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See detailFréquence et importance du charriage dans les rivières du massif ardennais
Houbrechts, Geoffrey ULg; Hallot, Eric ULg; Gob, F. et al

in Géographie physique et Quaternaire (2006), 60(3), 247-258

Le transport de la charge de fond de plusieurs rivières du massif ardennais (Belgique) a été analysé grâce à différentes techniques de marquage de galets (peinture, charge métallique, émetteurs radio ... [more ▼]

Le transport de la charge de fond de plusieurs rivières du massif ardennais (Belgique) a été analysé grâce à différentes techniques de marquage de galets (peinture, charge métallique, émetteurs radio). Ces rivières possèdent un bassin versant dont la taille est comprise entre 0,3 et 2700 km². Les observations ont permis de mettre en évidence le débit à partir duquel débute le charriage. Pour des rivières importantes (bassin versant supérieur à 500 km²), cette mise en mouvement se produit pour des débits légèrement inférieurs au débit à plein bord (0,7 à 1 Qb), débits qui se présentent en moyenne 5 à 11 jours par an. Dans les rivières ardennaises de taille intermédiaire (bassin versant compris entre 100 et 500 km²), on constate que le charriage débute pour un débit proche de 0,5 fois le débit à plein bord, avec des récurrences de l’ordre de 0,3 an et une durée de charriage variant entre 8 et 12 jours par an. Dans les rivières de dimension modeste (bassin versant inférieur à 100 km²), il apparaît que la mise en mouvement de la charge de fond se produit pour des débits compris entre 0,5 et 0,8 Qb, mais la récurrence de ces débits est relativement faible et le charriage peut se produire jusqu’à 20 jours par an. Par ailleurs, le transport solide par charriage a été évalué à l'aide de pièges à sédiments dans les rivières de petite dimension (bassin versant inférieur à 10 km²) ; il est relativement peu important dans les bassins forestiers (de l'ordre de 0,5 t.km-².an-1), notamment en raison de la multiplication des embâcles végétaux qui accroissent la rugosité et provoquent une forte dissipation d'énergie. Dans les rivières plus importantes, le transport solide a été estimé entre 0,4 et 2,5 t.km-².an-1 grâce à l'analyse des quantités curées systématiquement aux mêmes sites et à la réalisation de levés topographiques de contrôle. Nous avons ensuite analysé l’évolution des quantités charriées en fonction de la puissance spécifique au plein bord développée par ces rivières. La relation établie sur la base de ces données a permis de mettre en évidence le déficit en sédiments de certaines rivières ainsi que plusieurs facteurs influençant le charriage. [less ▲]

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See detailFrequency and clinical significance of pericardial friction rubs in the acute phase of myocardial infarction.
Dubois, Catherine ULg; Smeets, J. P.; Demoulin, J. C. et al

in European heart journal (1985), 6(9), 766-8

An early pericardial friction rub was noted in 23.4% of a population of 1264 consecutive patients admitted with acute myocardial infarction. The incidence of the rub did not vary with age, sex or past ... [more ▼]

An early pericardial friction rub was noted in 23.4% of a population of 1264 consecutive patients admitted with acute myocardial infarction. The incidence of the rub did not vary with age, sex or past cardiac history. The pericardial rub, however, was more often a complication of Q- than non-Q-wave infarcts (25.5% vs 10.5%, P greater than 0.001) and of anterior than inferior infarcts (35.3% vs 20.8%, P greater than 0.001). In comparing the 297 patients with a pericardial rub to the 967 others, we noted that the former group had a higher CK peak (1706 +/- 1110 UI l-1 vs 1189 +/- 1038 UI l-1, P greater than 0.001) and a higher incidence of Killip class greater than 1 (47.5% vs 33.2%, P greater than 0.001), atrial flutter or fibrillation (22.2% vs 9.3%, P greater than 0.001), second or third degree atrioventricular blocks (16.8% vs 9.4%, P greater than 0.001) and complete bundle branch block (14.5% vs 7.1%, P greater than 0.001). In spite of this, the development of a pericardial rub did not increase the in-hospital mortality (10.8% in patients with pericardial rub; 11.3% in those without). [less ▲]

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See detailFrequency dependence of Penh-index in healthy kittens
Kirschvink, N.; Vincke, G.; Marville, M. et al

in 20th Veterinary Comparative Respiratory Society - Boston, Massachussetts - USA - Octobre 2002 (2002)

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See detailFrequency domain approaches for the identification of an experimental beam with a local nonlinearity
Kerschen, Gaëtan ULg; Golinval, Jean-Claude ULg

in 20th International Modal Analysis Conference, Los Angeles, 2002 (2002, February)

Two approaches for the identification of multi-degree-of-freedom non-linear systems in the frequency domain have recently been introduced, i.e., the conditioned reverse path (CRP) method and the non ... [more ▼]

Two approaches for the identification of multi-degree-of-freedom non-linear systems in the frequency domain have recently been introduced, i.e., the conditioned reverse path (CRP) method and the non-linear identification through feedback of the outputs (NIFO) method. The key idea of these methods is to eliminate the distortions caused by the presence of non-linearities in frequency response functions. In this paper, the theoretical background of the CRP and NIFO methods is briefly recalled. Then, the ability of these techniques to identify the behaviour of an experimental cantilever beam with a local geometrical non-linearity is tested. The results obtained with both methods are compared and discussed. [less ▲]

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See detailA Frequency Domain Correlation Technique for Model Correlation and Updating
Pascual, Rodrigo; Golinval, Jean-Claude ULg; Razeto, Mario

Conference given outside the academic context (1997)

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See detailFrequency Domain Integral Equations for Acoustic and Electromagnetic Scattering Problems
Geuzaine, Christophe ULg; Reitich, F.; Turc, C.

in Proceedings of the Workshop on High-order methods for computational wave propagation and scattering (2007, September)

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See detailA frequency domain versus a time domain identification technique for nonlinear parameters applied to wire rope isolators
Kerschen, Gaëtan ULg; Lenaerts, Vincent; Marchesiello, Stefano et al

in Journal of Dynamic Systems Measurement and Control-Transactions of the Asme (2001), 123(4), 645-650

The present paper aims to compare two techniques for identification of nonlinear dynamical systems. The Conditioned Reverse Path method, which is a frequency domain technique, is considered together with ... [more ▼]

The present paper aims to compare two techniques for identification of nonlinear dynamical systems. The Conditioned Reverse Path method, which is a frequency domain technique, is considered together with the Restoring Force Surface method, a time domain technique. Both methods are applied for experimental identification of wire rope isolators and the results are compared. Finally, drawbacks and advantages of each technique are underlined. [less ▲]

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See detailFrequency effects of morphological units in derived and pseudoderived words in French dyslexics
Quemart, Pauline ULg; Casalis, Séverine

Poster (2007, August)

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See detailFrequency halving due to vortex pairing for the jet-slot oscillator
Billon, Alexis ULg; Glesser, Martin; Valeau, Vincent et al

Conference (2006, July)

At the outlet of the HVCA systems, whistling can occur, due to self-sustained oscillations. In this study, the ventilation outlet is modelled by a free plane subsonic jet impinging on a slotted plate ... [more ▼]

At the outlet of the HVCA systems, whistling can occur, due to self-sustained oscillations. In this study, the ventilation outlet is modelled by a free plane subsonic jet impinging on a slotted plate, leading to self-sustained tones production; this configuration is known as the jet-slot oscillator. The tone's frequency can be predicted through the vortex dynamics within the flow. For jet velocities higher than 16m/s, the tones couple with the flow-supply-duct’s resonances. These resonances control the vortex dynamics and reinforce the sound production, of about 20dB. Moreover, when the distance from the jet exit to the plate is increased and reaches 4.5 times the jet height, the fundamental frequency of the tones is suddenly halved due to some vortex pairing occurring at the end of the potential core of the jet. In this paper, the vortex pairing is observed with three different experimental techniques. Firstly, comparison between the radiated and the in-duct acoustic fields is conducted. Then the energy transfer from the fundamental to the sub-harmonics of the shear layer's velocity fluctuations is observed with anemometric measurements. Finally high speed flow visualizations are performed and allow to link the vortex impingement on the plate to the sound production. [less ▲]

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See detailThe frequency of Ap-stars with long rotation periods
Hensberge, H.; Manfroid, Jean ULg; Renson, Pierre ULg et al

in Astronomy and Astrophysics (1984), 132

Light variability was observed over time intervals of months to years in the stars HD 55540, HD 71066, HD 94660, and HD 187474. The significance of these results is discussed in terms of the frequency of ... [more ▼]

Light variability was observed over time intervals of months to years in the stars HD 55540, HD 71066, HD 94660, and HD 187474. The significance of these results is discussed in terms of the frequency of chemically peculiar CP2 stars showing (light) variability with periods longer than one month. This frequency, relative to the whole CP2 population, must lie somewhere between 4 and 16 percent. Observations, properly distributed in time, of a small subgroup of CP2 stars will be sufficient to obtain an accurate ratio of the number of LP-CP2 stars to the total number of CP2 stars. These observations, when continued until the periodicity is detected, could contribute also to the discussion whether these long periods should be identified with the rotation period. [less ▲]

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See detailThe frequency of cutaneous vasculitis is not increased in patients with rheumatoid arthritis treated with methotrexate
Kaye, O.; Beckers, C. C.; Paquet, P. et al

in Journal of Rheumatology (1996), 23(2), 253-257

OBJECTIVE: To analyse the frequency, type, and immunohistological features of clinical cutaneous vasculitis developing in patients with rheumatoid arthritis (RA) treated or not with methotrexate as well ... [more ▼]

OBJECTIVE: To analyse the frequency, type, and immunohistological features of clinical cutaneous vasculitis developing in patients with rheumatoid arthritis (RA) treated or not with methotrexate as well as their demographic, clinical and biological characteristics. METHODS: Ninety-one patients with RA receiving 9.5 mg/wk of methotrexate (MTX) were compared for an average observation time of 18 months to 130 matched patients with RA treated with various drugs excluding MTX. RESULTS: Whether receiving MTX or not, 5.4% of patients with RA developed a clinical cutaneous vasculitis. There were significant differences between both groups for 2 variables only: a higher percentage of polyneuropathies and a higher level of immune complex-plasma levels in non-MTX patients. The immunohistological analysis did not differentiate both groups. CONCLUSION: The percentage of cutaneous vasculitis that developed under MTX therapy was not different from that occurring as a natural complication of longstanding severe RA. [less ▲]

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See detailThe Frequency of Plasmodesmata Increases Early in the Whole Shoot Apical Meristem of Sinapis Alba L. During Floral Transition
Ormenese, Sandra ULg; Havelange, Andrée ULg; Deltour, Roger ULg et al

in Planta (2000), 211(3), 370-5

The frequency of plasmodesmata increases in the shoot apical meristem of plants of Sinapis alba L. induced to flower by exposure to a single long day. This increase is observed within all cell layers (L1 ... [more ▼]

The frequency of plasmodesmata increases in the shoot apical meristem of plants of Sinapis alba L. induced to flower by exposure to a single long day. This increase is observed within all cell layers (L1, L2, L3) as well as at the interfaces between these layers, and it occurs in both the central and peripheral zones of the shoot apical meristem. The extra plasmodesmata are formed only transiently, from 28 to 48 h after the start of the long day, and acropetally since they are detectable in L3 4 h before they are seen in L1 and L2. These observations indicate that (i) in the Sinapis shoot apical meristem at floral transition, there is an unfolding of a single field with increased plasmodesmatal connectivity, and (ii) this event is an early effect of the arrival at this meristem of the floral stimulus of leaf origin. Since (i) the wave of increased frequency of plasmodesmata is 12 h later than the wave of increased mitotic frequency (A. Jacqmard et al. 1998, Plant cell proliferation and its regulation in growth and development, pp. 67 78; Wiley), and (ii) the increase in frequency of plasmodesmata is observed in all cell walls, including in walls not deriving from recent divisions (periclinal walls separating the cell layers), it is concluded that the extra plasmodesmata seen at floral transition do not arise in the forming cell plate during mitosis and are thus of secondary origin. [less ▲]

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See detailFrequency of Solar-like Systems and of Ice and Gas Giants Beyond the Snow Line from High-magnification Microlensing Events in 2005-2008
Gould, A.; Dong, Subo; Gaudi, B. S. et al

in Astrophysical Journal (2010), 720

We present the first measurement of the planet frequency beyond the "snow line," for the planet-to-star mass-ratio interval –4.5 < log q < –2, corresponding to the range of ice giants to gas giants. We ... [more ▼]

We present the first measurement of the planet frequency beyond the "snow line," for the planet-to-star mass-ratio interval –4.5 < log q < –2, corresponding to the range of ice giants to gas giants. We find \endgraf\vbox{\begin{center}$\displaystyle{d^2 N{_{\rm pl}}\over d\log q\, d\log s} = (0.36\pm 0.15)\;{\rm dex}^{-2}$\end{center}}\noindentat the mean mass ratio q = 5 × 10 –4 with no discernible deviation from a flat (Öpik's law) distribution in log-projected separation s. The determination is based on a sample of six planets detected from intensive follow-up observations of high-magnification ( A>200) microlensing events during 2005-2008. The sampled host stars have a typical mass M host ~ 0.5 M sun [less ▲]

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See detailFrequency of Solar-Like Systems and Planet Mass-Ratio Distribution Function Beyond the Snow Line from High-Magnification Microlensing Events
Gould, A.; Dong, S.; Gaudi, B~S et al

in Astrophysical Journal (2010), 720

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See detailThe frequency ratio method and the new multiperiodic gamma Doradus star HD 218427
Rodríguez, E.; Amado, P. J.; Suárez, J. C. et al

in Astronomy and Astrophysics (2006), 450

Oscillations of gamma Dor-type were discovered in the star HD 218427 through simultaneous uvby photometric observations carried out in the year 2003. A few Hbeta-Crawford measurements were also collected ... [more ▼]

Oscillations of gamma Dor-type were discovered in the star HD 218427 through simultaneous uvby photometric observations carried out in the year 2003. A few Hbeta-Crawford measurements were also collected for calibration purposes and they locate this star well inside the gamma Dor instability region. We find HD 218427 to be deficient in metals, similar to other well-defined gamma Dor stars, and discuss the possibility that it has a lambda Boo nature. We carried out frequency analysis for different filters, including the combined "vby" filter, and five frequencies were found as significant with periods ranging between 0.3 and 0.8 days. The recently-developed frequency ratio method is used in order to identify the excited modes. The results are consistent with an l=2 identification for all the modes and with high radial quantum numbers (nË 40) for the three main observed periodicities. The possibility of multiplet structures is also discussed. However, no consistency is found when using the time-dependent convection treatment to discriminate modes. This disagreement can be due to the large rotation velocity taking place in HD 218427 and, consequently, the significant coupling between the modes. [less ▲]

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See detailFrequency, characteristics, and functions of future-oriented thoughts in daily life
D'Argembeau, Arnaud ULg; Renaud, Olivier; Van der Linden, Martial ULg

in Applied Cognitive Psychology (2011), 25

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See detailA Frequency-domain Approach to Subspace Identification of Nonlinear Systems, Application to Aerospace Structures
Noël, Jean-Philippe ULg

Doctoral thesis (2014)

The construction of mathematical models from experimental data is an essential step in the design process of engineering systems. The different tasks involved in this activity, from the measurement and ... [more ▼]

The construction of mathematical models from experimental data is an essential step in the design process of engineering systems. The different tasks involved in this activity, from the measurement and processing of data to the validation of the model, fall into the general field of system identification. In structural dynamics, the theoretical and experimental aspects of linear system identification have been successfully addressed since the early seventies, and mature analytical, computational and testing tools have emerged. Nonlinear system identification of vibrating structures has also enjoyed significant advances during the past few years. However, the common practice in industry is to ignore nonlinearities, arguably because their analysis is still regarded as impractical. The objective of this doctoral thesis is precisely to progress towards the development of a practical system identification methodology dedicated to real-life nonlinear structures. The first facet of the thesis is to introduce a nonlinear generalisation in the frequency domain of the so-called subspace identification methods. The proposed frequency-domain nonlinear subspace identification (FNSI) approach yields accurate models of large-scale systems comprising strong nonlinearities, closely-spaced modes and high damping. Because it can also estimate a large number of parameters while maintaining an acceptable computational burden, the second facet of this research is to investigate the utilisation of cubic splines as a very flexible means to model complex nonlinearities. Finally, the third facet of the present work is to derive nonlinear models with optimal statistical properties in the presence of measurement noise. This is achieved by embedding the FNSI method into the maximum likelihood identification framework. The scope of the identification and modelling tools developed in this thesis encompasses nonlinear structural systems originating from the various areas of vibration engineering, including the aerospace, mechanical or civil fields, amongst others. Throughout the dissertation, these tools are illustrated using numerical and experimental structures of increasing complexity, mainly related to aerospace applications. [less ▲]

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See detailA Frequency-Domain Processor for Maximum Resolution and Quicklook Processing of Wide-Swath ASAR Images
Barbier, Christian ULg; Piette, François; Renson, Luc et al

in Proc. EUSAR'96 Conference (1996)

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See detailA Frequency-Domain Processor for ScanSAR Images
Barbier, Christian ULg; Rosello-Guasch, Josep

in Preparing for the Future (1995), 5(4), 6-7

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