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See detailDetermination of the complete bifurcation behaviour of aeroelastic systems with freeplay
Dimitriadis, Grigorios ULg

Scientific conference (2010, November 09)

In recent years there have been several applications of the nonlinear numerical continuation approach to aeroelastic systems with freeplay. While some of these have been successful, the general ... [more ▼]

In recent years there have been several applications of the nonlinear numerical continuation approach to aeroelastic systems with freeplay. While some of these have been successful, the general application of the method to such systems remains problematic. Numerical continuation can fail in the presence of complex bifurcations, numerous nearby periodic solution branches and other factors. In this paper, a three-part procedure for applying numerical continuation to aeroelastic systems with freeplay is proposed, designed to ensure that the complete periodic behavior is identified, even for systems with complex bifurcation diagrams. First, the equivalent linearization approach is used to determine approximations to the periodic solution branches of the nonlinear system. Then, a shooting-based technique is applied separately to each linearized approximation in order to pinpoint the nearest exact periodic solution. This process results in a cloud of periodic solutions, representing all the branches and sub-branches. Finally, a branch-following shooting procedure is applied to this cloud of points in order to obtain a complete description of every branch of periodic solutions. The procedure is demonstrated on a simple 3-DOF mathematical aeroelastic system with freeplay; it is shown that an extremely complex bifurcation is fully captured. The system's bifurcation diagram features multiple branch crossings, folds and loops. Its complete calculation allows the justification of several interesting LCO phenomena, such as aperiodic LCOs. [less ▲]

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See detailDetermination of the composition of cryolitic melts involved in the Hall-Heroult process by Raman spectroscopy
Malherbe, Cédric ULg; Gilbert, Bernard ULg

Conference (2012, August)

Considering our experience in the study of such highly corrosive media by Raman spectroscopy and since the bath spectrum is function of the molar NaF/AlF3 ratio and the Al2O3 content, we have proposed in ... [more ▼]

Considering our experience in the study of such highly corrosive media by Raman spectroscopy and since the bath spectrum is function of the molar NaF/AlF3 ratio and the Al2O3 content, we have proposed in the past to apply that technique to the direct determination of the melt composition . Recent instrumental developments on CCD based spectrometers have made the proposed method more feasible. This presentation will first demonstrate that, employing an updated instrument provided with new optical filters and a more sensitive CCD detector, better quality spectra are obtained. Afterward, new results relevant to the development of our analytical method for the direct determination of the molar NaF/AlF3 ratio and the Al2O3 content in cryolitic melt will be discuss. Different aspects of the calculation procedure will be illustrated:  Estimation and subtraction method of the Rayleigh decay from melt spectra;  Development of an internal normalisation procedure based on equilibria in the melt and assisted by home-made software;  Establishment of calibration curves for the determination of the molar ratio NaF/AlF3 in the melt;  Establishment of calibration curves for the determination of oxide content in the melt;  Overall procedure for the composition determination. [less ▲]

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See detailDetermination of the constants of the diurnal nutation
Folie, François ULg

in Science (1895), 2(45), 613-617

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See detailDetermination of the coordination number of particulate nano-materials using nitrogen adsorption
Gommes, Cédric ULg; Ravikovitch, Peter; Neimak, Alex

Scientific conference (2008, April)

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See detailDetermination of the Cosmological Density of Compact Objects using Gravitational Lensing and the HST
Claeskens, Jean-François ULg; Surdej, Jean ULg

in Benvenuti, Piero; Macchetto, F. D.; Schreier, E. J. (Eds.) Science with the Hubble Space Telescope - II (1996)

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See detailDetermination of the Enantiomers of 3-Tert.-Butylamino-1,2-Propanediol by High-Performance Liquid Chromatography Coupled to Evaporative Light Scattering Detection
Toussaint, B.; Duchateau, A. L.; van der Wal, S. et al

in Journal of Chromatography. A (2000), 890(2), 239-49

A method for the separation and quantitation of the enantiomers of 3-tert.-butylamino-1,2-propanediol by high-performance liquid chromatography and evaporative light scattering detection has been ... [more ▼]

A method for the separation and quantitation of the enantiomers of 3-tert.-butylamino-1,2-propanediol by high-performance liquid chromatography and evaporative light scattering detection has been developed. Separation of the enantiomers was performed in normal-phase liquid chromatography on a Chiralpak AS chiral stationary phase. The influence of the gas nature, gas pressure and temperature of the drift tube of the evaporative light scattering detector on the detection sensitivity was investigated. The method was validated in terms of linearity, limit of quantitation, accuracy and precision. The enantiomeric excess of (S)-3-tert.-butylamino-1,2-propanediol, used for the industrial synthesis of (S)-timolol, was measured from 0 to 94%. [less ▲]

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See detailDetermination of the Enantiomers of 3-Tert.-Butylamino-1,2-Propanediol by High-Performance Liquid Chromatography Using Mass Spectrometric Detection
Toussaint, B.; Streel, B.; Ceccato, Attilio ULg et al

in Journal of Chromatography. A (2000), 896(1-2), 201-7

The chiral synthesis of beta-blockers such as (S)-timolol requires a sensitive analytical method for the enantioseparation of its intermediate, 3-tert.-butylamino-1,2-propanediol, in the ng/ml range. The ... [more ▼]

The chiral synthesis of beta-blockers such as (S)-timolol requires a sensitive analytical method for the enantioseparation of its intermediate, 3-tert.-butylamino-1,2-propanediol, in the ng/ml range. The method developed is based on on-line normal-phase LC-MS-MS using a chiral stationary phase and an atmospheric pressure chemical ionization (APCI) interface. The MS detection of 3-tert.-butylamino-1,2-propanediol was first optimized with a pneumatically-assisted electrospray interface (ionspray). The APCI interface was then selected for LC-MS-MS because of the incompatibility of electrospray with n-hexane. The method was validated for both enantiomers in the 25-500 ng/ml concentration range. [less ▲]

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See detailDetermination of the Expansion Rate and Incidence of Rupture of Abdominal Aortic Aneurysms
Limet, Raymond ULg; Sakalihasan, Natzi ULg; Albert, Adelin ULg

in Journal of Vascular Surgery : Official Publication, the Society for Vascular Surgery and International Society For Cardiovascular Surgery, North American Chapter (1991), 14(4), 540-8

Expansion rate and incidence of rupture of abdominal aortic aneurysms in relation to their size is a source of debate. We studied 114 patients (out of a cohort of 752 consecutive patients admitted with ... [more ▼]

Expansion rate and incidence of rupture of abdominal aortic aneurysms in relation to their size is a source of debate. We studied 114 patients (out of a cohort of 752 consecutive patients admitted with abdominal aortic aneurysms) who were denied any immediate operation because of patient's refusal, high surgical risk, or small transverse diameter as assessed by CT scanning and ultrasonography. All patients not operated on underwent from two to six repeated examinations during an average follow-up period of 26.8 months (range, 3 to 132). Forty-seven patients (41.2%) were subsequently operated on electively because of marked increase of transverse diameter of the aneurysm (n = 44) or for other reasons (n = 3), with a death rate of 0%. Eighteen other patients underwent emergency operation for leaking or ruptured aneurysms, and there were five deaths. The incidence of rupture was clearly related to the final diameter value, rising from 0% in aneurysms less than 40 mm to 22% in large size aneurysms (greater than or equal to 50 mm). Among the 49 patients not operated on, one died of rupture before operation and five of causes unrelated to the disease. Using individual serial measurements, we determined the linear expansion rate of the aneurysm, which proved to be related to initial diameter values: 5.3 mm/year for diameters less than 40 mm (n = 49), 6.9 mm/year in the 40 to 49 mm group (n = 41), and 7.4 mm/year for diameters of 50 mm or more (n = 24).(ABSTRACT TRUNCATED AT 250 WORDS) [less ▲]

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See detailDetermination of the free/included piroxicam ratio in cyclodextrin complexes: comparison between UV spectrophotometry and differential scanning calorimetry
Van Hees, Thierry ULg; Piel, Géraldine ULg; Henry de Hassonville, Sandrine et al

in European Journal of Pharmaceutical Sciences (2002), 15(4), 347-353

Few analytical techniques allow to evaluate the inclusion yield of cyclodextrin-drug complexes, because most manufacturing processes give amorphous products, In this study we have developed an alternative ... [more ▼]

Few analytical techniques allow to evaluate the inclusion yield of cyclodextrin-drug complexes, because most manufacturing processes give amorphous products, In this study we have developed an alternative method to differential scanning calorimetry, to accurately determine the free/complexed piroxicam ratio by UV spectroscopy. This method is based on the differential solubility of the piroxicam-beta-cyclodextrin 1:2.5 mol/mol complex in water-acetonitrile (1:1 v/v) (Solvent A) or in anhydrous acetonitrile (Solvent B). both containing 0.05 M HCl. In anhydrous acetonitrile, beta-cyclodextrin is insoluble and the included drug remains entrapped, allowing the free piroxicam determination, while with 50% of water, the complex is totally dissolved, allowing the determination of the total guest content. This method was validated for linearity, precision and accuracy. The presence of cyclodextrin does not influence the assays, but more than 0.5% of water in Solvent B significantly affects the determination of the free piroxicam content. In comparison with differential scanning calorimetry, both delectability and precision were improved. It is now possible to analyse complexes with an inclusion purity greater than 99%. (C) 2002 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailDetermination Of The Functionality Of Common Apoa5 Polymorphisms
Talmud, Pj.; Palmen, J.; Putt, W. et al

in Journal of Biological Chemistry (2005), 280(31), 28215-20

Common variants of APOA5 have consistently shown association with differences in plasma triglyceride (TG) levels. These single nucleotide polymorphisms (SNPs) fall into three common haplotypes: APOA5*1 ... [more ▼]

Common variants of APOA5 have consistently shown association with differences in plasma triglyceride (TG) levels. These single nucleotide polymorphisms (SNPs) fall into three common haplotypes: APOA5*1, with common alleles at all sites; APOA5*2, with rare alleles of -1131T--> C, -3A--> G, 751G--> T, and 1891T--> C; and APOA5*3, distinguished by the c56C--> G (S19W). Molecular modeling of the apoAV signal peptide (SP) showed an increased angle of insertion (65 degrees ) at the lipid/water interface of Trp-19 SP compared with Ser-19 SP (40 degrees ), predicting reduced translocation. This was confirmed by 50% reduction of Trp-19-encoded SP.secretory alkaline phosphatase (SEAP) fusion protein secreted into the medium from HepG2 cells compared with the Ser-19.SEAP fusion protein (p < 0.002). Considering APOA5*2 SNPs, there was no significant difference in the relative luciferase expression in Huh7 cells transiently transfected with a -1131T construct compared with the -1131C (fragments -1177 to -516 or -1177 to -3). Similarly, for the -3A--> G in the Kozak sequence, in vitro transcription/translation assays and primer extension inhibition assays showed no alternate AUG initiation codon usage, demonstrating that -3A--> G did not influence translation efficiency. Although 1891T--> C in the 3'-untranslated region disrupts a putative Oct-1 transcription factor binding site, when inserted 3' of the luciferase gene the T--> C change demonstrated no significant difference in luciferase expression. Thus, association of APOA5*2 SNPs with TG levels is not due to the individual effects of any of these SNPs, although cooperativity between the SNPs cannot be excluded. Alternatively, the effect on TG levels may reflect the strong linkage disequilibrium with the functional APOC3 SNPs. [less ▲]

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See detailDetermination of the high strain rate forming properties of steel sheet
Verleysen, Patricia; Peirs, Jan; Duchene, Laurent ULg

in Complas XI (2011)

The strain rate dependence of the plastic yield and failure properties displayed by most metals affects energies, forces and forming limits involved in high speed forming processes. In this contribution a ... [more ▼]

The strain rate dependence of the plastic yield and failure properties displayed by most metals affects energies, forces and forming limits involved in high speed forming processes. In this contribution a technique is presented to assess the influence of the strain rate on the forming properties of steel sheets. In a first step, static and high strain rate tensile experiments are carried out in order to characterize the materials strain rate dependent behaviour. In a second step, the phenomenological Johnson-Cook model and physically-based Voce model are used to describe the constitutive material behaviour. The test results are subsequently used to calculate the forming limit diagrams by a technique based on the Marciniak-Kuczynski model. With the developed technique, static and dynamic forming limit diagrams are obtained for a commercial DC04 steel and a laboratory made CMnAl TRIP steel. The results clearly indicate that increasing the strain rate during a forming process can have a positive or negative effect. [less ▲]

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See detailDetermination of the Influence of Alloying Elements on Solidification Parameters for the Study of the Thixoformability of a Chromium Steel
Fraipont, Céline; Lecomte-Beckers, Jacqueline ULg

in Proceedings of The 10th Esaform Conference on Material Forming (2007)

This paper deals with the examination of the influence of alloying elements on the thixoformability of a chromium steel. It focuses on the liquid fraction curves of different chromium steel with and ... [more ▼]

This paper deals with the examination of the influence of alloying elements on the thixoformability of a chromium steel. It focuses on the liquid fraction curves of different chromium steel with and without modification of composition. The liquid fraction versus temperature has been obtained experimentally by differential thermal analysis (DTA), limited to low heating rates. The correlation between liquid fraction and temperature has been studied. The effect of modifications of composition was observed. [less ▲]

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See detailDetermination of the magnetic penetration depth in a superconducting Pb film
Brisbois, Jérémy ULg

Conference (2014, May 01)

By means of scanning Hall probe microscopy technique we accurately map the magnetic field pattern produced by Meissner screening currents in a thin superconducting Pb stripe. The obtained field profile ... [more ▼]

By means of scanning Hall probe microscopy technique we accurately map the magnetic field pattern produced by Meissner screening currents in a thin superconducting Pb stripe. The obtained field profile allows us to quantitatively estimate the Pearl length Λ without the need of pre-calibrating the Hall sensor. This fact contrasts with the information acquired through the spatial field dependence of an individual flux quantum where the scanning height and the magnetic penetration depth combine in a single inseparable parameter. The derived London penetration depth λL coincides with the values previously reported for bulk Pb once the kinetic suppression of the order parameter is properly taken into account. [less ▲]

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See detailDetermination of the magnetic penetration depth in a superconducting Pb film
Brisbois, Jérémy ULg; Raes, Bart; Van de Vondel, Joris et al

in Journal of Applied Physics (2014), 115(10), 103906

By means of scanning Hall probe microscopy technique we accurately map the magnetic field pattern produced by Meissner screening currents in a thin superconducting Pb stripe. The obtained field profile ... [more ▼]

By means of scanning Hall probe microscopy technique we accurately map the magnetic field pattern produced by Meissner screening currents in a thin superconducting Pb stripe. The obtained field profile allows us to quantitatively estimate the Pearl length Λ without the need of pre-calibrating the Hall sensor. This fact contrasts with the information acquired through the spatial field dependence of an individual flux quantum where the scanning height and the magnetic penetration depth combine in a single inseparable parameter. The derived London penetration depth λL coincides with the values previously reported for bulk Pb once the kinetic suppression of the order parameter is properly taken into account. [less ▲]

Detailed reference viewed: 110 (36 ULg)