy of adults’ auditory perception of normophonic and dysphonic children’s personality.
Verduyckt, Ingrid; Remacle, Marc; Morsomme, Dominique ULg

in Logopedics, Phoniatrics, Vocology (in press)

We investigated the accuracy of auditory inferences of personality of Belgian children with vocal fold nodules (VFN). External judges (N=57) were asked to infer the personality of normophonic (NP ... [more ▼]

We investigated the accuracy of auditory inferences of personality of Belgian children with vocal fold nodules (VFN). External judges (N=57) were asked to infer the personality of normophonic (NP) children and children with VFN (N=10) on the basis of vowels and sentences. The auditory inferred profiles were compared to the actual personality of NP and VFN children. Positive and partly accurate inferences of VFN children’s personality were made on the basis of connected speech, while sustained vowels yielded negative and inaccurate inferences of personality traits of children with VFN. Dysphonic voice quality, as defined by the overall severity of vocal abnormality, conveyed inaccurate and low degrees of Extraversion. This effect was counterbalanced in connected speech by faster speaking rate that accurately conveyed higher degrees of Extraversion, a characteristic trait of VFN children’s actual personality. [less ▲]

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See detailOn the accuracy of analytical models of TCP throughput
El Khayat, Ibtissam; Geurts, Pierre ULg; Leduc, Guy ULg

in Lecture Notes in Computer Science (2006, May), 3976

Based on a large set of TCP sessions we first study the accuracy of two well-known analytical models (SQRT and PFTK) of the TCP average rate. This study shows that these models are far from being accurate ... [more ▼]

Based on a large set of TCP sessions we first study the accuracy of two well-known analytical models (SQRT and PFTK) of the TCP average rate. This study shows that these models are far from being accurate on average. Actually, our simulations show that 70% of their predictions exceed the boundaries of TCP-Friendliness, thus questioning their use in the design of new TCP-Friendly transport protocols. Our study also shows that the inaccuracy of the PFTK model is largely due to its inability to make the distinction between the two packet loss detection methods used by TCP: triple duplicate acknowledgments or timeout expirations. We then use supervised learning techniques to infer models of the TCP rate. These models show important accuracy improvements when they take into account the two types of losses. This suggests that analytical model of TCP throughput should certainly benefit from the incorporation of the timeout loss rate. [less ▲]

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See detailOn the accuracy of the reduction of UVBY photometry
Manfroid, Jean ULg; Heck, A.

in Astronomy and Astrophysics (1984), 132

By simulating uvby observations under various conditions, an analysis has been made of the precision reachable by a photometric reduction algorithm proposed in an earlier paper (Manfroid and Heck, 1983 ... [more ▼]

By simulating uvby observations under various conditions, an analysis has been made of the precision reachable by a photometric reduction algorithm proposed in an earlier paper (Manfroid and Heck, 1983). The influence of variations in parameters, such as the number of nights or the number of standard stars, is discussed. It is shown how the grouping of nights in the reduction procedure allows the observer to spend less time on standard stars measurements, while improving the accuracy of the results. The difficulty of giving a realistic value for the precision of the reductions in actual conditions is stressed. The inclusion of secondary standards is also recommended. [less ▲]

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See detailOn the accurate selection of asymptotic detection thresholds for Infit and Outfit indexes of person fit
Magis, David ULg; Raîche, Gilles; Béland, Sébastien

Conference (2012, April 11)

It exists a bunch of person fit indexes but Lz (Drasgow, Levine, & Williams, 1985), Infit mean square W (Wright & Masters, 1982) and Outfit mean square U (Wright & Stone, 1979) are certainly the most ... [more ▼]

It exists a bunch of person fit indexes but Lz (Drasgow, Levine, & Williams, 1985), Infit mean square W (Wright & Masters, 1982) and Outfit mean square U (Wright & Stone, 1979) are certainly the most popular. However, they have the undesirable property that their limiting distribution depends on the true ability level, which is generally unknown. In addition, the asymptotic distribution of U and W indexes was not clearly stated. Snijders (2001) proposed a generalization of the index Lz to incorporate estimated ability levels in its computation, and derived subsequent asymptotic normality of this modified Lz* index. The purpose of this talk is threefold. First, the generalization of Lz to Lz* is briefly sketched. Second, it is shown how this generalization can be successfully applied to both U and W indexes, yielding generalized U* and W* indexes respectively. Third, the accuracy of generalized indexes in detecting person (mis)fit is assessed through a simulation study. Three situations were investigated: (a) absence of misfit; (b) presence of cheating (yielding spuriously high scores); (c) presence of inattention (yielding spuriously low scores). Several conditions were varied, such as test length and aberrance rates when misfit was introduced. Response patterns were generated under the Rasch model and maximum likelihood estimation was performed to obtain the ability estimates. Several significance levels were selected. It is observed, that the generalized indexes Lz*, U* and W* better recover the significance level than their standard alternatives Lz, U and W respectively, while they are more powerful in identifying the two types of person misfit. In particular, the modified index W* has the best improvement in performance with respect to its original version W. It is concluded that Snijders' generalization of Lz index to Lz* is also accurate for U and W indexes under Rasch modelling. Possible extensions to other person fit indexes, such as ECI indexes (Tatsuoka, 1984), other ability estimators, and other IRT models are eventually briefly discussed. [less ▲]

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