Browsing
     by title


0-9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

or enter first few letters:   
OK
Full Text
Peer Reviewed
See detailLimit analysis of the statistics of quasi-steady non-linear aerodynamic forces for small turbulence intensities
Denoël, Vincent ULg

in Probabilistic Engineering Mechanics (2009), 24(4), 552-564

This paper focuses on the estimation of statistical characteristics of a specific quasi-steady wind loading used in buffeting analyses. In this loading, the intrinsic non-linearity of aerodynamic ... [more ▼]

This paper focuses on the estimation of statistical characteristics of a specific quasi-steady wind loading used in buffeting analyses. In this loading, the intrinsic non-linearity of aerodynamic coefficients is considered and approached by a polynomial expression of any a priori chosen degree. As rigorous developments of the statistical moments would result in impractical formulations, we suggest to consider the smallness of the turbulence intensities to construct, by means of a limit analysis, approximate expressions of the raw moments of aerodynamic forces. From these expressions, approximate cumulants and associated dimensionless characteristics, such as skewness and excess coefficients, are derived. The accuracy of the proposed analytical relations is assessed by comparison with Monte Carlo simulations, and the relevance of the sophisticated non-linear loading under consideration is compared to more traditional models. [less ▲]

Detailed reference viewed: 117 (13 ULg)
Full Text
Peer Reviewed
See detailLimit and Shakedown Analysis of 3D Steel Frames
Hoang, Van Long ULg; Nguyen, Dang Hung

in Engineering Structures (2008), 30

Detailed reference viewed: 46 (13 ULg)
Full Text
Peer Reviewed
See detailLimit current density in 2D metallic granular packings
Dorbolo, Stéphane ULg; Ausloos, Marcel ULg; Vandewalle, Nicolas ULg

in European Physical Journal B -- Condensed Matter (2003), 34(2), 201-204

The electrical properties of a 2D packed metallic pentagons have been studied. The electrical characterization of such metallic pentagon heaps, like i - V measurements, has been achieved. Two distinct ... [more ▼]

The electrical properties of a 2D packed metallic pentagons have been studied. The electrical characterization of such metallic pentagon heaps, like i - V measurements, has been achieved. Two distinct regimes have been shown. They are separated by a transition line along which the system exhibits a memory effect behavior due to the irreversible improvement of electrical contacts between pentagons (hot spots). A limit current density has been found. [less ▲]

Detailed reference viewed: 42 (7 ULg)
Full Text
See detailLimit Cycle Oscillation Control
Dimitriadis, Grigorios ULg

Poster (2000, December)

Over the last fifteen years the Aerospace industry has started to show a continuously increasing interest in the investigation of the vibrations of aircraft subjected to nonlinear structural and ... [more ▼]

Over the last fifteen years the Aerospace industry has started to show a continuously increasing interest in the investigation of the vibrations of aircraft subjected to nonlinear structural and aerodynamic forces. Here, a control scheme designed to alleviate or even stop some types of nonlinear aircraft vibrations is presented. [less ▲]

Detailed reference viewed: 30 (1 ULg)
Full Text
Peer Reviewed
See detailLimit Cycle Oscillation Control and Suppression
Dimitriadis, Grigorios ULg; Cooper, Jonathan E

in Aeronautical Journal (1999), 103(1023), 257-263

The prediction and characterization of the Limit Cycle Oscillation (LCO) behaviour of nonlinear aeroelastic systems has become of great interest recently. However, much of this work has concentrated on ... [more ▼]

The prediction and characterization of the Limit Cycle Oscillation (LCO) behaviour of nonlinear aeroelastic systems has become of great interest recently. However, much of this work has concentrated on determining the existence of LCOs. This paper concentrates on LCO stability. By considering the energy present in di®erent limit cycles, and also using the Harmonic Balance Method, it is shown how the stability of limit cycles can be determined. The analysis is then extended to show that limit cycles can be controlled, or even suppressed, by the use of suitable excitation signals. A basic control scheme is developed to achieve this, and is demonstrated on a simple simulated nonlinear aeroelastic system. [less ▲]

Detailed reference viewed: 156 (6 ULg)
Full Text
See detailLimit Cycle Oscillations of a Delta Wing in a Low Speed Wind Tunnel
Korbahti, Banu; Kagambage, Emile ULg; Andrianne, Thomas ULg et al

in Proceedings of ISMA2010 (2010, September 22)

Limit cycle oscillations involving Delta wings are an important area of research in modern aeroelasticity. Such phenomena can be the result of structural or aerodynamic nonlinearity. In this paper, a ... [more ▼]

Limit cycle oscillations involving Delta wings are an important area of research in modern aeroelasticity. Such phenomena can be the result of structural or aerodynamic nonlinearity. In this paper, a flexible half-Delta wing is tested in a low speed wind tunnel in order to investigate its dynamic response. Specifically, an investigation to determine the effects of a steady angle of attack on nonlinear Limit Cycle Oscillations (LCO) of a delta wing-plate model in low subsonic flow has been undertaken. It was found that, at several combinations of airspeed and angle of attack, the wing undergoes limit cycle oscillations. Two types of such oscillations are observed. One of them is low amplitude, low complexity limit cycle oscillations that occur at lower airspeeds; the other is high amplitude, high complexity limit cycle oscillations that occur a higher airspeeds and can appear abruptly. Some of the LCOs are the result of a subcritical Hopf bifurcation occurring at low steady angles of attack. At higher angles, a nontypical bifurcation was observed, whereby LCOs appear, grow with airspeed but then diminish and finally disappear as the airspeed is increased further. [less ▲]

Detailed reference viewed: 85 (29 ULg)
Full Text
Peer Reviewed
See detailLimit Cycle Prediction For Subsonic Aeroelastic Systems Using Nonlinear System Identification
Dimitriadis, Grigorios ULg; Vio, Gareth Arthur; Cooper, Jonathan Edward

in Ferman, M. A.; Petersson, B. A. T.; Rizzi, S. A. (Eds.) et al Proceedings of the VIII International Conference on Recent Advances in Structural Dynamics (2003, July)

The prediction of aeroelastic instabilities caused by nonlinear unsteady aerodynamic forces acting on aircraft has recently become an important area of research. Emphasis is placed on the capability to ... [more ▼]

The prediction of aeroelastic instabilities caused by nonlinear unsteady aerodynamic forces acting on aircraft has recently become an important area of research. Emphasis is placed on the capability to predict the occurrence of Limit Cycle Oscillations (LCOs) at both the design and prototype testing stages. In this paper, the prediction of LCOs is attempted for a simulated aeroelastic system subjected to nonlinear subsonic unsteady aerodynamic forces, using system identification. Response data from the simulated system are curve-fitted by means of a series of polynomial basis functions. This approach yields very accurate identified models of the actual system at individual flight conditions. These identified models are extrapolated to a global aeroelastic identified model. Using this model, the flight conditions at which LCOs occur is accurately predicted but the amplitude of the oscillations is underestimated. [less ▲]

Detailed reference viewed: 14 (2 ULg)
Full Text
Peer Reviewed
See detailLimit cycling behavior of a hybrid system: Application to percussive drilling
Depouhon, Alexandre ULg; Detournay, Emmanuel; Denoël, Vincent ULg

in Proceedings of the 2nd International Colloquium on Non-Linear Dynamics and Control of Deep Drilling Systems, Eindhoven, May 2012 (2012, May)

Detailed reference viewed: 68 (18 ULg)
Full Text
See detailLimitation des reliquats azotes apres cereales d'hiver par un raisonnement approprie de la fumure azotee.
Bodson, Bernard ULg; Falisse, André ULg; Guiot, Joseph

in Calvet, R. (Ed.) Nitrates-agriculture-eau: Symposium international (1990, November 07)

L'azote minéral présent dans le sol et son utilisation par le froment d'hiver ont été régulièrement suivis dans trente-cinq essais installés au cours de six années. Il en ressort que la fumure azotée ... [more ▼]

L'azote minéral présent dans le sol et son utilisation par le froment d'hiver ont été régulièrement suivis dans trente-cinq essais installés au cours de six années. Il en ressort que la fumure azotée optimale (dose totale et fractionnement) est propre à être calculé en fonction des facteurs pédoclimatiques, du passé cultural de la parcelle et de l'état de la culture. La fumure ainsi déterminée permet d'atteindre un rendement proche de l'optimum économique tout en limitant au maximum les reliquats en azote minéral après culture. [less ▲]

Detailed reference viewed: 59 (29 ULg)
Full Text
Peer Reviewed
See detailLa limitation du cumul de mandats par les députés wallons
Grandjean, Geoffrey ULg

in Courrier Hebdomadaire du CRISP (2015), 2255-2256

En moyenne, les représentants politiques belges cumulent entre cinq et huit mandats (dont la moitié sont rémunérés). Cette pratique contribue au développement des sentiments de méfiance que nourrit une ... [more ▼]

En moyenne, les représentants politiques belges cumulent entre cinq et huit mandats (dont la moitié sont rémunérés). Cette pratique contribue au développement des sentiments de méfiance que nourrit une partie de la population à l’égard des élus et des institutions. Dans un souci de bonne gouvernance, de nombreux citoyens et acteurs politiques appellent dès lors à une limitation des possibilités légales de cumul de mandats. La traduction récente la plus emblématique de cette préoccupation éthique est le décret décumul adopté en Région wallonne en 2010. Désormais, un député wallon n’a plus le droit de cumuler son mandat avec une fonction de bourgmestre, d’échevin ou de président d’un conseil de l’action sociale. Un quart des membres de chaque groupe politique représenté au Parlement wallon est cependant autorisé à cumuler. Les députés qui bénéficient de cette exception sont désignés sur la base de leur taux de pénétration électorale. Ce mécanisme est le fruit d’un accord politique conclu entre les partenaires du gouvernement régional (PS, Écolo, CDH). Son adoption a fait l’objet de débats nombreux et souvent tendus entre les partis politiques, en ce compris au sein de la majorité. Ce Courrier hebdomadaire retrace l’ensemble du processus législatif à la base du décret décumul. Il replace l’initiative dans son contexte et analyse le jeu des différents acteurs, en réservant une attention particulière aux divers arguments politiques, techniques et surtout juridiques qui ont été mobilisés. G. Grandjean se penche également sur les effets que le décret a eus pour les députés élus lors du scrutin régional wallon du 25 mai 2014. Enfin, il s’interroge sur l’avenir du décret décumul, que certains voudraient réformer, voire supprimer. [less ▲]

Detailed reference viewed: 52 (12 ULg)
Full Text
See detailLimitation du patrimoine commun
Leleu, Yves-Henri ULg

in Bourgeois, Marc; Leleu, Yves-Henri; Verbeke, A. (Eds.) et al Manuel de planification patrimoniale. Le couple, vie commune (2009)

Detailed reference viewed: 34 (6 ULg)
See detailThe limitation of the plausible values
Monseur, Christian ULg; Adams, Ray

in Garner, M. L.; Engelhard, G.; Wilson, M. (Eds.) Advances in Rasch Measurement (2010)

Detailed reference viewed: 98 (13 ULg)
Full Text
Peer Reviewed
See detailLimitation of the Pupil Replication Technique in the Presence of Instrumental Defects
Riaud, Pierre ULg; Mawet, Dimitri; Absil, Olivier ULg

in Astrophysical Journal Letters (2005), 628

Pupil replication has been proposed by Greenaway et al. as a new optical technique to improve the suppression of starlight in high dynamic imaging. This Letter extends numerical simulations in the two ... [more ▼]

Pupil replication has been proposed by Greenaway et al. as a new optical technique to improve the suppression of starlight in high dynamic imaging. This Letter extends numerical simulations in the two-dimensional case with various realistic imperfections (surface error, chromatic smearing, and pupil shift). These results demonstrate some strong limitations compared to single-pupil apodization techniques for exoplanet detection. [less ▲]

Detailed reference viewed: 7 (0 ULg)
Full Text
Peer Reviewed
See detailLimitations in transplantation of astroglia-biomatrix bridges to stimulate corticospinal axon regrowth across large spinal lesion gaps
Deumens, Ronald; Koopmans, Guido C; Honig, Wiel MM et al

in Neuroscience Letters (2006), 400(3), 208-212

Regrowth of injured axons across rather small spinal cord lesion gaps and subsequent functional recovery has been obtained after many interventions. Long-distance regeneration of injured axons across ... [more ▼]

Regrowth of injured axons across rather small spinal cord lesion gaps and subsequent functional recovery has been obtained after many interventions. Long-distance regeneration of injured axons across clinically relevant large spinal lesion gaps is relatively unexplored. Here, we aimed at stimulating long-distance regrowth of the injured corticospinal (CS) tract. During development, an oriented framework of immature astrocytes is important for correct CS axon outgrowth. Furthermore, a continuous growth promoting substrate may be needed to maintain a CS axon regrowth response across relatively large spinal lesion gaps. Hence, we acutely transplanted poly(D,L)-lactide matrices, which after seeded with immature astrocytes render aligned astrocyte-biomatrix complexes (R. Deumens, et al. Alignment of glial cells stimulates directional neurite growth of CNS neurons in vitro. Neuroscience 125 (3) (2004) 591-604), into 2-mm long dorsal hemisection lesion gaps. In order to create a growth promoting continuum, astrocyte suspensions were also injected rostral and caudal to the lesion gap. During 2 months, locomotion was continuously monitored. Histological analysis showed that astrocytes injected into host spinal tissue survived, but did not migrate. None of the astrocytes on the biomatrices survived within the lesion gap. BDA-labeled CS axons did not penetrate the graft. However, directly rostral to the lesion gap, 120.9 +/- 38.5% of the BDA-labeled CS axons were present in contrast to 12.8 +/- 3.9% in untreated control animals. The observed anatomical changes were not accompanied by locomotor improvements as analyzed with the BBB and CatWalk. We conclude that although multifactorial strategies may be needed to stimulate long-distance CS axon regrowth, future studies should focus on enhancing the viability of cell/biomatrix complexes within large spinal lesion gaps. [less ▲]

Detailed reference viewed: 34 (7 ULg)
Peer Reviewed
See detailLimitations of the current practice in neonatal PN across Europe
SENTERRE, Thibault ULg

in 3rd International Congress of Union of European Neonatal and Perinatal Societies (2012, November)

Detailed reference viewed: 4 (2 ULg)
Full Text
Peer Reviewed
See detailLimitations of the use of GFP transgenic mice in bone marrow transplantation studies.
Van Overstraeten-Schlogel, Nancy; Delgaudine, Marie ULg; Beguin, Yves ULg et al

in Leukemia & Lymphoma (2006), 47(7), 1392-3

Detailed reference viewed: 54 (6 ULg)
See detailLa limite fragile entre sensibilisation et manipulation
Blogie, Elodie; Devresse, Jenifer ULg

Article for general public (2014)

Detailed reference viewed: 22 (1 ULg)