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See detailA note on behavioral tolerance to meprobamate
Richelle, Marc ULg

in Journal of the Experimental Analysis of Behavior (1965), 8(1), 45-46

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See detailA note on finite-sample efficiencies of estimators for the minimum volume ellipsoid
Croux, C.; Haesbroeck, Gentiane ULg

in Journal of Statistical Computation & Simulation (2002), 72(7), 585-596

Among the most well known estimators of multivariate location and scatter is the Minimum Volume Ellipsoid (MVE). Many algorithms have been proposed to compute it. Most of these attempt merely to ... [more ▼]

Among the most well known estimators of multivariate location and scatter is the Minimum Volume Ellipsoid (MVE). Many algorithms have been proposed to compute it. Most of these attempt merely to approximate as close as possible the exact MVE, but some of them led to the definition of new estimators which maintain the properties of robustness and affine equivariance that make the MVE so attractive. Rousseeuw and van Zomeren (1990) used the (p+1)- subset estimator which was modified by Croux and Haesbroeck (1997) to give rise to the averaged (p+1)- subset estimator . This note shows by means of simulations that the averaged (p+1)-subset estimator outperforms the exact estimator as far as finite-sample efficiency is concerned. We also present a new robust estimator for the MVE, closely related to the averaged (p+1)-subset estimator, but yielding a natural ranking of the data. [less ▲]

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See detailNote on formation of stellar absorption lines
Swings, Polydore ULg; Struve, Otto

in Publications of the American Astronomical Society (1936), 8

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See detailA note on longevity enhancing investment
Eeckhoudt, Louis; Pestieau, Pierre ULg

in Economics Letters (2008)

We argue that risk averse individuals prefer to increase their longevity in the direction of rectangularization of the survival curve instead of an upward shift of that curve. Risk aversion is measured by ... [more ▼]

We argue that risk averse individuals prefer to increase their longevity in the direction of rectangularization of the survival curve instead of an upward shift of that curve. Risk aversion is measured by the concept of fear of ruin. [less ▲]

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See detailA note on molecular absorption in interstellar space
Swings, Polydore ULg

in Monthly Notices of the Royal Astronomical Society (1937), 97(3), 212-215

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See detailA note on moments of scaling functions
Bastin, Françoise ULg; Nicolay, Samuel ULg

in Rocky Mountain Journal of Mathematics (2004), 34(4, Winter), 1197-1206

In this note we give a proof of a reproducing formula for polynomials using natural decay hypothesis. This leads to a new exact formula for computation of moments of even order.

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See detailNote on singular optima in laminate design problems
Bruyneel, Michael; Duysinx, Pierre ULg

in Structural and Multidisciplinary Optimization (2006), 31(2), 156-159

This paper studies the design of laminates subject to restrictions on the ply strength. The minimum weight design is considered. It is shown that this formulation includes singular optima, which are ... [more ▼]

This paper studies the design of laminates subject to restrictions on the ply strength. The minimum weight design is considered. It is shown that this formulation includes singular optima, which are similar to the ones observed in topology optimization including local stress constraints. In laminate design, these singular optima are linked to the removal of 'zero thickness' plies from the stacking sequence. It is shown how the fiber orientation variables can circumvent the singularity by relaxing the strength constraints related to such vanishing plies. This demonstrates the key role of fiber orientations in the optimization of laminates and the need for their efficient treatment as design variables. [less ▲]

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See detailA note on stability, robustness and performance of output feedback nonlinear model predictive control
Imsland, Lars; Findeisen, Rolf; Bullinger, Eric ULg et al

in Journal of Process Control (2003), 13(7), 633-644

In recent years. nonlinear model predictive control (NMPC) schemes have been derived that guarantee stability of the closed loop under the assumption of full state information. However, only limited ... [more ▼]

In recent years. nonlinear model predictive control (NMPC) schemes have been derived that guarantee stability of the closed loop under the assumption of full state information. However, only limited advances have been made with respect to output feedback in the framework of nonlinear predictive control. This paper combines stabilizing instantaneous state feedback NMPC schemes with high-gain observers to achieve output feedback stabilization. For a uniformly observable MIMO system class it is shown that the resulting closed loop is asymptotically stable. Furthermore, the output feedback NMPC scheme recovers the performance of the state feedback in the sense that the region of attraction and the trajectories of the state feedback scheme can be recovered to any degree of accuracy for large enough observer gains, thus leading to semi-regional results. Additionally, it is shown that the output feedback controller is robust with respect to static sector bounded nonlinear input uncertainties. (C) 2003 Elsevier Ltd. All rights reserved. [less ▲]

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See detailA note on stars with nebulous absorption lines
Swings, Polydore ULg; Struve, Otto

in Publications of the Astronomical Society of the Pacific [=PASP] (1940), 52

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See detailA note on syndeticity, recognizable sets and Cobham's theorem
Rigo, Michel ULg; Waxweiler, Laurent ULg

in Bulletin of the European Association for Theoretical Computer Science (2006), 88

In this note, we give an alternative proof of the following result. Let p,q>=2 be two multiplicatively independent integers. If an infinite set of integers is both p- and q-recognizable, then it is ... [more ▼]

In this note, we give an alternative proof of the following result. Let p,q>=2 be two multiplicatively independent integers. If an infinite set of integers is both p- and q-recognizable, then it is syndetic. Notice that this result is needed in the classical proof of the celebrated Cobham’s theorem. Therefore the aim of this paper is to complete [13] and [1] to obtain an accessible proof of Cobham’s theorem. [less ▲]

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See detailA note on the age of radioactive tracers
Delhez, Eric ULg; Deleersnijder, Eric; Mouchet, Anne ULg et al

in Journal of Marine Systems (2003), 38(3-4), 277-286

wThe age of a water mass is often estimated experimentally using the radio-age computed from the distribution of a radioactive tracer (radiocarbon, helium-tritium). Deleersnijder et al. [J. Mar. Syst. 28 ... [more ▼]

wThe age of a water mass is often estimated experimentally using the radio-age computed from the distribution of a radioactive tracer (radiocarbon, helium-tritium). Deleersnijder et al. [J. Mar. Syst. 28 (2001) 229.] have shown that the radio-age underestimates the age of the water and is larger than the age of the radioactive tracer used for its evaluation. This result is generalized here to radio-ages computed from the ratio of two radioactive tracers. The differences between the different ages are also studied analytically and numerically as functions of the decay rate of the radioactive tracers. For small decay rates, the difference between the age of the water mass and the radio-age is shown to be proportional to the decay rate. It depends also on the level of mixing in the system; even radioactive tracers with small decay rates can provide poor estimates of the age of the water mass in a strongly diffusive flow. For small half lives, both the radio-age and the age of radioactive tracers decrease as the inverse of the square root of the decay rate. The same analysis applies to some extent to the estimates of the age of a water mass from stable tracers with known time dependent sources (e.g. chloroflurocarbons). (C) 2002 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailA Note On The Comparison Of Methods For Estimating The Ileal Digestibility Of Amino-Acids In Pigs
Leterme, Pascal; Pirard, L.; Thewis, André ULg

in Animal Production (1991), 52(1), 404-406

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See detailA note on the effect of selection on linkage analysis for quantitative traits
Coppieters, Wouter ULg; Mackinnon, M.; Georges, Michel ULg

in Journal of Heredity (1998)

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See detailA note on the equivalence between observed and expected information functions with polytomous IRT models
Magis, David ULg

in Journal of Educational & Behavioral Statistics (2015), 40

The purpose of this note is to study the equivalence of observed and expected (Fisher) information functions with polytomous item response theory (IRT) models. It is established that observed and expected ... [more ▼]

The purpose of this note is to study the equivalence of observed and expected (Fisher) information functions with polytomous item response theory (IRT) models. It is established that observed and expected information functions are equivalent for the class of divide-by-total models (including partial credit, generalized partial credit, rating scale and nominal response models), but not for the class of difference models (including the graded response and modified graded response models). Yet, observed information function remains positive in both classes. Straightforward connections with dichotomous IRT models and further implications are outlined. [less ▲]

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See detailA note on the formation of stellar absorption lines
Swings, Polydore ULg; Struve, Otto

in Astrophysical Journal (1936), 83(3), 238-244

Microphotometer measures of the total absorptions of lines of O II within the wing of Hγ, and of CaH within the wing of HЄ, show departures from the normal absorptions predicted from the multiplet ... [more ▼]

Microphotometer measures of the total absorptions of lines of O II within the wing of Hγ, and of CaH within the wing of HЄ, show departures from the normal absorptions predicted from the multiplet intensities of these lines. The departures increase with the wing absorption, but the effect is more pronounced for O II than for CaH. Eddington's theory of absorption lines leads to a theoretical evaluation of the effect. The remaining discrepancies between this theory and actual observation are unexplained. [less ▲]

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See detailA note on the influence of pairwise misclassification in two-way tables
Magis, David ULg; Gérard, Paul ULg

in Journal of Statistical Computation & Simulation (2006), 76

The influence of subject misclassification on log-linear analysis of two-way contingency tables is investigated. We define pairwise misclassification and focus on both deviance and Pearson statistics as ... [more ▼]

The influence of subject misclassification on log-linear analysis of two-way contingency tables is investigated. We define pairwise misclassification and focus on both deviance and Pearson statistics as goodness-of-fit criteria for testing independence between the variables. Attention is paid to the extremal values of the test statistics that can be reached on the basis of the data set. We derive theoretical properties and use them to detect potentially troubling cells in a simple computing routine. Examples illustrate our purpose. [less ▲]

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See detailA note on the item information function of the four-parameter logistic model
Magis, David ULg

in Applied Psychological Measurement (2013), 37

This paper focuses on four-parameter logistic (4PL) model (Barton & Lord, 1981) as an extension of the usual three-parameter logistic (3PL) model with an upper asymptote possibly different from one. For a ... [more ▼]

This paper focuses on four-parameter logistic (4PL) model (Barton & Lord, 1981) as an extension of the usual three-parameter logistic (3PL) model with an upper asymptote possibly different from one. For a given item with fixed item parameters, Lord (1980) derived the value of the latent ability level that maximizes the item information function under the 3PL model. The purpose of this paper is to extend this result to the 4PL model. A generic and algebraic method is developed for that purpose. The result is practically illustrated by an example and several potential applications of this result are outlined. [less ▲]

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See detailA note on the linearly weighted kappa coefficient for ordinal scales
Vanbelle, Sophie ULg; Albert, Adelin ULg

in statistical methodology (2009), 6

A frequent criticism formulated against the use of weighted kappa coeffcients is that the weights are arbitrarily defined. We show that using linear weights for a K-ordinal scale is equivalent to deriving ... [more ▼]

A frequent criticism formulated against the use of weighted kappa coeffcients is that the weights are arbitrarily defined. We show that using linear weights for a K-ordinal scale is equivalent to deriving a kappa coeffcient from K-1 embedded 2 x 2 tables. [less ▲]

Detailed reference viewed: 81 (13 ULg)