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See detailPIONIER: a visitor instrument for VLTI
Berger, Jean-Philippe; Zins, G.; Lazareff, B. et al

in Danchi, W. C.; Delplancke, F.; Rajagopal, J. K. (Eds.) Optical and Infrared Interferometry II (2010, July)

PIONIER is a 4-telescope visitor instrument for the VLTI, planned to see its first fringes in 2010. It combines four ATs or four UTs using a pairwise ABCD integrated optics combiner that can also be used ... [more ▼]

PIONIER is a 4-telescope visitor instrument for the VLTI, planned to see its first fringes in 2010. It combines four ATs or four UTs using a pairwise ABCD integrated optics combiner that can also be used in scanning mode. It provides low spectral resolution in H and K band. PIONIER is designed for imaging with a specific emphasis on fast fringe recording to allow closure-phases and visibilities to be precisely measured. In this work we provide the detailed description of the instrument and present its updated status. [less ▲]

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See detailMulti-axial integrated optics solution for POPS, a 2nd-generation VLTI fringe tracker
Tarmoul, Nassima; Hénault, François; Mourard, Denis et al

in Danchi, W. C.; Delplancke, F.; Rajagopal, J. K. (Eds.) Optical and Infrared Interferometry II (2010, July)

POPS (Planar Optical Phase Sensor) is a second-generation fringe tracker for the Very Large Telescope Interferometer (VLTI), intended to simultaneously measure the cophasing and coherencing errors of up ... [more ▼]

POPS (Planar Optical Phase Sensor) is a second-generation fringe tracker for the Very Large Telescope Interferometer (VLTI), intended to simultaneously measure the cophasing and coherencing errors of up to six Unit Telescopes (UT) or Auxiliary Telescopes (AT) in real time. The most promising concepts are probably based on the utilization of Integrated Optics (IO) components, and were the scope of a Phase A study led by Observatoire de Grenoble (LAOG). Herein is described a tentative design built around a multi-axial IO chip whose fringes are dispersed downstream on a detector array, and a Chromatic Phase Diversity algorithm presented in another paper of this conference . We depict the foreseen opto-mechanical, detection and software implementations, and provide numerical results from a realistic simulation model in terms of group and phase delay measurement accuracy and limiting magnitudes in the K band. The ultimate performance of the method is discussed and compared with the original 2[SUP]nd[/SUP] generation VLTI fringe tracker requirements. [less ▲]

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See detailDevelopment of a CELestial Infrared Nuller Experiment (CELINE) for broadband nulling and new single-mode fiber testing
Hanot, Charles ULiege; Riaud, Pierre; Mawet, Dimitri et al

in Danchi, W. C.; Delpancke, F.; Rajagopal, J. K. (Eds.) Optical and Infrared Interferometry II (2010, July)

he small angular distance (<100 mas) and the huge flux ratio (107) between an Earth-like exoplanet in the socalled habitable zone and its host star makes it very difficult to direct image such systems ... [more ▼]

he small angular distance (<100 mas) and the huge flux ratio (107) between an Earth-like exoplanet in the socalled habitable zone and its host star makes it very difficult to direct image such systems. Nulling interferometry consists of a very powerful technique that combines destructively the light from two or more collectors to dim the starlight and to reveal faint companions in its vicinity. We have developed a new nulling experiment based on the fiber nuller principle. This fully symmetric reflective nulling bench aims at testing broadband nulling in both H and K bands as well as characterizing photonic fibers for modal filtering. We present in this paper the design, the development as well as preliminary results of the experiment. [less ▲]

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See detailCompared sensitivities of VLT, JWST and ELT for direct exoplanet detection in nearby stellar moving groups
Hanot, Charles ULiege; Absil, Olivier ULiege; Surdej, Jean ULiege et al

in Oschmann, J.; Clampin, M.; MacEwen, H. (Eds.) Space Telescopes and Instrumentation 2010: Optical, Infrared, and Millimeter Wave (2010, July)

In the context of exoplanet detection, a large majority of the 400 detected exoplanets have been found by indirect methods. Today, progress in the field of high contrast and angular resolution imaging has ... [more ▼]

In the context of exoplanet detection, a large majority of the 400 detected exoplanets have been found by indirect methods. Today, progress in the field of high contrast and angular resolution imaging has allowed direct images of several exoplanetary systems to be taken (cf. HR 8799, Fomalhaut and β Pic).[SUP]1-4[/SUP] In the near future, several new instruments are going to dramatically improve our sensitivity to exoplanet detection. Among these, SPHERE (Spectro Polarimetric High contrast Exoplanet REsearch) at the VLT, MIRI (Mid Infra-Red Instrument) onboard JWST and EPICS at the ELT will be equipped with coronagraphs to reveal faint objects in the vicinity of nearby stars. We made use of the Lyon group (COND) evolutionary models of young (sub-)stellar objects and exoplanets to compare the sensitivities of these different instruments using their estimated coronagraphic profiles. From this comparison, we present a catalogue of targets which are particularly well suited for the different instruments. [less ▲]

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See detailGlobal Analysis of Firing Maps
Mauroy, Alexandre ULiege; Hendrickx, Julien; Megretski, Alexandre et al

in Proceedings of the 19th International Symposium on Mathematical Theory of Networks and Systems (2010, July)

In this paper, we study the behavior of pulse-coupled integrate-and-fire oscillators. Each oscillator is characterized by a state evolving between two threshold values. As the state reaches the upper ... [more ▼]

In this paper, we study the behavior of pulse-coupled integrate-and-fire oscillators. Each oscillator is characterized by a state evolving between two threshold values. As the state reaches the upper threshold, it is reset to the lower threshold and emits a pulse which increments by a constant value the state of every other oscillator. The behavior of the system is described by the so-called firing map: depending on the stability of the firing map, an important dichotomy characterizes the behavior of the oscillators (synchronization or clustering). The firing map is the composition of a linear map with a scalar nonlinearity. After briefly discussing the case of the scalar firing map (corresponding to two oscillators), the stability analysis is extended to the general n-dimensional firing map (for n +1 oscillators). Different models are considered (leaky oscillators, quadratic oscillators,...), with a particular emphasis on the persistence of the dichotomy in higher dimensions. [less ▲]

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See detailMassive binaries as seen with GAIA
Palate, Matthieu ULiege; Rauw, Grégor ULiege; Gosset, Eric ULiege et al

Poster (2010, July)

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See detailImprovements and validation of mid-infrared predictions of milk fatty acid
Soyeurt, Hélène ULiege; McParland, Sinead; Donagh, Berry et al

Conference (2010, July)

The development of mid-infrared equations to predict the milk fatty acid (FA) content of milk allows prompt analysis of large numbers of samples. The first aim was to improve these predictions by ... [more ▼]

The development of mid-infrared equations to predict the milk fatty acid (FA) content of milk allows prompt analysis of large numbers of samples. The first aim was to improve these predictions by comparing 6 statistical approaches. The second one was to validate the new equations using an independent sample set. The calibration set contained 239 spectrally different Belgian milk samples collected for over 2 years from several cows and breeds. FA were quantified by gas chromatography (GC). Statistical approaches tested were 1) partial least squares regression (PLS), 2) PLS and first derivative, 3) PLS and repeatability file (RF), 4) PLS, first derivative and RF, 5) PLS, second derivative, and 6) PLS, second derivative and RF. This last file contained spectra obtained from the same samples using 5 spectrometers. Cross-validation (CV) used 20 groups from the calibration set. Methods were compared using the ratio of the standard deviation of GC values to the standard error of CV (RPD). An external validation permitted a second comparison and was done using 362 samples collected for one year from multiple breeds and cows in Belgium, Ireland, and Scotland. Different RPD values were obtained by the 6 methods. Generally the equations developed using method 4 gave better results suggesting the adaptation of the methodology to the studied FA. It confirms by the obtained validation coefficients of determination. Highest values were observed for the equations with the highest RPD values except for C18:0. The ability to predict FA using method 4 gave superior results to those shown in previous publications. [less ▲]

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See detailExercise pulmonary hypertension in asymptomatic degenerative mitral regurgitation
Magne, Julien ULiege; Lancellotti, Patrizio ULiege; Pierard, Luc ULiege

in Circulation (2010), 122(1), 33-41

BACKGROUND: Current guidelines recommend mitral valve surgery for asymptomatic patients with severe degenerative mitral regurgitation and preserved left ventricular systolic function when exercise ... [more ▼]

BACKGROUND: Current guidelines recommend mitral valve surgery for asymptomatic patients with severe degenerative mitral regurgitation and preserved left ventricular systolic function when exercise pulmonary hypertension (PHT) is present. However, the determinants of exercise PHT have not been evaluated. The aim of this study was to identify the echocardiographic predictors of exercise PHT and the impact on symptoms. <br /> <br />METHODS AND RESULTS: Comprehensive resting and exercise transthoracic echocardiography was performed in 78 consecutive patients (age, 61+/-13 years; 56% men) with at least moderate degenerative mitral regurgitation (effective regurgitant orifice area =43+/-20 mm(2); regurgitant volume =71+/-27 mL). Exercise PHT was defined as a systolic pulmonary arterial pressure (SPAP) >60 mm Hg. Exercise PHT was present in 46% patients. In multivariable analysis, exercise effective regurgitant orifice was an independent determinant of exercise SPAP (P<0.0001) and exercise PHT (P=0.002). Resting PHT and exercise PHT were associated with markedly reduced 2-year symptom-free survival (36+/-14% versus 59+/-7%, P=0.04; 35+/-8% versus 75+/-7%, P<0.0001). After adjustment, although the impact of resting PHT was no longer significant, exercise PHT was identified as an independent predictor of the occurrence of symptoms (hazard ratio=3.4; P=0.002). Receiver-operating characteristics curves revealed that exercise PHT (SPAP >56 mm Hg) was more accurate than resting PHT (SPAP >36 mm Hg) in predicting the occurrence of symptoms during follow-up (P=0.032). <br /> <br />CONCLUSIONS: Exercise PHT is frequent in patients with asymptomatic degenerative mitral regurgitation. Exercise mitral regurgitation severity is a strong independent predictor of both exercise SPAP and exercise PHT. Exercise PHT is associated with markedly low 2-year symptom-free survival, emphasizing the use of exercise echocardiography. An exercise SPAP >56 mm Hg accurately predicts the occurrence of symptoms. [less ▲]

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See detailLes prényltransférases et leurs rôles biologiques chez les pucerons
Vandermoten, Sophie ULiege; Cusson, Michel; Haubruge, Eric ULiege et al

Conference (2010, July)

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See detailImpact of Oil Solubility and Refrigerant Flashing on the Performance of Transcritical CO2 Vapor Compression Systems with Oil Flooding and Regeneration
Bell, Ian ULiege; Groll, Eckhard; Braun, James et al

in International Refrigeration and Air Conditioning Conference at Purdue, July 12-15, 2010 (2010, July)

Flooding the compressor of a vapor compression system with oil can allow for a more isothermal compression process. This can lead to significant improvements in performance, particularly when combined ... [more ▼]

Flooding the compressor of a vapor compression system with oil can allow for a more isothermal compression process. This can lead to significant improvements in performance, particularly when combined with a regenerative heat exchanger. For CO2 cycles with supercritical heat rejection, the superheat horn and throttle are major sources of irreversibility. The combination of flooding and regeneration attacks both of these losses with a relatively small impact on system costs. The improvement in system COP can be over 20% for sink and source temperatures of 30°C and -30°C, respectively, with an optimized oil mass fraction and oils that have low refrigerant solubility. However, when some amount of refrigerant is solved in the oil, the cooling capacity is decreased. At a refrigerant solubility of 20% by mass in the oil for fixed oil mass fraction, there is no improvement in system COP compared to the baseline system. [less ▲]

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See detailUn romanzo di Mussolini
Curreri, Luciano ULiege

in L'Indice dei Libri del Mese (2010), 7/8

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See detailUpdate on Scroll Compressor Chamber Geometry
Bell, Ian ULiege; Groll, Eckhard; Braun, James et al

in International Compressor Engineering Conference at Purdue (2010, July)

The geometry of the scroll compressor determines the efficiency of the scroll compressor and controls all elements of its operation. It is therefore critical to be able to accurately model the volumes of ... [more ▼]

The geometry of the scroll compressor determines the efficiency of the scroll compressor and controls all elements of its operation. It is therefore critical to be able to accurately model the volumes of the compressor over the course of a revolution. This paper proposes a novel quasi-analytic formulation of the suction, compression and discharge chambers based on a change of variables from involute angle to polar integration angle. This solution has been compared against a reference polygon solution, and for the suction chamber this solution agrees to within 0.02%. The solutions for the compression and discharge chamber volumes are analytic and incur a negligible penalty to overhead of a detailed compressor model. In addition, the general nature of the solution presented allows for multiple compression chambers and more complex discharge geometry. [less ▲]

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See detailAdaptive Wide-Area Closed-Loop Undervoltage Load Shedding Using Synchronized Measurements
Glavic, Mevludin; Van Cutsem, Thierry ULiege

in Proceedings of IEEE PES 2010 General Meeting (2010, July)

This paper proposes an emergency load shedding scheme aimed at stopping a developing voltage instability before system disruption. The proposed scheme has a wide-area view of the system, adapts itself to ... [more ▼]

This paper proposes an emergency load shedding scheme aimed at stopping a developing voltage instability before system disruption. The proposed scheme has a wide-area view of the system, adapts itself to the emergency situation to be handled, and works in closed-loop. It relies on the detection of voltage instability from synchronized measurements recently proposed by the authors. It inherits the assumptions of this detection method (availability of a rich phasor measurement set and communication infrastructure). The method is adaptive in so far as the voltage thresholds used by this undervoltage load shedding scheme are determined from the measurements of the system evolution itself, and the curtailed power is adjusted to the severity of the situation. The features of the proposed scheme are illustrated on a small but realistic system. [less ▲]

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See detailLes enseignants en éducation physique wallons connaissent-ils le socioconstructivisme et pensent-ils l'utiliser?
Cloes, Marc ULiege; Berwart, Gilles; Frédéric, Olivier

in e Journal de la Recherche sur l'Intervention en Education Physique et Sport (2010), 21

In France and in the Anglo-Saxon countries, socioconstructivist approach tends currently to be increasingly used by physical education teachers. However, it seems that their colleagues from the Wallonia ... [more ▼]

In France and in the Anglo-Saxon countries, socioconstructivist approach tends currently to be increasingly used by physical education teachers. However, it seems that their colleagues from the Wallonia-Brussels Community are much more traditional in the sense that they focus largely on "technicist” approaches. The purpose of this study was to determine to what extent they know the principles of this new approach and consider that they apply it in their classes. We collected 123 questionnaires completed online by secondary school level physical education teachers, contacted by using the "snowball" sampling technique. Despite the increase of the socioconstructivism literature, the development of specific courses focusing on it in physical education teacher education programs or the organization of specific inservice activities, 4 out of 10 teachers had no idea about what this concept means. The answers given by the subjects when they had to define the concept or to describe teaching situations in which they applied it confirmed this finding. Our study illustrates the difficulties faced by practitioners when it comes to update their knowledge on the one hand, to incorporate new concepts into their practice, on the other hand. The findings emphasize the gap between the development of educational theories and their appropriation on the field. [less ▲]

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See detailHeterogeneity of residuals variances of milk fatty acids in dairy cattle
Arnould, Valérie ULiege; Soyeurt, Hélène ULiege; Vanderick, Sylvie ULiege et al

Conference (2010, July)

Routine genetic evaluation for milk fatty acids is under development in the Walloon Region of Belgium. The objective of this study was to test the heterogeneity of residual variances and therefore ... [more ▼]

Routine genetic evaluation for milk fatty acids is under development in the Walloon Region of Belgium. The objective of this study was to test the heterogeneity of residual variances and therefore indirectly the potential need to adjust for this heterogeneity if it exists. The residuals were computed as the difference between the observed and the estimated values using a multi-trait random regression test-day model, similar to the Walloon routine model, used for first lactation only milk yield, quantities and percentages of protein (PROT) and fat (FAT), content of saturated fatty acids in milk (g/100g of milk, SAT) and, content of mono-unsaturated fatty acids in milk (g/100g of milk, MONO). Residuals were considered homogeneous inside strata defined, among others, by weeks of lactation, by days in milk and by calendar months of test date. About 6,687,000 records were available for milk yield and for FAT and PROT parameters. For SAT and for MONO, about 184,000 records were available in this database. Means of residuals were stable and close to zero for all traits. Variances were more variable for MONO and SAT than for milk yield, for example. Daily and weekly variances tended to decrease at the end of the lactation (50%). When the variances were computed by month of test date, some variations were observed and some periods of year were more marked. In conclusion, the observed residual variances were less stable for MONO and SAT. We can conclude that introduction for heterogeneous residual variance is more important for the new traits (MONO, SAT) than it was for the old, traditional ones. [less ▲]

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See detailHeterogeneity of residuals variances of milk fatty acids in dairy cattle
Arnould, Valérie ULiege; Soyeurt, Hélène ULiege; Vanderick, Sylvie ULiege et al

in Journal of Dairy Science (2010, July), 88(E-Suppl. 2), 744

Routine genetic evaluation for milk fatty acids is under development in the Walloon Region of Belgium. The objective of this study was to test the heterogeneity of residual variances and therefore ... [more ▼]

Routine genetic evaluation for milk fatty acids is under development in the Walloon Region of Belgium. The objective of this study was to test the heterogeneity of residual variances and therefore indirectly the potential need to adjust for this heterogeneity if it exists. The residuals were computed as the difference between the observed and the estimated values using a multi-trait random regression test-day model, similar to the Walloon routine model, used for first lactation only milk yield, quantities and percentages of protein (PROT) and fat (FAT), content of saturated fatty acids in milk (g/100g of milk, SAT) and, content of mono-unsaturated fatty acids in milk (g/100g of milk, MONO). Residuals were considered homogeneous inside strata defined, among others, by weeks of lactation, by days in milk and by calendar months of test date. About 6,687,000 records were available for milk yield and for FAT and PROT parameters. For SAT and for MONO, about 184,000 records were available in this database. Means of residuals were stable and close to zero for all traits. Variances were more variable for MONO and SAT than for milk yield, for example. Daily and weekly variances tended to decrease at the end of the lactation (50%). When the variances were computed by month of test date, some variations were observed and some periods of year were more marked. In conclusion, the observed residual variances were less stable for MONO and SAT. We can conclude that introduction for heterogeneous residual variance is more important for the new traits (MONO, SAT) than it was for the old, traditional ones. [less ▲]

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See detailMixed-integer sets from two rows of two adjacent simplex bases
Andersen, Kent; Louveaux, Quentin ULiege; Weismantel, Robert

in Mathematical Programming (2010), 124(1-2), 455-480

In 2007 we studied a mixed-integer set arising from two rows of a simplex tableau. We showed that facets of such a set can be obtained from lattice point free triangles and quadrilaterals associated with ... [more ▼]

In 2007 we studied a mixed-integer set arising from two rows of a simplex tableau. We showed that facets of such a set can be obtained from lattice point free triangles and quadrilaterals associated with either three or four variables. In this paper we generalize our findings and show that, when upper bounds on the non-basic variables are also considered, further classes of facets arise that cannot be obtained from triangles and quadrilaterals. Specifically, when exactly one upper bound on a non-basic variable is intro- duced, stronger inequalities that can be derived from pentagons involving up to six variables also appear. [less ▲]

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