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See detailExperimental irreversible passive energy transfer in coupled nonlinear oscillators
McFarland, D. Michael; Kerschen, Gaëtan ULg; Kowtko, Jeffrey J. et al

in Fifth EUROMECH Nonlinear Dynamics Conference, Eindhoven, 2005 (2005, August)

Experimental verification of passive nonlinear energy pumping in two configurations of coupled oscillators with essential nonlinearities is carried out. In the experiments presented the nonlinear ... [more ▼]

Experimental verification of passive nonlinear energy pumping in two configurations of coupled oscillators with essential nonlinearities is carried out. In the experiments presented the nonlinear attachment interacts with a single linear mode, and passive targeted energy transfer occurs at a single ‘fast’ frequency in the neighborhood of the eigen frequency of a linear mode. Good agreement between simulated and experimental results is observed, in spite of the strongly (essentially) nonlinear and transient nature of the dynamics of the systems considered. The experiments bear out earlier predictions that a significant fraction of the energy introduced directly to a linear structure by an external impulsive (broadband) load can be transferred (pumped) to an essentially nonlinear attachment, and dissipated there locally without spreading back to the system. In addition, the reported experimental results confirm that (a) nonlinear energy pumping in systems of coupled oscillators can occur only above a certain threshold of the input energy, and (b) there is an optimal value of the energy input at which a maximum portion of the energy is absorbed and dissipated at the NES. [less ▲]

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See detailExperimental lifetime determination in neutral praseodymium (Pr I) and neodymium (Nd I)
Biémont, Emile ULg; Quinet, Pascal ULg; Svanberg, S. et al

in Journal of Physics B-Atomic Molecular and Optical Physics (2004), 37(7), 1381-1389

Radiative lifetime measurements have been performed, with a time-resolved laser-induced fluorescence technique, for 18 even-parity levels of Pr I and 15 odd-parity levels of Nd I. The new results are ... [more ▼]

Radiative lifetime measurements have been performed, with a time-resolved laser-induced fluorescence technique, for 18 even-parity levels of Pr I and 15 odd-parity levels of Nd I. The new results are compared with the few experimental data available in the literature and good agreement is found. However, fragmentary knowledge of the spectra prevents reliable calculation of branching fractions and calls for additional laboratory efforts in order to provide the astrophysicists with reliable transition probabilities needed for investigating the magnetic fields in chemically peculiar stars. [less ▲]

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See detailExperimental M1 Transition Rates in Highly Charged Krypton Ions
Träbert, E.; Beiersdorfer, P.; Brown, G. V. et al

in Physical Review. A (2001), 64

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See detailExperimental method for the assessment of agricultural spray retention based on high-speed imaging of drop impact on a synthetic superhydrophobic surface
Massinon, Mathieu ULg; Lebeau, Frédéric ULg

in Biosystems Engineering (2012), 112(1), 56-64

Spray retention is a critical stage in pesticide application since non-retained drops can result in reduced efficacy, economic loss and environmental contamination. Current methods of retention assessment ... [more ▼]

Spray retention is a critical stage in pesticide application since non-retained drops can result in reduced efficacy, economic loss and environmental contamination. Current methods of retention assessment are based either on field experiments or laboratory studies. The former are usually performed on whole plants under realistic spray application conditions but offer no insight into the physics behind the process whilst the latter mainly focus on drop impact physics but are usually restricted to unrealistically low drop speeds. The aim of the paper is to devise an experimental method to investigate retention at drop scale level as a function of operational parameters but under controlled realistic conditions. A device based on highspeed video was developed to study retention on a synthetic superhydrophobic surface for a moving agricultural nozzle. The sizes and velocities of the drops generated were measured immediately before impact using image analysis. Impact class proportions were established and transition boundaries between impact outcomes were quantified using Weber number. Two contrasting experiments were performed to investigate the ability of method to detect small parametric changes. The insignificant changes in spray pattern that occur from pressure changes, did not significantly affect impact class boundaries, but changed the proportion of drops in each class because of size and velocity variations. The use of a surfactant reduced the volume median diameter of the spray, increased impact speed and changed the impact class boundaries. The method should allow a precise parametric investigation of spray retention in laboratory and close to field conditions. [less ▲]

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See detailExperimental methods for Lode angle characterization in ductile fracture
Guzmán Inostroza, Carlos Felipe ULg

Diverse speeche and writing (2013)

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See detailExperimental modal analysis of a beam travelled by a moving mass using Hilbert Vibration Decomposition
Bertha, Mathieu ULg; Golinval, Jean-Claude ULg

Scientific conference (2014, July)

In this paper the problem of modal identification of time-varying system is investigated. To do so, a technique based on the sifting process of the Hilbert Vibration Decomposition (HVD) method is ... [more ▼]

In this paper the problem of modal identification of time-varying system is investigated. To do so, a technique based on the sifting process of the Hilbert Vibration Decomposition (HVD) method is presented. The key idea is to estimate the instantaneous frequency of the dominant mode, to extract its corresponding component by demodulation of the recorded signals and then to iterate with the subsequent dominant mode. In the case of multiple recorded signals, a source separation method is used as a preprocessing step to facilitate the identification of the instantaneous frequency for the following demodulation step. To illustrate the method, an experimental set-up consisting in a beam travelled by a non negligible mass is considered. The whole structure is randomly excited during the travel of the mass and some responses on the beam are recorded. [less ▲]

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See detailExperimental modal analysis of nonlinear structures using broadband data
Noël, Jean-Philippe ULg; Renson, Ludovic ULg; Grappasonni, Chiara ULg et al

in Proceedings of the International Modal Analysis Conference (IMAC) XXXIII (2015, February)

The objective of the present paper is to develop a rigorous identification methodology of nonlinear normal modes (NNMs) of engineering structures. This is achieved by processing experimental measurements ... [more ▼]

The objective of the present paper is to develop a rigorous identification methodology of nonlinear normal modes (NNMs) of engineering structures. This is achieved by processing experimental measurements collected under broadband forcing. The use of such a type of forcing signal allows to excite multiple NNMs simultaneously and, in turn, to save testing time. A two-step methodology integrating nonlinear system identification and numerical continuation of periodic solutions is proposed for the extraction of the individual NNMs from broadband input and output data. It is demonstrated using a numerical cantilever beam possessing a cubic nonlinearity at its free end. The proposed methodology can be viewed as a nonlinear generalization of the phase separation techniques routinely utilized for experimental modal analysis of linear structures. The paper ends with a comparison between this new nonlinear phase separation technique and a previously-developed nonlinear phase resonance method. [less ▲]

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See detailExperimental modal analysis of nonlinear vibrating structures using nonlinear normal modes
Peeters, Maxime ULg; Kerschen, Gaëtan ULg; Golinval, Jean-Claude ULg

in IV European Conference on Computational Mechanics, Paris, 2010 (2010)

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See detailExperimental modal analysis using blind source separation techniques
Poncelet, Fabien ULg; Kerschen, Gaëtan ULg; Golinval, Jean-Claude ULg

in International Conference on Noise and Vibration Engineering, Leuven, 2006 (2006)

Recently, statistical and empirical signal processing techniques such as the proper orthogonal decomposition and the Hilbert-Huang transform have shown promise for structural system identification. In the ... [more ▼]

Recently, statistical and empirical signal processing techniques such as the proper orthogonal decomposition and the Hilbert-Huang transform have shown promise for structural system identification. In the present study, experimental modal analysis is carried out by employing blind source separation techniques and by interpreting the response of a mechanical system as a static mixture of sources. Specifically, it is shown under which circumstances the normal coordinates of the vibration modes may be interpreted as virtual sources. The advantages and limitations of the proposed method will be discussed, and the procedure will be demonstrated using numerical applications. [less ▲]

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See detailExperimental model for the study by chemiluminescence of the activation of isolated equine leucocytes.
Benbarek, H.; Deby, Ginette ULg; Deby, C. et al

in Research in Veterinary Science (1996), 61(1), 59-64

The activation of human polymorphonuclear leucocytes (the respiratory burst) can be studied by measuring their chemiluminescent response. This technique was adapted to equine leucocytes to investigate the ... [more ▼]

The activation of human polymorphonuclear leucocytes (the respiratory burst) can be studied by measuring their chemiluminescent response. This technique was adapted to equine leucocytes to investigate the effects of cell number, activator concentration, enhancers of chemiluminescence, pH, temperature and inhibitors. Leucocytes were isolated from citrated blood from healthy horses and chemiluminescence was measured with a Bio-Orbit luminometer sensitive to 900 nm light. The optimal cell density for the maximal chemiluminescent response ranged from 10(6) to 10(7) leucocytes 600 microliters-1. Chemiluminescence increased as a function of temperature, and the concentrations of luminol, lucigenin and phorbol myristate acetate (PMA), and was pH related (optimal pH value = 8.0 for lucigenin and 8.5 for luminol). The inhibition of chemiluminescence by 5 x 10(-5) M azide was 88 per cent for luminol and 37 per cent for lucigenin. Superoxide dismutase (100 IU) totally inhibited the chemiluminescence response. Approximately 30 per cent variability in chemiluminescence was observed under the same assay conditions, depending on the origin of the leucocytes. Based on these results, the conditions selected for the measurement of equine leucocyte chemiluminescence were: 10(6) to 10(7) leucocytes 600 microliters-1, 1 x 10(-6)M PMA, 1 mM luminol or 0.4 mM lucigenin, physiological pH (7.4) and physiological temperature (37.8 degrees C). These conditions were similar to those used for measuring the chemiluminescent response of human leucocytes. [less ▲]

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See detailExperimental model of equine alveolar macrophage stimulation with TLR ligands.
Waldschmidt, Ingrid; Pirottin, Dimitri ULg; Art, Tatiana ULg et al

in Veterinary Immunology and Immunopathology (2013), 155(1-2), 30-37

Pulmonary diseases are common in horses and have a major economic impact on the equine industry. Some of them could be associated with an inadequate immune response in the lung, but methods to evaluate ... [more ▼]

Pulmonary diseases are common in horses and have a major economic impact on the equine industry. Some of them could be associated with an inadequate immune response in the lung, but methods to evaluate this response in horses are lacking. The aim of this study was to develop and validate an experimental model that could be applied in several physiological and pathological conditions to assess the innate immune response of equine pulmonary cells. Equine alveolar macrophages (AMs) obtained from bronchoalveolar lavages were isolated from other cells by adhesion. TLR2, 3, and 4 expression in AMs was studied and their responses to commercial ligands (respectively FSL-1, Poly(I:C), and LPS) were evaluated after determination of the appropriate dose and time of incubation. TLR responses were assessed by measuring cytokine production using (1) gene expression of TNFalpha, IFNbeta, Il-1beta, and IFNalpha by qPCR (indirect method); and (2) cytokine production for TNFalpha and IFNbeta by ELISA (direct method). TLR 2, 3, and 4 were expressed by AMs. TLR 2 stimulation with 10ng/mL of FSL-1 during 3h significantly increased IL-1beta and TNFalpha gene expression. TLR 3 stimulation with 1000ng/mL of Poly(I:C) during 1h increased IFNbeta, IFNalpha, Il-1beta and TNFalpha expression. TLR 4 stimulation with 100ng/mL of LPS during 3h increased TNFalpha, IFNbeta, and Il-1beta expression. Results obtained by ELISA quantification of TNFalpha and IFNbeta produced by AMs following stimulation during 6h were similar: FSL-1 increased TNFalpha production but not IFNbeta, Poly(I:C) and LPS increased production of IFNbeta and TNFalpha. In conclusion, pulmonary innate immunity of horses can be assessed ex vivo by measuring cytokine production following stimulation of AMs with TLR agonists. This experimental model could be applied under several conditions especially to improve the understanding of equine respiratory disease pathogenesis, and to suggest novel therapeutic opportunities. [less ▲]

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See detailExperimental Models of Inflammatory Bowel Disease
Louis, Edouard ULg; Belaiche, Jacques ULg

in Acta Gastro-Enterologica Belgica (1994), 57(5-6, Sep-Dec), 306-9

Etiology of inflammatory bowel disease (IBD) is still unknown. A lot of experimental models of these diseases have been developed during the last years. They can be classified as spontaneous and induced ... [more ▼]

Etiology of inflammatory bowel disease (IBD) is still unknown. A lot of experimental models of these diseases have been developed during the last years. They can be classified as spontaneous and induced models. Spontaneous models are infectious, genetic or of unknown etiology. Induced models are infectious, immune-mediated, chemical or genetic. All these models share some characteristics with IBD. In general, they are characterized by a chronic inflammation of the gut, and often, this inflammation appears secondary to mucosal abnormalities leading to an abnormal immune and inflammatory response toward luminal material. The most interesting models are thus those that share not only clinical and pathological characteristics with IBD, but also early mucosal abnormalities. From that point of view, the nonsteroidal anti-inflammatory drug (NSAID) enteropathy is probably one of the most interesting model for Crohn's disease (CD). In effect, this model shares an early modification with CD, that is increased intestinal permeability. In animals NSAID enteropathy, the increased intestinal permeability appears early after NSAID administration and is followed by inflammatory lesions. These lesions seem to be secondary to the increased permeability and depend on intraluminal materials, such as alimentary antigens or bacterial fragments. A possible link between the increased permeability and the inflammatory lesions could be an abnormal immune and inflammatory response toward the intraluminal materials. If the increased intestinal permeability in CD was confirmed, the same mechanisms could be implicated in its pathophysiology. [less ▲]

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See detailExperimental models to study measles virus persistence in the nervous system
Rammohan, K. W.; Dubois-Dalcq, M.; Rentier, Bernard ULg et al

in Progress in Neuropathology (1983), 5

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See detailExperimental models/cell model: organotypic cultures
Jacobs, Nathalie ULg; Delvenne, Philippe ULg

Conference (2007)

Detailed reference viewed: 21 (0 ULg)
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See detailExperimental modulation of neurotransmitter phenotype in adult dorsal root ganglion neurons.
Schoenen, Jean ULg; Delrée, P.; Jammaer, R. et al

Conference (1990, June 30)

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See detailExperimental nonlinear identification of an aircraft with bolted connections
De Filippis, Giovanni; Noël, Jean-Philippe ULg; Kerschen, Gaëtan ULg et al

in Proceedings of the International Modal Analysis Conference (IMAC) XXXIII (2015, February)

Aircraft structures are known to be prone to nonlinear phenomena, especially as they constantly become lighter and hence more flexible. One specific challenge that is regularly encountered is the modeling ... [more ▼]

Aircraft structures are known to be prone to nonlinear phenomena, especially as they constantly become lighter and hence more flexible. One specific challenge that is regularly encountered is the modeling of the mounting interfaces between aircraft subcomponents. Indeed, for large amplitudes of vibration, such interfaces may loosen and, in turn, trigger complex mechanisms such as friction and clearances. In this context, the present work intends to investigate the nonlinear dynamics of the Morane–Saulnier Paris aircraft, accessible at ONERA. This aircraft possesses multiple bolted connections between two external fuel tanks and wing tips. The objective of the paper is specifically to carry out an adequate identification of the numerous nonlinearities affecting the dynamics of this full-scale structure. Nonlinearity detection and the subsequent subspace-based parameter estimation have been performed on experimental data, collected during an on-ground test campaign. Nonlinearity detection is first achieved by the comparison of frequency response functions estimated at low excitation level, with those obtained at high amplitude level, yielding insight towards accurately characterizing the behavior of the bolted connections. Then, a nonlinear subspace identification method is applied to measured data to estimate the linear and nonlinear parameters of the structure and novel strategies and tools that overcome specific arisen problems are developed. [less ▲]

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See detailExperimental observation of flow characteristics over a Piano Key Weir
Machiels, Olivier ULg; Erpicum, Sébastien ULg; Dewals, Benjamin ULg et al

in Journal of Hydraulic Research (2011), 49(3), 359-366

The Piano Key Weir is a type of labyrinth weir using overhangs to reduce the foot print of the foundation. These are directly placed on a dam crest. Together with its high discharge capacity for low heads ... [more ▼]

The Piano Key Weir is a type of labyrinth weir using overhangs to reduce the foot print of the foundation. These are directly placed on a dam crest. Together with its high discharge capacity for low heads, this geometry makes these weirs interesting for dam rehabilitation. However, the Piano Key Weir is a new weir type, firstly designed in 2001 and built from 2006 by Electricité de France. Even if experimental studies confirmed its appealing discharge capacities, the flow upstream, over and downstream of this complex structure is still not well known. This research presents experimental test results performed on a 1:10 scale model. The experiments aim at determining the flow features along the weir depending on the upstream head. The flow conditions are characterized in terms of specific discharge, velocity, pressure, water level and streamlines along the weir. [less ▲]

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See detailExperimental parametric study and design of Piano Key Weirs
Machiels, Olivier; Pirotton, Michel ULg; Archambeau, Pierre ULg et al

in Journal of Hydraulic Research (2014), 52(3), 326-335

Piano Key Weirs are an effective solution for dam rehabilitation as well as new dam projects with a high level of hydraulic constraints. In order to improve the efficiency of their design, an experimental ... [more ▼]

Piano Key Weirs are an effective solution for dam rehabilitation as well as new dam projects with a high level of hydraulic constraints. In order to improve the efficiency of their design, an experimental study of the influence of the main geometric parameters has been performed. Thirty one configurations were tested for a wide range of discharges. The results of the study show the influence of the weir height, the keys widths and the overhangs lengths on the discharge capacity and flow characteristics. Based on hydraulic considerations, optimum values of the main geometric ratios are provided. An analytical formulation is developed to predict the discharge capacity of the weir as a function of its geometry. It shows an accuracy of 10% compared to the experimental results of this study and from other sources. [less ▲]

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See detailExperimental performance characterization of a new single room ventilation device with heat recovery
Gendebien, Samuel ULg; Georges, Emeline ULg; Prieels, Luc et al

in Proceedings of the 34th AIVC conference (2013, September)

Nowadays, important efforts are made to reduce the residential building energy consumption. In this context, a growing interest for heat recovery ventilation has been observed during the last decades. The ... [more ▼]

Nowadays, important efforts are made to reduce the residential building energy consumption. In this context, a growing interest for heat recovery ventilation has been observed during the last decades. The present paper focuses on a new single room ventilation with heat recovery. Double flow ventilation is achieved through the integration of the unit into windows ledges. The developed device is particularly suitable compared to traditional centralized heat recovery ventilation units for retrofitted houses due to the absence of air extracting and air pulsing ducts through the house. The first part of the paper consists in describing the characteristics and properties of the developed device (volume, components, flow configuration, advantages and drawbacks). In the second part of the paper, an experimental approach is presented to characterize the unit. The criteria of performance are based on: - Thermal effectiveness of the unit (testing of a recovery heat exchanger), - Hydraulic aspects (flows delivered by the unit vs energy supplied to the unit), - Acoustic aspects. The overall performance of the unit can be established based on the experimental results described here above. Cartography of performance (ratio between the recovered heat and the supply electrical power) can be drawn, depending on the flow rates delivered by the unit and the indoor/outdoor temperature difference. The last part of the paper compares the new system with natural, simple exhaust ventilation and traditional centralized systems in terms of primary energy, consumer price and carbon dioxide emissions. Results show that the presented device seems more competitive than natural and simple exhaust ventilation for the Belgian climate. The single room ventilation investigated in this paper also shows better performance than most of the centralized ventilation systems tested on site. [less ▲]

Detailed reference viewed: 115 (33 ULg)