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See detailProper orthogonal decomposition for model updating of non-linear mechanical systems
Lenaerts, V.; Kerschen, Gaëtan ULg; Golinval, Jean-Claude ULg

in Mechanical Systems & Signal Processing (2001), 15(1)

Proper orthogonal decomposition (POD), also known as Karhunen}Loeve (K}L) decomposition, is emerging as a useful experimental tool in dynamics and vibrations. The POD is a means of extracting spatial ... [more ▼]

Proper orthogonal decomposition (POD), also known as Karhunen}Loeve (K}L) decomposition, is emerging as a useful experimental tool in dynamics and vibrations. The POD is a means of extracting spatial information from a set of time-series data available on a domain. The use of (K}L) transform is of great help in non-linear settings where traditional linear techniques such as modal-testing and power-spectrum analyses cannot be applied. These decomposition can be used as an orthogonal basis for e$cient representation of the ensemble. The POM have been interpreted mainly as empirical system modes and the application of POD to measured displacements of a discrete structure with a known mass matrix leads to an estimation of the normal modes. We investigate the use of the proper orthogonal modes of displacements for the identi"cation of parameters of non-linear dynamical structures with an optimisation procedure based on the di!erence between the experimental and simulated POM. A numerical example of a beam with a local non-linear component will illustrate the method. (C) 2001 Academic Press [less ▲]

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See detailProper Orthogonal Decomposition for Nonlinear Radiative Heat Transfer Problems
Hickey, D.; Masset, Luc ULg; Kerschen, Gaëtan ULg et al

in Proceedings of the ASME International Design Engineering Technical Conferences (2011)

Analysing large scale, nonlinear, multiphysical, dynamical structures, by using mathematical modelling and simulation, e.g. Finite Element Modelling (FEM), can be computationally very expensive ... [more ▼]

Analysing large scale, nonlinear, multiphysical, dynamical structures, by using mathematical modelling and simulation, e.g. Finite Element Modelling (FEM), can be computationally very expensive, especially if the number of degrees-of-freedom is high. This paper develops modal reduction techniques for such nonlinear multiphysical systems. The paper focuses on Proper Orthogonal Decomposition (POD), a multivariate statistical method that obtains a compact representation of a data set by reducing a large number of interdependent variables to a much smaller number of uncorrelated variables. A fully coupled, thermomechanical model consisting of a multilayered, cantilever beam is described and analysed. This linear benchmark is then extended by adding nonlinear radiative heat exchanges between the beam and an enclosing box. The radiative view factors, present in the equations governing the heat fluxes between beam and box elements, are obtained with a raytracing method. A reduction procedure is proposed for this fully coupled nonlinear, multiphysical, thermomechanical system. Two alternative approaches to the reduction are investigated, a monolithic approach incorporating a scaling factor to the equations, and a partitioned approach that treats the individual physical modes separately. The paper builds on previous work presented previously by the authors. The results are given for the RMS error between either approach and the original, full solution. [less ▲]

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See detailProper Orthogonal Decomposition of Unsteady Aerodynamic Flows
Andrianne, Thomas ULg; Ligot, Jerome; Dimitriadis, Grigorios ULg

Report (2009)

This work constitutes the final report for a project funded by the Fonds de la Recherche Scientifique. The objective of the project was to acquire and install Par- tical Image Velocimetry (PIV) hardware ... [more ▼]

This work constitutes the final report for a project funded by the Fonds de la Recherche Scientifique. The objective of the project was to acquire and install Par- tical Image Velocimetry (PIV) hardware in the University of Liege Wind Tunnel facility in order to carry out the Proper Orthogonal Decomposition (POD) of un- steady aerodynamic flows. The characteristics and installation of the PIV system are described in the present report. Furthermore, the application of POD analysis to three different visualized flow cases is detailed. The flow cases were: flow be- hind a circular cylinder and separated flow over a rectangular wing. In all cases, emphasis was given to the combination of unsteadiness caused by both boundary layer separation and movement of the wind tunnel model. It is shown that the de- composition of flowfields that combine these two sources of unsteadiness is possible and informative. [less ▲]

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See detailProper Orthogonal modes for the characterisation of nonlinear dynamic systems
Kerschen, Gaëtan ULg; Lenaerts, Vincent; Golinval, Jean-Claude ULg et al

in Euromech Colloquim on Nonlinear Modes of Vibrating Systems, Frejus, 2004 (2004)

Modal analysis is extensively used for the analysis and design of structures. However, a major concern for structural dynamicists is that its validity is limited to systems showing a linear behaviour. New ... [more ▼]

Modal analysis is extensively used for the analysis and design of structures. However, a major concern for structural dynamicists is that its validity is limited to systems showing a linear behaviour. New developments have thus been proposed in order to tackle nonlinear systems among which the theory based on the nonlinear normal modes is indubitably the most appealing. In this study, a different approach is adopted and the modes extracted from the proper orthogonal decomposition are considered for the characterization of nonlinear systems. [less ▲]

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See detailProper-motion binaries in the Hipparcos catalogue. Comparison with radial velocity data
Frankowski, A.; Jancart, Sylvie ULg; Jorissen, A.

in Astronomy and Astrophysics (2007), 464

Context: This paper is the last in a series devoted to the analysis of the binary content of the Hipparcos Catalogue. <BR />Aims: The comparison of the proper motions constructed from positions spanning a ... [more ▼]

Context: This paper is the last in a series devoted to the analysis of the binary content of the Hipparcos Catalogue. <BR />Aims: The comparison of the proper motions constructed from positions spanning a short (Hipparcos) or long time (Tycho-2) makes it possible to uncover binaries with periods of the order of or somewhat larger than the short time span (in this case, the 3 yr duration of the Hipparcos mission), since the unrecognised orbital motion will then add to the proper motion. <BR />Methods: A list of candidate proper motion binaries is constructed from a carefully designed χ[SUP]2[/SUP] test evaluating the statistical significance of the difference between the Tycho-2 and Hipparcos proper motions for 103 134 stars in common between the two catalogues (excluding components of visual systems). Since similar lists of proper-motion binaries have already been constructed, the present paper focuses on the evaluation of the detection efficiency of proper-motion binaries, using different kinds of control data (mostly radial velocities). The detection rate for entries from the Ninth Catalogue of Spectroscopic Binary Orbits (S_B^9) is evaluated, as well as for stars like barium stars, which are known to be all binaries, and finally for spectroscopic binaries identified from radial velocity data in the Geneva-Copenhagen survey of F and G dwarfs in the solar neighbourhood. <BR />Results: Proper motion binaries are efficiently detected for systems with parallaxes in excess of ~20 mas, and periods in the range 1000-30 000 d. The shortest periods in this range (1000-2000 d, i.e., once to twice the duration of the Hipparcos mission) may appear only as DMSA/G binaries (accelerated proper motion in the Hipparcos Double and Multiple System Annex). Proper motion binaries detected among S_B[SUP]9[/SUP] systems having periods shorter than about 400 d hint at triple systems, the proper-motion binary involving a component with a longer orbital period. A list of 19 candidate triple systems is provided. Binaries suspected of having low-mass (brown-dwarf-like) companions are listed as well. Among the 37 barium stars with parallaxes larger than 5 mas, only 7 exhibit no evidence for duplicity whatsoever (be it spectroscopic or astrometric). Finally, the fraction of proper-motion binaries shows no significant variation among the various (regular) spectral classes, when due account is taken for the detection biases. Full Table [see full text] is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/464/377 [less ▲]

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See detailPROPERCE. Elegiae. Index verborum, listes de fréquence
Purnelle, Gérald ULg

Book published by Olms Verlag (1997)

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See detailProperties and crystallization of a genetically engineered, water-soluble derivative of penicillin-binding protein 5 of Escherichia coli K12
Ferreira, Luis C; Schwarz, Uli; Keck, Wolfgang et al

in European Journal of Biochemistry (1988), 171(1-2), 11-16

Derivatives of the Escherichia coli penicillin-binding protein 5 (PBP5) with truncated carboxyl terminals were obtained by altering the carboxyl-coding end of the dacA gene. After cloning the modified ... [more ▼]

Derivatives of the Escherichia coli penicillin-binding protein 5 (PBP5) with truncated carboxyl terminals were obtained by altering the carboxyl-coding end of the dacA gene. After cloning the modified dacA gene into a runaway-replication-control plasmid, one clone that overproduced and excreted the desired protein into the periplasm was used as a source for the isolation of a water-soluble PBP5 (i.e. PBP5S). In PBP5S the carboxyl-terminal 21-amino-acid region of the wild-type protein was replaced by a short 9-amino-acid segment. Milligram amounts of PBP5S were purified by penicillin affinity chromatography in the absence of detergents or of chaotropic agents. PBP5S was stable and possessed DD-carboxypeptidase activity without added Triton X-100. Upon reaction with [14C]benzylpenicillin it was converted into a rather short-lived acyl-enzyme complex, as observed with PBP5. Both PBP5 and PBP5S were crystallized. In contrast to PBP5, PBP5S yielded enzymatically active, well-formed prismatic crystals suitable for X-ray analysis. [less ▲]

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See detailProperties and primary structure of a cold-adapted lipase from an Antarctic bacterium
Arpigny, J. L.; Feller, Georges ULg; Gerday, Charles ULg

in Archives Internationales de Physiologie et de Biochimie (1993), 101

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See detailProperties of a class C beta-lactamase from Serratia marcescens.
Joris, Bernard ULg; De Meester, F; Galleni, Moreno ULg et al

in Biochemical Journal (1986), 239(3), 581-6

A beta-lactamase produced by a penicillin-resistant strain of Serratia marcescens was isolated and purified. The kcat. value for benzylpenicillin was about 5% of that observed for the best cephalosporin ... [more ▼]

A beta-lactamase produced by a penicillin-resistant strain of Serratia marcescens was isolated and purified. The kcat. value for benzylpenicillin was about 5% of that observed for the best cephalosporin substrates. However, the low Km of the penam resulted in a high catalytic efficiency (kcat./Km) and the classification of the enzyme as a cephalosporinase might not be completely justified. It also exhibited a low but measurable activity against cefotaxime, cefuroxime, cefoxitin and moxalactam. Substrate-induced inactivation was observed both with a very good (cephalothin) or a very bad (moxalactam) substrate. The active site was labelled by beta-iodopenicillanate. Trypsin digestion produced a 19-residue active-site peptide whose sequence clearly allowed the classification of the enzyme as a class C beta-lactamase. [less ▲]

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See detailProperties of localized, high latitude, dayside aurora
Frey, H. U.; Immel, T. J.; Lu, G. et al

Conference (2003, February 19)

[1] The FUV instrument on the IMAGE spacecraft frequently observes intense ultraviolet (UV) emission from a localized dayside region poleward of the general auroral oval location. One type of these ... [more ▼]

[1] The FUV instrument on the IMAGE spacecraft frequently observes intense ultraviolet (UV) emission from a localized dayside region poleward of the general auroral oval location. One type of these emissions has been described as the signature of direct proton precipitation into the cusp after lobe reconnection during northward interplanetary magnetic field (IMF) and high solar wind dynamic pressure periods [Frey et al., 2002]. Here we describe a completely different type of high latitude aurora, which does not show any signature of precipitating protons. It also occurs during northward IMF conditions however, only during periods of very low solar wind dynamic pressure. It occurs at a much higher geomagnetic latitude than the normal cusp location and only during periods of positive IMF By. The intensity of the UV emission is somewhat anti-correlated with the solar wind dynamic pressure, much in contrast to the cusp emission. The brightness of the localized emission changes rapidly on time scales between 30 and 70 minutes without corresponding changes in solar wind properties. Coincident measurements by the FAST spacecraft verify that this is not the cusp, that ion precipitation is absent in these regions, and that strong precipitation of field-aligned accelerated electrons causes the aurora. We interpret this aurora as the optical signature of electron precipitation in the upward leg of a current system which closes the downward leg of the current system into the cusp in the ionosphere. [less ▲]

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See detailProperties of mixed monolayers of lecithin and spin probe. II Analysis of the molecular organization
Chatelain, P.; Brasseur, Robert ULg; Ruysschaert, J. M. et al

in Journal of Colloid & Interface Science (1979), 72(2), 294-303

This paper seeks to investigate the molecular organization of fatty acid spin label (4-palmitamido-2,2,6,6-tetramethylpiperidine-1-oxyl) and dipalmitoylphosphatidylcholine molecules in monolayer vesicles ... [more ▼]

This paper seeks to investigate the molecular organization of fatty acid spin label (4-palmitamido-2,2,6,6-tetramethylpiperidine-1-oxyl) and dipalmitoylphosphatidylcholine molecules in monolayer vesicles. The molar ratio of the spin probe was varied from 1 to 22% and the corresponding electron spin resonance spectra were measured at 25 and 48°C. These spectra were analysed in terms of the dipole-dipole and exchange interactions occuring between the radicals. From a computer simulation, a quantitative analysis of these interactions could be made. Comparison of these data with theoretical models indicate that above the lipid phase transition, i.e., at 48°C, the membrane is homogeneous and the label molecules diffuse randomly in the lecithin bulk phase (D = 3.8 X 10-8 cm2/sec). At 25°C, the membrane model can be viewed as a mosaic structure composed of spin probe clusters (7.9 X 1011 clusters/cm2). The size of the clusters as well as the minimal mean distance between two cluster edges could be calculated as a function of the spin label molar ratio. These results are used to interpret the observations made in the first paper of this series [Chatelain et ak., J. Colloid Interface Sci. 72, 287 (1979)] concerning the surface viscosity of the mixed monolayer and the kinetics of the enzymatic activity of phospholipase A2. It can be concluded that above a critical spin label concentration (10-15%) the properties of the entire lecithin phase are influenced by the presence of the spin probe clusters. [less ▲]

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See detailProperties of molten Ge chalcogenides: an ab initio molecular dynamics study
Raty, Jean-Yves ULg; Gaspard, Jean-Pierre ULg; Bichara, C.

in Journal of Physics-Condensed Matter (2003), 15(1 Sp. Iss. SI), 167-173

In this study, we perform first-principles molecular dynamics simulations of the eutectic alloy Ge15Te85 at five different densities and temperatures. We obtain structures in agreement with the available ... [more ▼]

In this study, we perform first-principles molecular dynamics simulations of the eutectic alloy Ge15Te85 at five different densities and temperatures. We obtain structures in agreement with the available diffraction data and obtain a new view of the molten Ge chalcogenides. We show that the anomalous volume contraction observed in the liquid 30 K above the eutectic temperature corresponds to a significant change of the Ge-Te partial structure factor. The detailed structural analysis shows that volume variations observed upon melting in Ge15Te85, as in liquid, GeSe and GeTe, can be explained in terms of the competition between two types of local environment of the germanium atoms. A symmetrical coordination octahedron is entropically favoured at high temperature, while an asymmetrical octahedron resulting from the local manifestation of the Peierls distortion is electronically favoured at lower temperatures. [less ▲]

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See detailProperties of ordinary and exotic hadrons
Stancu, Floarea ULg

in Few-Body Systems Supplementum (2001), 13

I discuss properties of ordinary and exotic hadrons as described by two distinct constituent quark models. These are the one gluon exchange (OGE) and the Goldstone boson exchange (GBE) models. I also ... [more ▼]

I discuss properties of ordinary and exotic hadrons as described by two distinct constituent quark models. These are the one gluon exchange (OGE) and the Goldstone boson exchange (GBE) models. I also discuss the interaction between hadrons starting from their quark structure. The case of the $NN$ is presented in some details. [less ▲]

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See detailProperties of spark plasma sintered nanostructured Zn1+xSb
Birkel, Christina S.; Claudio, Tania; Panthoefer, Martin et al

in Physica Status Solidi A. Applications and Materials Science (2011), 208(8), 1913-1919

Engineering materials with specific physical properties has recently focused on the effect of nanoscopic inhomogeneities at the 10 nm scale. Such features are expected to scatter medium and long ... [more ▼]

Engineering materials with specific physical properties has recently focused on the effect of nanoscopic inhomogeneities at the 10 nm scale. Such features are expected to scatter medium and long-wavelength phonons lowering thereby the thermal conductivity of the system without simultaneously decreasing the charge transport (phonon-glass electron-crystal concept). A new Zn1+xSb nanophase obtained by a wet chemical approach was densified by spark plasma sintering (SPS). Investigations on compounds subsumed as ``Zn4Sb3'' always suffer from its low thermal stability and the contamination of the nanoparticles with solvents and additives used in the synthesis. In order to gain insight into this compound's electronic properties we investigated a material free from remnants of the synthesis but contaminated with a small amount of well-characterized decomposition product, i.e., ZnSb. To investigate the influence of the sintering process on the densified samples, different SPS conditions were applied. Four different conditions were used with heating rates between 160 degrees and 230 degrees C/min, sintering temperatures between 130 and 190 degrees C and sintering times between 3 and 6 min. Powders from the surface of the pellets were subject to powder X-ray diffraction (XRD) yielding information about the surface composition. Small pieces of the pellets were also characterized using high-energy synchrotron radiation scattering in order to reveal the phase compositions inside the pellets. Small changes in the sintering conditions of the samples were found to have a large influence on the resulting sample compositions. In addition, the phase compositions on the surface differ significantly from the ones inside the pellets which show a much higher grade of decomposition. The density and morphology of the obtained pellets have been investigated by means of laser microscopy and scanning electron microscopy (SEM). The low density and porosity of the different pellets is a result of the graphite pressing tool which has to be used to ensure the temperature control during the SPS process. (C) 2011 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim [less ▲]

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See detailProperties of the DNA product of reverse transcription of turnip yellow mosaic virus RNA preparations.
Demeure, M.; Kummert, Jean; Portetelle, Daniel ULg et al

in Virology (1977), 81

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See detailProperties of the general N-Higgs-doublet model. I. The orbit space
Ivanov, Igor ULg; Nishi, Celso

in Physical Review. D : Particles and Fields (2010), 82(1), 0150141-16

We study the scalar sector of the general N-Higgs-doublet model via geometric constructions in the space of gauge orbits. We give a detailed description of the shape of the orbit space both for general N ... [more ▼]

We study the scalar sector of the general N-Higgs-doublet model via geometric constructions in the space of gauge orbits. We give a detailed description of the shape of the orbit space both for general N and, in more detail, for N=3. We also comment on remarkable analogies between the N-Higgs-doublet model and quantum information theory. [less ▲]

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See detailProperties of the general NHDM. II. Higgs potential and its symmetries
Ivanov, Igor ULg

in Journal of High Energy Physics [=JHEP] (2010), 2010(7), 1-31

We continue our analysis of the general N-Higgs-doublet model and focus of the Higgs potential description in the space of gauge orbits. We develop a geometric technique that allows us to study the global ... [more ▼]

We continue our analysis of the general N-Higgs-doublet model and focus of the Higgs potential description in the space of gauge orbits. We develop a geometric technique that allows us to study the global minimum of the potential without explicitly finding its position. We discuss symmetry patterns of the NHDM potential, and illustrate the general discussion with various specific variants of the three-Higgs-doublet model. [less ▲]

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See detailProperty tax and Land Use Management in Vietnam
Trinh, Hong Loan ULg

Conference given outside the academic context (2010)

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