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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 ▲]

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See detailNote on the measurement of the thermal conductivity and the double peak structure in high-Tc superconductors
Bougrine, Hassan ULg; Pekala, M.

in Superconductor Science & Technology (1997), 10(8), 621-623

We show that low-temperature measurements of the thermal conductivity of high-T-c superconductors can sometimes reveal a double peak structure depending on the experimental set-up used.

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See detailA Note On The Rate Of Passage Of Digesta In Pigs Ileo-Rectostomized Or Fitted With An Ileal T-Cannula
Leterme, Pascal; Pirard, L.; Thewis, André ULg et al

in Animal Production (1991), 53(2), 253-256

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See detailA note on the response to simple shear of elasto-plastic materials with isotropic hardening
Cescotto, Serge ULg; Habraken, Anne ULg

in European Journal of Mechanics A : Solids (1991), 10(1), 1-13

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See detailA note on the resting behaviour of cows before and after calving in two different housing systems
Dechamps, P.; Nicks, Baudouin ULg; Canart, Bernard et al

in Applied Animal Behaviour Science (1989), 23(1-2), 99-105

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See detailA note on the size-fractionated pigments of the phytoplankton of the Strait of Magellan (February-March 1991)
Saggiomo, Vincenzo; Mangoni, Olga; Borriello, C. et al

in Oebalia : International Journal of Marine Biology and Oceanography (1994), XX

During an oceanographic cruise, carried out at the end of the austral summer (February-March 1991) in the Strait of Magellan, spatial patterns of size-fractionated chlorophyll and primary production were ... [more ▼]

During an oceanographic cruise, carried out at the end of the austral summer (February-March 1991) in the Strait of Magellan, spatial patterns of size-fractionated chlorophyll and primary production were studied in relation to hydrographic patterns. Phytoplankton biomass, in terms of active Chl a, ranged between 10 and 51 mg m-2 and primary production between 275 and 1 170 mg C m-2 d-1. The most important features concern the confinement of the microphytoplanktonic fraction to the Pacific opening and to the embayements between the two Narrows. In the internal part of the Strait, an uniform dimensional structure (< 5 um) of phytoplankton communities was observed, with the picophytoplanktonic fraction always dominant. [less ▲]

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See detailA note on the use of fluorescently labelled algae for the determination of gut passage time in Bosmina and Daphnia
Cauchie, Henry-Michel ULg; Deguée, N.; Joaquim-Justo, Célia ULg et al

in Verhandlungen der Internationalen Vereinigung für Theoretische und Angewandte Limnologie = Proceedings of the International Association of Theoretical and Applied Limnology (2001), 27

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See detailA Note on the Use of the Modified Value-at-Risk
Cavenaile, Laurent ULg; Lejeune, Thomas ULg

in Journal of Alternative Investments (2012), 14(4), 79-83

While the Modified Value-at-Risk (or Cornish Fisher Value-at-Risk) has been quite extensively used by practitioners and academics since its introduction, we show that it can be consistently used only over ... [more ▼]

While the Modified Value-at-Risk (or Cornish Fisher Value-at-Risk) has been quite extensively used by practitioners and academics since its introduction, we show that it can be consistently used only over a limited interval of confidence level. Confidence level below 95.84% should never be used for the Modified Value-at-Risk to be consistent with investors' preferences for kurtosis. In addition, the use of higher confidence level is restricted by the value of the skewness. Failure to respect these restrictions on confidence levels results in mistakenly assessing assets' risk and potentially in overweighting assets which exhibit undesirable properties in terms of higher moments. [less ▲]

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