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See detailInfluence of the balls kinematics and ball/race contact models on quasi-static approaches for ball bearing
Servais, Christophe ULg; Bozet, Jean-Luc ULg

Conference (2016, May 17)

The frictional power dissipated within dry lubricated ball bearings is a prime concern, especially for high speed applications. Nevertheless, the exact balls behavior is still a source of interrogations ... [more ▼]

The frictional power dissipated within dry lubricated ball bearings is a prime concern, especially for high speed applications. Nevertheless, the exact balls behavior is still a source of interrogations. Firstly, a comparison of several ball/race contact models has been performed by prescribing the kinematical variables. This has been done by using an existing quasi-static approach to reach the ball bearing equilibrium. Secondly, a parametric study has been carried out on the ball kinematics. This time the contact model remained fixed. The results demonstrate the predominance of the kinematics on the ball bearing behavior with an emphasis on the dissipated power within ball/race contacts. This shows that the kinematics must be rightly computed. On the other hand, the ball/race contact model doesn’t necessitate a high refinement in order to evaluate the ball bearing equilibrium. Conversely, this refinement is essential for a precise evaluation of the power losses. [less ▲]

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See detailInfluence of the balls kinematics of axially loaded ball bearings on Coulombic frictional dissipations
Bozet, Jean-Luc ULg; Servais, Christophe ULg

in Journal of Tribology (2017), 139(1),

Ball bearings have been used for a long time. Nevertheless, the description of their behavior remains incomplete in spite of the large number of surveys dedicated to ball bearings. Particularly, the exact ... [more ▼]

Ball bearings have been used for a long time. Nevertheless, the description of their behavior remains incomplete in spite of the large number of surveys dedicated to ball bearings. Particularly, the exact balls kinematics has still to be addressed in depth. This paper proposes a new way to calculate the balls kinematics by using a simplified quasi-static approach for dry lubricated and axially loaded ball bearings. This method does not use the classical restrictive race control assumptions. More specifically, the role played by the balls kinematics is emphasized by means of the power dissipated within contacts between balls and races. The need for a correct evaluation of the balls behavior is illustrated by using an example, viz. a ball bearing of cryogenic engine turbopump. Indeed, the dissipated power is one of the main concerns in this particular case. [less ▲]

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See detailInfluence of the BGE composition on analyte response in CD-mediated NACE-MS
Servais, Anne-Catherine ULg; Fillet, Marianne ULg; Mol, Roelof et al

in Electrophoresis (2010), 31(7), 1157-1161

The influence of the BGE composition, including the addition of a single-isomer sulfated beta-CD derivative, on the ionization performance of the model compound carvedilol in NACE-ESI-MS was studied using ... [more ▼]

The influence of the BGE composition, including the addition of a single-isomer sulfated beta-CD derivative, on the ionization performance of the model compound carvedilol in NACE-ESI-MS was studied using an alternative infusion method. This approach employs voltage-induced infusion of the BGE containing the analyte, and takes into account the effects of variations in EOF and effective analyte mobility on the ESI-MS intensity. First, the optimal composition of the sheath liquid for CE-MS in terms of signal abundance and stability was determined. The BGE ammonium formate, acetate, and camphorsulfonate were found to have similar effects on analyte ionization. Addition of single-isomer sulfated beta-CD derivatives (available as sodium salt) to the BGE revealed that the anionic CD derivatives did not give rise to the same ionization suppression effect. This result can be attributed to differences in the dissociation state of these sodium salts. Finally, it is shown that information about chiral selectivity can also be obtained with the applied infusion method. [less ▲]

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See detailInfluence of the capillary temperature and the source pressure on the internal energy distribution of electrosprayed ions
Gabelica, Valérie ULg; De Pauw, Edwin ULg; Karas, Michael

in International Journal of Mass Spectrometry (2004), 231(2-3), 189-195

The internal energy distributions in a heated capillary nano-electrospray source have been determined using the "survival yield" method. At low capillary temperatures, the internal energy distribution is ... [more ▼]

The internal energy distributions in a heated capillary nano-electrospray source have been determined using the "survival yield" method. At low capillary temperatures, the internal energy distribution is characterized by a low-energy tail, which can be attributed to a fraction of ions not fully desolvated in the heated capillary. This low-energy tais is shown to disappear when the source pressure is increased. This explains why increased source pressure is favorable in the case of highly hydrophilic compounds or non-covalent complexes in order to achieve sufficient desolvation without fragmentation. It is also shown that "high temperature-low voltage" are not equivalent to "low temperature-high voltage" source conditions. These observations are important for fundamental issues as well as for source-CID mass spectral library searching applications. [less ▲]

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See detailInfluence of the carbon texture of platinum/carbon aerogel electrocatalysts on their behaviour in a Proton Exchange Membrane Fuel Cell cathode
Ouattara-Brigaudet, M.; Berthon-Fabry, S.; Beauger, C. et al

in International Journal of Hydrogen Energy (2012), 37

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See detailInfluence of the cardiac cycle on time-intensity curves using multislice dynamic magnetic resonance perfusion
NCHIMI LONGANG, Alain ULg; MANCINI, Isabelle; BROUSSAUD, Thomas K. Y.

in International Journal of Cardiovascular Imaging (The) (2014), 30

Flow and pressure variations cause potential changes in magnetic resonance imaging (MRI) signal intensity across the cardiac cycle. Nevertheless, cardiac dynamic contrast-enhanced (perfusion) MRI is ... [more ▼]

Flow and pressure variations cause potential changes in magnetic resonance imaging (MRI) signal intensity across the cardiac cycle. Nevertheless, cardiac dynamic contrast-enhanced (perfusion) MRI is performed and analyzed regardless of the cardiac phase. We investigate whether the cardiac phase impacts myocardial and left ventricle (LV) cavity time intensity curves (TICs) at rest and during vasodilatation. Fifteen healthy volunteers (seven females, eight males; mean age: 32.5 ± 9.3 years; age range: 19–49 years) were included in this prospective study. They underwent four separate short-axis multislice (apical, mid and basal) LV perfusion MRI, with different electrocardiogram-triggering during normal vasotone and adenosine-stress. TIC parameters were extracted from the myocardium and the LV cavity. General linear mixed model analyses were used to evaluate their variability according to vasotone, cardiac phase and slice-position. Maximal enhancement and normalized Steepest slopes were higher at stress than at rest (p values <0.001). A similar trend towards higher inflow was shown on systole versus diastole in the LV cavity and diastole versus systole in the myocardium (p < 0.05).These TIC parameters were slice-position dependent, as the inflow decreased from the base to the apex in the LV, and peaked on the mid-slice for the myocardium. There are significant variability of both the LV and the myocardial TICs, with respect to the cardiac cycle phase and the slice position where imaging actually takes place. These appeal to measurement standardization for a better intra- and inter-study reproducibility. [less ▲]

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See detailInfluence of the chemical composition on the thixoformability of steels
Pierret, Jean-Christophe ULg; Rassili, Ahmed ULg; Vaneetveld, Grégory ULg et al

in International Journal of Material Forming (2009)

This work deals with the qualification of a variety of steels for their shaping by the thixoforging process. This technology requires setting up a globular microstructure inside the material during ... [more ▼]

This work deals with the qualification of a variety of steels for their shaping by the thixoforging process. This technology requires setting up a globular microstructure inside the material during reheating to a temperature between the solidus and liquidus. As the evolution of the liquid fraction is strongly connected to the steel composition, it is useful to understand how low carbon steel could be alloyed and still thixoformable. The most critical parameter for this is the carbon content. In this study, a theoretical analysis of the phase evolution during the reheating has been performed on the MT Data software to investigate the influence of alloying elements. These first results have been confirmed by Differential Thermal Analysis and by inductive heating experiments on steel slugs. Finally, some parts have been shaped using a thixoforming tool mounted on a hydraulic press. Micrographs of reheated slugs as well as of actual parts are also presented in this paper. [less ▲]

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See detailInfluence of the composition of the repairing mortars on adherence
Courard, Luc ULg; Wiertz, Jean; Darimont, Anne ULg et al

in Van Gemert, Dionys (Ed.) Proceedings of the VIIIth International Congress on Polymers in Concrete (1995)

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See detailInfluence of the contraction mode on the tendon structure - Rat model
Kaux, Jean-François ULg; Drion, Pierre ULg; Besançon, Benoît et al

in 2nd Congress of European College of Sport & Exercise Physicians - Conference Brochure 2010: Abstracts and CVs (2010, September 09)

Introduction: Tendinopathies are common in sport and affect both upper and lower limbs. Eccentric rehabilitation is a successful way of treating them and now is becoming the “gold treatment”. Although ... [more ▼]

Introduction: Tendinopathies are common in sport and affect both upper and lower limbs. Eccentric rehabilitation is a successful way of treating them and now is becoming the “gold treatment”. Although clinical results are very favorable, beneficial morphological and histological effects have not yet been elucidated. The aim of our experiment was to determine if there exist any intrinsic modifications in a tendon trained in concentric or eccentric modes, in a rat model. Methods: 18 rats were divided into 3 groups: 6 for the control group, without physical restraint; 12 for a training of1 hour, 3 times a week, for 5 weeks, at a speed of 17m/min (1km/h), on a inclined treadmill: 6 rats running uphill at +15° for the concentric effort (group C) and 6 rats running downhill at -15° for the eccentric effort (group E). After this training period, the Achilles, patellar and tricipital tendons of both limbs were surgically removed in all 18 rats. Tendons taken from five rats of each group were subjected to a tensile test up to rupture using a “cryo” jaw. Tendons of the remaining rat of each group were subjected to a histological study. Results: The results showed significant changes in group E only: (1) an increase of the force required to rupture the patellar and tricipital tendons; (2) an improvement of the ratio between the force necessary to rupture the tricipital tendon and the body mass of the rats; (3) an increase of the surface area of the section of the tricipital tendon. No significant change was observed as far as constraint was concerned between groups. Histologically, we saw, in the group E, more peripheral blood vessels and a greater proportion of collagen. Conclusion: This study showed that the mechanical properties of tendon tissue are enhanced by eccentric training. Tendons become stronger, the amount of collagen increases and there is probably more interaction between collagen fibers (mechanotransduction). [less ▲]

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See detailInfluence of the convective flux perturbation on stellar oscillations: application to Delta Scuti and Gamma Doradus stars
Grigahcene, A.; Dupret, Marc-Antoine ULg; Garrido, R. et al

in Communications in Asteroseismology (2004), 145

We present a theory of convection-oscillation interaction. In our nonradial nonadiabatic pulsation code, the variation of the convective flux (radial and transversal components) is taken into account ... [more ▼]

We present a theory of convection-oscillation interaction. In our nonradial nonadiabatic pulsation code, the variation of the convective flux (radial and transversal components) is taken into account, following the theory of M. Gabriel, within the mixing length approach. We explore the influence of the convective flux variation on mode stability near the red-edge of the Delta Scuti instability strip and the excitation mechanisms of Gamma Doradus stars. [less ▲]

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See detailInfluence of the core on the 3d orbital before and after the collapse
Hansen, J E; Meyer, M; Sonntag, B et al

in Atomic and Molecular Photoionization (1996)

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See detailInfluence of the Counterpoise Correction on the Optimized Relativi Degrees of Freedom in the H-Bonded Complex Water-Formamide
Dehareng, Dominique ULg; Dive, Georges ULg; Ghuysen, Jean-Marie ULg

in Theoretica Chimica Acta (1992), 81(4-5), 281-290

The correction of the basis set superposition error by the counterpoise method has been investigated at the SCF level for the weak H-bonded water-formamide complex and the results have been compared with ... [more ▼]

The correction of the basis set superposition error by the counterpoise method has been investigated at the SCF level for the weak H-bonded water-formamide complex and the results have been compared with the uncorrected results at the SCF, post SCF and semi-empirical AM1 and MNDO levels. Our particular concern has been the determination of the three optimized relative degrees of freedom and the relative stability of three C(s) geometrical conformations. The conclusions are that the counterpoise correction weakly conditions the variation in the degrees of freedom and the relative stabilities of the three conformers. The correction is obviously inadequate to describe intramolecular deformation. [less ▲]

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See detailInfluence of the crosslinker type on the chromatographic properties of hydrophilic sulfoalkylbetaine-type monolithic columns.
Liu, Chusheng; Chen, Weijia; Yuan, Guangxin et al

in Journal of chromatography. A (2014), 1373

In order to investigate the effects of the crosslinker on the separation performance of polar zwitterionic sulfoalkylbetaine-type monolithic columns, three crosslinkers, i.e. 1,4-bis(acryloyl)piperazine ... [more ▼]

In order to investigate the effects of the crosslinker on the separation performance of polar zwitterionic sulfoalkylbetaine-type monolithic columns, three crosslinkers, i.e. 1,4-bis(acryloyl)piperazine (PDA), ethylene dimethacrylate (EDMA) and N,N'-methylenebisacrylamide (MBA), were copolymerized with the hydrophilic monomer N,N-dimethyl-N-acryloyloxyethyl-N-(3-sulfopropyl)ammonium betaine (SPDA). The chromatographic properties of the three hydrophilic sulfoalkylbetaine-type monolithic columns, including column efficiency, permeability, porosity and separation mechanism, were systematically compared using scanning electron microscopy or micro-HPLC. Good selectivity in micro-HPLC separations was achieved on all three monolithic columns. The results indicate that the polarity of sulfoalkylbetaine-type monolithic columns may be related to the polarity of the crosslinker, which further affects column selectivity and efficiency. A particularly high column efficiency (100,000 plates/m) was obtained on the novel poly(SPDA-co-PDA) monolithic column at a linear velocity of 1mm/s using thiourea as test analyte. A higher resolution was also observed for nucleobases, nucleosides and hydrophilic organic acids on this novel poly(SPDA-co-PDA) monolithic column compared to the other two columns. [less ▲]

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See detailInfluence of the crustal magnetic field on the Mars aurora electron flux and UV brightness
Bisikalo, D. V.; Shematovich, V. I.; Gérard, Jean-Claude ULg et al

in Icarus (2017), 282

Observations with the SPICAM instrument on board Mars Express have shown the occasional presence of localized ultraviolet nightside emissions associated with enhanced energetic electron fluxes. These ... [more ▼]

Observations with the SPICAM instrument on board Mars Express have shown the occasional presence of localized ultraviolet nightside emissions associated with enhanced energetic electron fluxes. These features generally occur in regions with significant radial crustal magnetic field. We use a Monte-Carlo electron transport model to investigate the role of the magnetic field on the downward and upward electron fluxes, the brightness and the emitted power of auroral emissions. Simulations based on an ASPERA-3 measured auroral electron precipitation indicate that magnetic mirroring leads to an intensification of the energy flux carried by upward moving electrons- from about 20% in the absence of crustal magnetic field up to 33-78% when magnetic field is included depending on magnetic field topology. Conservation of the particle flux in a flux tube implies that the presence of the B-field does not appreciably modify the emission rate profiles for an initially isotropic pitch angle distribution. However, we find that crustal magnetic field results in increase of the upward electron flux, and, consequently, in reduction of the total auroral brightness for given energy flux of precipitating electrons. [less ▲]

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