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See detailAnalysis of luminosity distributions and shape parameters of strong gravitational lensing elliptical galaxies
Biernaux, Judith ULiege; Magain, Pierre ULiege; Sluse, Dominique ULiege et al

in Astronomy and Astrophysics (2016), 585

Context. The luminosity profiles of galaxies acting as strong gravitational lenses can be tricky to study. Indeed, strong gravitational lensing images display several lensed components, both point-like ... [more ▼]

Context. The luminosity profiles of galaxies acting as strong gravitational lenses can be tricky to study. Indeed, strong gravitational lensing images display several lensed components, both point-like and diffuse, around the lensing galaxy. Those objects restrain the study of the galaxy luminosity to its inner parts. Therefore, the usual fitting methods perform rather badly on such images. Previous studies of strong lenses luminosity profiles using such codes and various PSF-determining methods have resulted in somewhat discrepant results. Aims. The present work aims at investigating the causes of those discrepancies, as well as at designing more robust techniques to study the morphology of early-type lensing galaxies, with the ability to subtract lensed signal from their luminosity profiles. Methods. Each shape parameter, namely, the position angle, ellipticity and half-light radius of the galaxy, are determined as independently from each other as possible. The half-light radius measurement method is based on the computation of isophotes. Its robustness regarding various specific aspects of gravitational lensing image processing is analysed and tested versus that of a widely used fitting code, GALFIT. Those techniques are then applied on a sample of systems from the CASTLES database. Results. Simulations show that, when restricted to small, inner parts of the lensing galaxy, the technique presented here is more robust than GALFIT. It gives unbiased results, while GALFIT leads to an overestimation of the half-light radius that can reach about 10%, depending, among others, on the SNR. It is therefore better-suited than GALFIT for gravitational lensing images. It is also able to study lensing galaxies that are not much larger than the PSF, as opposed to GALFIT. New values for the half-light radius of the objects in our sample are presented and compared to previous works. [less ▲]

Detailed reference viewed: 46 (20 ULiège)
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See detailAnalysis of mainstream tobacco smoke by SPME-GC×GC-TOFMS
Brokl, Michal ULiege; Bishop, L; Wright, C et al

Poster (2013, May)

Detailed reference viewed: 46 (3 ULiège)
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See detailAnalysis of mainstream tobacco smoke particulate phase using comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry
Brokl, Michal ULiege; Bishop, L; Wright, C et al

in Journal of Separation Science (2013), 31

In tobacco research, the comparison of different tobacco blends as well as the puffdependent <br />behaviour of cigarettes is a matter of particular interest. For the investigation <br />of smoke ... [more ▼]

In tobacco research, the comparison of different tobacco blends as well as the puffdependent <br />behaviour of cigarettes is a matter of particular interest. For the investigation <br />of smoke characteristics, GC6GC offers different ways for data analysis, <br />namely, compound target analysis, automated peak-based compound classification <br />and comprehensive pixel-based data analysis. This study will show the application <br />as well as the pros and cons of these types of data analysis for very complex matrices <br />like cigarette particulate matter. In addition, new aspects about the recently discovered <br />puff-dependent behaviour of compounds in cigarette smoke will be presented. <br />Automated peak-based compound classification including mass spectrometric pattern <br />recognition is used for the classification of tobacco particulate matter samples <br />and the puff-dependent investigation of different compound classes. This compound <br />group specific analysis is further reinforced by applying an even more comprehensive <br />pixel-based analysis. This kind of analysis is used to generate fingerprints of <br />different types of cigarettes. The combination of fast feature reduction methods like <br />analysis of variance (ANOVA) and t-test with multivariate feature transformation <br />methods like partial least squares discriminate analysis (PLSDA) for feature selection <br />provides a powerful tool for a detailed inspection of different types of cigarettes. [less ▲]

Detailed reference viewed: 74 (16 ULiège)
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See detailAnalysis of Martian nightglow and aurora
Stiepen, Arnaud ULiege

Conference (2015, March)

Detailed reference viewed: 26 (2 ULiège)
See detailAnalysis of mass movements affecting the region of Constantine
Draidia, Salah ULiege; Havenith, Hans-Balder ULiege; Benabbas, C.

in EGU General Assembly Conference Abstracts (2014)

Abstract: Mass movements are a very frequent phenomenon in the North-Eastern Algeria, causing a lot of damages among the population and on the infrastructures and representing the most important geohazard ... [more ▼]

Abstract: Mass movements are a very frequent phenomenon in the North-Eastern Algeria, causing a lot of damages among the population and on the infrastructures and representing the most important geohazard. This paper presents some results of the analysis of slope instabilities in many places in the region and especially along the East-West highway. The work show many types of failures characterized by a high degree of heterogeneity. It is clear that the landslides in this area are very complex, in the most cases a combination of ... [less ▲]

Detailed reference viewed: 17 (1 ULiège)
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See detailAnalysis of MERCATOR data - Part I: variable B stars
De Cat, P.; Briquet, Maryline ULiege; Aerts, C. et al

in Communications in Asteroseismology (2006), 147

We re-classified 31 variable B stars which were observed more than 50 times in the Geneva photometric system with the p7 photometer attached to the MERCATOR telescope (La Palma) during its first 3 years ... [more ▼]

We re-classified 31 variable B stars which were observed more than 50 times in the Geneva photometric system with the p7 photometer attached to the MERCATOR telescope (La Palma) during its first 3 years of scientific observations. HD 89688 is a possible beta Cephei/slowly pulsating B star hybrid and the main mode of the COROT target HD 180642 shows non-linear effects. The Maia candidates are re-classified as either ellipsoidal variables or spotted stars. Although the mode identification is still ongoing, all the well-identified modes so far have l <= 2. [less ▲]

Detailed reference viewed: 15 (2 ULiège)
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See detailAnalysis of Migration in a Multi-Risk Context: Case of Bujumbura/Burundi
Nibigira, Léonidas ULiege; Ozer, Pierre ULiege; Havenith, Hans-Balder ULiege

in MAIER, ROBIN; REVELL, MARK (Eds.) THE AMERICAN ASSOCIATION OF GEOGRAPHERS, 2017 Annual Meeting, April 5 - 9, 2017 Boston, Massachusetts / PROGRAM (2017, April 08)

Human mobility affects land use and human density distribution. Unfortunately, this rarely takes into account the real and potential changes induced by hazards on the natural systems. Thus, migration and ... [more ▼]

Human mobility affects land use and human density distribution. Unfortunately, this rarely takes into account the real and potential changes induced by hazards on the natural systems. Thus, migration and natural hazards should be constantly analyzed through cross-sectional and global studies to reduce disastrous consequences resulting from their mutual interactions. In a multi-risk and demographic sprawl context, the study focused on the cross-analysis of human density and natural hazards in Bujumbura. The results show that migration of people should ideally be guided by knowledge of the area's sensitivity to natural hazards, taking into account other parameters such as hazards susceptibility maps and production opportunities. While the migration of people toward overcrowded centers constitutes a big challenge, it is an important asset when it concerns areas in need of manpower. It also allows the balance in relieving saturated areas, reducing human pressure on the environment. Therefore, there is a need that policymakers comply with those aspects, finding the right balance for a better situation. [less ▲]

Detailed reference viewed: 95 (20 ULiège)
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See detailAnalysis of Minimal In-Flight Oxygen Collection Cycle for Two Stage Launchers
Bizzarri, Didier; Heyen, Georges ULiege; Hendrick, Patrick et al

in 14th AIAA/AHI International Space Planes and Hypersonic Systems and Technologies Conference (2006, November)

Detailed reference viewed: 30 (2 ULiège)
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See detailAn analysis of mixed integer linear sets based on lattice point free convex sets
Andersen, Kent; Louveaux, Quentin ULiege; Weismantel, Robert

in Mathematics of Operations Research (2010), 35(1), 233-256

The set obtained by adding all cuts whose validity follows from a maximal lattice free polyhedron with max-facet-width at most w is called the w th split closure. We show the w th split closure is a ... [more ▼]

The set obtained by adding all cuts whose validity follows from a maximal lattice free polyhedron with max-facet-width at most w is called the w th split closure. We show the w th split closure is a polyhedron. This generalizes a previous result showing this to be true when w = 1. We also consider the design of finite cutting plane proofs for the validity of an inequality. Given a measure of “size” of a maximal lattice free polyhedron, a natural question is how large a size s of a maximal lattice free polyhedron is required to design a finite cutting plane proof for the validity of an inequality. We characterize s based on the faces of the linear relaxation of the mixed integer linear set. [less ▲]

Detailed reference viewed: 99 (17 ULiège)
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See detailAnalysis of models of redistribution of direct support to farm income in the European Union
Terrones Gavira, François ULiege; Dellanoy, Sylvain; Closset, Marie-France et al

in Vîntu, Vasile (Ed.) Proceedings of the 55th International Scientific Conference "100 years of Iasi higher education in agronomy" : book of abstracts (2012)

Detailed reference viewed: 61 (12 ULiège)
See detailAnalysis of mortality and morbidity data
Brichant, Jean-François ULiege

Conference (2010, January 08)

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See detailAnalysis of MRI stomach scans using differential equations
Frasso, Gianluca ULiege; Lambert, Philippe ULiege; Eilers, Paul H.C.

Poster (2014, September)

Differential equations (DE) are commonly used to describe dynamic systems evolving in one (e.g. time) or more dimensions (e.g. space and time). In real applications the parameters defining the theoretical ... [more ▼]

Differential equations (DE) are commonly used to describe dynamic systems evolving in one (e.g. time) or more dimensions (e.g. space and time). In real applications the parameters defining the theoretical model describing the phenomenon under consideration are often unknown and need to be estimated from the available measurements. This estimation task has been extensively discussed in the statistical literature and probably the most popular procedures are those relying on nonlinear least squares (Bielger et al, 1986). These approaches are computationally intensive and often poorly suited for statistical inference. An attractive alternative is represented by the penalized smoothing procedure introduced by Ramsay et al. (2007). This approach can be viewed as a generalization of the L-spline framework (see Welham et al., 2006 among others) where the flexibility of a high dimensional B-spline expansion of the state function is counterbalanced by a penalty term defining the (set of) differential equation(s) synthesizing the dynamics under investigation. The fidelity of the extracted signal to the hypothesized model is then tuned by a “DE-compliance” parameter to be extracted form the data too. This approach works reasonably well both with linear and nonlinear differential models but, in the latter case, due to the implicit link between the vector of unknown DE parameters and the spline coefficients, the computational burden tends to increase and the optimization of the compliance parameter can be demanding. To overcome these drawbacks we adopt the quasilinearized (QL) ODE-P-spline approach proposed by Frasso et al. (2014). The quasilinearization (Bellman and Kalaba, 1965) step greatly reduces the computational cost of the estimation procedure making the penalty term a second order polynomial function of the DE parameters. As motivating example we present the results of a QL-ODE-P-spline analysis of a set of MRI scans describing stomach contractions during digestion. For illustrative purposes we analyze the measurements related to a single slice of the stomach. Finally, we conclude with a discussion of the possible further extensions of the presented methodology. [less ▲]

Detailed reference viewed: 29 (5 ULiège)
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See detailAnalysis of Ocean in Situ Observations and Web - Based Visualization: From Individual Measurements to an Integrated View
Barth, Alexander ULiege; Watelet, Sylvain ULiege; Troupin, Charles et al

in Diviacco, Paolo; Leadbetter, Adam; Glaves, Helen (Eds.) Oceanographic and Marine Cross-Domain Data Management for Sustainable Development (2016)

The sparsity of observations poses a challenge common to various ocean disciplines. Even for physical parameters where the spatial and temporal coverage is higher, current observational networks ... [more ▼]

The sparsity of observations poses a challenge common to various ocean disciplines. Even for physical parameters where the spatial and temporal coverage is higher, current observational networks undersample a broad spectrum of scales. This situation is generally more severe for chemical and biological parameters because such sensors are less widely deployed. The present chapter describes the analysis tool DIVA (Data-Interpolating Variational Analysis) which is designed to generate gridded fields from in situ observations. DIVA has been applied to various physical (temperature and salinity), chemical (concentration of nitrate, nitrite and phosphate) and biological parameters (abundance of a species). The chapter also shows the technologies used to visualize the gridded fields. Visualization of analyses from in situ observations provide a unique set of challenges since the accuracy of the analysed field is not spatially uniform as it strongly depends on the location of the observations. In addition, an adequate treatment of the depth and time dimensions is essential. [less ▲]

Detailed reference viewed: 119 (13 ULiège)
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See detailAnalysis of ocean in situ observations and web-based visualization
Barth, Alexander ULiege; Watelet, Sylvain ULiege; Troupin, Charles ULiege et al

Conference (2016)

The sparsity of observations poses a challenge common to various ocean science disciplines. Even for physical parameters where the spatial and temporal coverage is higher, current observational networks ... [more ▼]

The sparsity of observations poses a challenge common to various ocean science disciplines. Even for physical parameters where the spatial and temporal coverage is higher, current observational networks undersample a broad spectrum of scales. The situation is generally more severe for chemical and biological parameters because related sensors are less widely deployed. The analysis tool DIVA (Data-Interpolating Variational Analysis) is designed to generate gridded fields from in situ observations. DIVA has been applied to various physical (temperature and salinity), chemical (concentration of nitrate, nitrite and phosphate) and biological parameters (abundance of a species) in the context of different European projects (SeaDataNet, EMODnet Chemistry and EMODnet Biology). We show the technologies used to visualize the gridded fields based on the Web Map Services standard. Visualization of analyses from in situ observations provides a unique set of challenges since the accuracy of the analysed field is not spatially uniform as it strongly depends on the observations location. In addition, an adequate handling of depth and time dimensions is essential. Beside visualizing the gridded fields, access is also given to the underlying observations. It is thus also possible to view more detailed information about the variability of the observations. The in situ observation visualization service allows one to display vertical profiles and time series and it is built upon OGC standards (the Web Feature Service and Web Processing Services) and following recommendation from the INSPIRE directive. [less ▲]

Detailed reference viewed: 40 (8 ULiège)
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See detailAnalysis of Ocean In Situ Observations and Web-Based Visualization: From Individual Measurements to an Integrated View
Barth, Alexander ULiege; Watelet, Sylvain ULiege; Troupin, Charles ULiege et al

in Paolo, Diviacco; Leadbetter, Adam; Glaves, Helen (Eds.) Oceanographic and Marine Cross-Domain Data Management for Sustainable Development (2017)

Detailed reference viewed: 25 (1 ULiège)