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 detailElastase-induced pulmonary emphysema in rats: comparison of computed density and microscopic morphometry.
Onclinx, Cecile; De Maertelaer, Viviane; Gustin, Pascal ULg et al

in Radiology (2006), 241(3), 763-70

PURPOSE: To prospectively compare computed tomographic (CT) quantification of pulmonary emphysema in elastase-treated rats with morphometry and to evaluate the information yielded by CT quantification and ... [more ▼]

PURPOSE: To prospectively compare computed tomographic (CT) quantification of pulmonary emphysema in elastase-treated rats with morphometry and to evaluate the information yielded by CT quantification and pulmonary function tests. MATERIALS AND METHODS: This study was approved by the local committee on care and use of animals in research. Thirty-six animals were used. Emphysema was produced by means of one or two tracheal injections of 300 IU of elastase, 8 weeks apart, in seven and 12 rats, respectively. As a control group, 10 rats received an injection of normal saline. The dynamic resistance, dynamic compliance, and static compliance were measured. CT was performed with 1-mm section thickness and 3-mm intervals. Relative areas of lung with attenuation coefficients lower than nine chosen thresholds (from -900 to -980 HU) and eight percentiles (from 1st to 18th percentiles) of the distribution of attenuation coefficients were compared with measurements of alveoli size--that is, mean interwall distance (MIWD) and mean perimeter per field (MP). Correlations between data obtained with thresholds and percentiles and MIWD and MP were investigated by means of Spearman coefficients (r(s)). Values of pulmonary function tests, most appropriate relative area threshold, and percentile were investigated by means of stepwise multiple regressions. RESULTS: For thresholds, relative surface area with attenuation coefficients less than -940 HU (RA(940)) showed the strongest correlations with findings at microscopy (r(s) = 0.676, P < .001 for MIWD; r(s) = -0.720, P < .001 for MP). For percentiles, the 3rd percentile showed the strongest correlations (r(s) = -0.647, P < .001 for MIWD; r(s) = 0.701, P < .001 for MP). Dynamic compliance and RA(940) or 3rd percentile were complementary for predicting microscopic measurements. CONCLUSION: In rats, RA(940) and the 3rd percentile reflect the extent of elastase-induced pulmonary emphysema and are complementary to dynamic compliance to predict microscopic extent. [less ▲]

Detailed reference viewed: 35 (2 ULg)
Full Text
Peer Reviewed
See detailElastic and inelastic transmission in guided atom lasers: A truncated Wigner approach
Dujardin, Julien ULg; Argüelles, Arturo; Schlagheck, Peter ULg

in Physical Review A (2015), 91

We study the transport properties of a Bose-Einstein condensate formed by an ultracold gas of bosonic atoms that is coupled from a magnetic trap into a one-dimensional waveguide. Our theoretical approach ... [more ▼]

We study the transport properties of a Bose-Einstein condensate formed by an ultracold gas of bosonic atoms that is coupled from a magnetic trap into a one-dimensional waveguide. Our theoretical approach to tackling this problem is based on the truncated Wigner method for which we assume the system to consist of two semi-infinite noninteracting leads and a finite interacting scattering region with two constrictions modeling an atomic quantum dot. The transmission is computed in the steady-state regime and we find a good agreement between truncated Wigner and matrix-product state calculations. We also identify clear signatures of inelastic resonant scattering by analyzing the distribution of energy in the transmitted atomic-matter wave beam. [less ▲]

Detailed reference viewed: 65 (4 ULg)
Full Text
Peer Reviewed
See detailElastic behaviour of bolted connection between cylindrical steel structure and concrete foundation
Hoang, Van Long ULg; Jaspart, Jean-Pierre ULg; Tran Xuan-Hoang et al

in Journal of Constructional Steel Research (2015), 115

Detailed reference viewed: 65 (12 ULg)
Peer Reviewed
See detailElastic behaviour of dock beetle adhesive structures
Gernay, Sophie-Marie ULg; Federle, Walter; Lambert, Pierre et al

Conference (2014, January)

The adhesion of many insects is mediated by liquid capillary bridges formed at the tips of multiple hair like structures (called setae) under their feet. Resulting adhesion forces can exceed a hundred ... [more ▼]

The adhesion of many insects is mediated by liquid capillary bridges formed at the tips of multiple hair like structures (called setae) under their feet. Resulting adhesion forces can exceed a hundred times the insect’s body weight and they are effective on a large variety of substrates, controllable in very short times and self cleaning. The underlying mechanism leading to these properties involves a complex coupling between the high aspect-ratio structures and the dynamic evolution of the liquid meniscus. In this experimental work, we concentrate on the role played by the compliance of seta tips. We analyse in detail their surface contact and deflection for perpendicular loading using interference microscopy. Challenges related to the micrometric scale of the phenomenon and the tiny amount of liquid are addressed. The results are rationalized through the lens of elasto-capillarity theory. [less ▲]

Detailed reference viewed: 14 (1 ULg)
Full Text
Peer Reviewed
See detailElastic damage to crack transition in a coupled non-local implicit discontinuous Galerkin/extrinsic cohesive law framework
Wu, Ling ULg; Becker, Gauthier ULg; Noels, Ludovic ULg

in Computer Methods in Applied Mechanics & Engineering (2014), 279

One current challenge related to computational fracture mechanics is the modeling of ductile fracture and in particular the damage to crack transition. On the one hand, continuum damage models, especially ... [more ▼]

One current challenge related to computational fracture mechanics is the modeling of ductile fracture and in particular the damage to crack transition. On the one hand, continuum damage models, especially in their non-local formulation which avoids the loss of solution uniqueness, can capture the material degradation process up to the localization of the damage, but are unable to represent a discontinuity in the structure. On the other hand cohesive zone methods can represent the process zone at the crack tip governing the crack propagation, but cannot account for the diffuse material damaging process. In this paper we propose to combine, in a small deformations setting, a non-local elastic damage model with a cohesive zone model. This combination is formulated within a discontinuous Galerkin nite element discretization. Indeed this DG weak formulation can easily be developed in a non-local implicit form and naturally embeds interface elements that can be used to integrate the traction separation law of the cohesive zone model. The method remains thus consistent and computationally e cient as compared to other cohesive element approaches. The effects of the damage to crack transition and of the mesh discretization are respectively studied on the compact tension specimen and on the double-notched specimen, demonstrating the efficiency and accuracy of the method. [less ▲]

Detailed reference viewed: 156 (33 ULg)
Full Text
See detailElastic meson nucleon and nucleon nucleon scattering: Models vs. all available data
Martynov, E.; Cudell, Jean-René ULg; Lengyel, A.

in Nicolescu, B. (Ed.) 11th International Conference On Elastic And Diffractive Scattering: Towards High Energy Frontiers: The 20th Anniversary Of The Blois Workshops (2005)

Detailed reference viewed: 13 (0 ULg)
Full Text
Peer Reviewed
See detailElastic properties of the oesophageal wall in the dynamic measurement of intrathoracic pressure in cattle
Lekeux, Pierre ULg; Hajer, R.; Breukink, H. J.

in Research in Veterinary Science (1984), 37(3), 366-367

The elastance of the midthoracic portion of the oesophagus was measured in 14 healthy Dutch Friesians. These were divided into three groups with mean ages of six, 126 and 1636 days, respectively. Mean ... [more ▼]

The elastance of the midthoracic portion of the oesophagus was measured in 14 healthy Dutch Friesians. These were divided into three groups with mean ages of six, 126 and 1636 days, respectively. Mean elastance was 0.17, 0.10 and 0.06 kPa ml-1, respectively. The calculated percentage of error, in relating the endoesophageal pressure with that in the thorax, was found to be smaller than 1 per cent for each animal. [less ▲]

Detailed reference viewed: 7 (1 ULg)
Full Text
Peer Reviewed
See detailElastic scattering of vortex electrons provides direct access to the Coulomb phase
Ivanov, Igor ULg; Seipt, Daniel; Surzhykov, Andrey et al

in Physical Review. D : Particles and Fields (2016), 94(7), 076001

Vortex electron beams are freely propagating electron waves carrying adjustable orbital angular momentum with respect to the propagation direction. Such beams were experimentally realized just a few years ... [more ▼]

Vortex electron beams are freely propagating electron waves carrying adjustable orbital angular momentum with respect to the propagation direction. Such beams were experimentally realized just a few years ago and are now used to probe various electromagnetic processes. So far, these experiments used the single vortex electron beams, either propagating in external fields or impacting a target. Here, we investigate the elastic scattering of two such aligned vortex electron beams and demonstrate that this process allows one to experimentally measure features which are impossible to detect in the usual plane-wave scattering. The scattering amplitude of this process is well approximated by two plane-wave scattering amplitudes with different momentum transfers, which interfere and give direct experimental access to the Coulomb phase. This phase (shift) affects the scattering of all charged particles and has thus received significant theoretical attention but was never probed experimentally. We show that a properly defined azimuthal asymmetry, which has no counterpart in plane-wave scattering, allows one to directly measure the Coulomb phase as function of the scattering angle. [less ▲]

Detailed reference viewed: 16 (3 ULg)
Full Text
Peer Reviewed
See detailElastic vector-meson production at HERA
Cudell, Jean-René ULg; Royen, I.

in Physics Letters B (1997), 397

Detailed reference viewed: 26 (1 ULg)
Full Text
Peer Reviewed
See detailElastic-plastic Behavior of semi-compact steel cross-sections
boissonade, Nicolas; Jaspart, Jean-Pierre ULg; Kettler, M et al

Conference (2011, May 10)

This paper details new design rules for semi-compact sections that are capable of capturing their characteristic elastic-plastic behavior. The formulae have been validated against experimental test ... [more ▼]

This paper details new design rules for semi-compact sections that are capable of capturing their characteristic elastic-plastic behavior. The formulae have been validated against experimental test results and hundreds of FEM-shell numerical results, on both H<shaped and hollow sections. They offer full continuities between cross-section classes and with all other design formulae of the code, for both sections and members. [less ▲]

Detailed reference viewed: 27 (1 ULg)
Peer Reviewed
See detailAn Elastic-visco-plastic Damage Model: from Theory to Application
Wang, X. C.; Habraken, Anne ULg

in Journal de Physique IV (1996, October), 6

Detailed reference viewed: 28 (3 ULg)
Full Text
See detailElasticité
Debongnie, Jean-François ULg

Book published by DEBONGNIE (Jean-François) (2011)

Mathematical preliminaries. Kinematics of a deformable body. Virtual work principle. Hyperelastic bodies. Linear elasticity. Torsion of prismatic beams. Boussinesq's problem. Hertz problem. Variational ... [more ▼]

Mathematical preliminaries. Kinematics of a deformable body. Virtual work principle. Hyperelastic bodies. Linear elasticity. Torsion of prismatic beams. Boussinesq's problem. Hertz problem. Variational principles. Plane elasticity. Technical beam theory. Theory of plates. External energetical theorems. Influence diagrams. Stability of elastic systems. Elasticity equations in curvilinear coordinates. [less ▲]

Detailed reference viewed: 333 (31 ULg)
Full Text
Peer Reviewed
See detailElastin density: Link between histological and biomechanical properties of vaginal tissue in women with pelvic organ prolapse?
DE LANDSHEERE, Laurent ULg; Brieu, Mathias; Blacher, Silvia ULg et al

in International Urogynecology Journal & Pelvic Floor Dysfunction (2016)

INTRODUCTION AND HYPOTHESIS: The aim of the study was to correlate histological and biomechanical characteristics of the vaginal wall in women with pelvic organ prolapse (POP). METHODS: Tissue samples ... [more ▼]

INTRODUCTION AND HYPOTHESIS: The aim of the study was to correlate histological and biomechanical characteristics of the vaginal wall in women with pelvic organ prolapse (POP). METHODS: Tissue samples were collected from the anterior [point Ba; POP Questionnaire (POP-Q)] and/or posterior (point Bp; POP-Q) vaginal wall of 15 women who underwent vaginal surgery for POP. Both histological and biomechanical assessments were performed from the same tissue samples in 14 of 15 patients. For histological assessment, the density of collagen and elastin fibers was determined by combining high-resolution virtual imaging and computer-assisted digital image analysis. For biomechanical testing, uniaxial tension tests were performed to evaluate vaginal tissue stiffness at low (C0) and high (C1) deformation rates. RESULTS: Biomechanical testing highlights the hyperelastic behavior of the vaginal wall. At low strains (C0), vaginal tissue appeared stiffer when elastin density was low. We found a statistically significant inverse relationship between C0 and the elastin/collagen ratio (p = 0.048) in the lamina propria. However, at large strain levels (C1), no clear relationship was observed between elastin density or elastin/collagen ratio and stiffness, likely reflecting the large dispersion of the mechanical behavior of the tissue samples. CONCLUSION: Histological and biomechanical properties of the vaginal wall vary from patient to patient. This study suggests that elastin density deserves consideration as a relevant factor of vaginal stiffness in women with POP. [less ▲]

Detailed reference viewed: 39 (4 ULg)
Full Text
Peer Reviewed
See detailElasto-capillarity in insect fibrillar adhesion
Gernay, Sophie-Marie ULg; Federle, Walter; Lambert, Pierre et al

in Journal of the Royal Society, Interface (2016), 13(121),

The manipulation of microscopic objects is challenging because of high adhesion forces, which render macroscopic gripping strategies unsuitable. Adhesive footpads of climbing insects could reveal ... [more ▼]

The manipulation of microscopic objects is challenging because of high adhesion forces, which render macroscopic gripping strategies unsuitable. Adhesive footpads of climbing insects could reveal principles relevant for micro-grippers, as they are able to attach and detach rapidly during locomotion. However, the underlying mechanisms are still not fully understood. In this work, we characterize the geometry and contact formation of the adhesive setae of dock beetles (Gastrophysa viridula) by interference reflection microscopy. We compare our experimental results to the model of an elastic beam loaded with capillary forces. Fitting the model to experimental data yielded not only estimates for seta adhesion and compliance in agreement with previous direct measurements, but also previously unknown parameters such as the volume of the fluid meniscus and the bending stiffness of the tip. In addition to confirming the primary role of surface tension for insect adhesion, our investigation reveals marked differences in geometry and compliance between the three main kinds of seta tips in leaf beetles. [less ▲]

Detailed reference viewed: 7 (2 ULg)
Full Text
See detailElasto-inertial turbulence in polymeric flows
Terrapon, Vincent ULg; Dubief, Yves; Soria, Julio

Conference (2013, November 26)

The dynamics of elasto-inertial turbulence (EIT) is investigated numerically from the perspective of the coupling between polymer dynamics and flow structures. In particular, direct numerical simulations ... [more ▼]

The dynamics of elasto-inertial turbulence (EIT) is investigated numerically from the perspective of the coupling between polymer dynamics and flow structures. In particular, direct numerical simulations of channel flow with Reynolds numbers ranging from 1000 to 6000 are used to study the formation and dynamics of elastic instabilities and their effects on the flow. Based on the splitting of the pressure into inertial and polymeric contributions, it is shown that the trains of cylindrical structures around thin sheets of high polymer extension that are characteristics to elasto-inertial turbulence are mostly driven by polymeric contributions. [less ▲]

Detailed reference viewed: 27 (8 ULg)
Full Text
Peer Reviewed
See detailElasto-plastic material parameter identification by inverse methods: sensitivity matrix calculation
Cooreman, Steven; Bouffioux, Chantal ULg; Lecompte, David et al

in Proceedings of the SEM annual conference and exposition 2006 (2006)

Inverse methods offer a powerful tool for the determination of the elasto-plastic material properties. Contrary to standard tests, these methods can deal with heterogeneous stress and strain-fields which ... [more ▼]

Inverse methods offer a powerful tool for the determination of the elasto-plastic material properties. Contrary to standard tests, these methods can deal with heterogeneous stress and strain-fields which have a larger information contents and hence allow the simultaneous identification of several material parameters. Moreover, it is expected that the obtained material parameters are more accurate, since these heterogeneous deformation fields are much closer to those occurring in real (metal) forming operations. The principle of the inverse method for the identification of material parameters presented in this paper is to compare an experimentally measured strain field to that computed by a Finite Element (FE) model. The material parameters in the FE model are iteratively tuned in such a way that both strain fields match each other as close as possible. One of the building blocks in this identification procedure is the updating algorithm for the material parameters in the FE model. The key problem of this updating algorithm is the determination of the sensitivity matrix, which expresses the sensitivities of the strains with respect to the material parameters. This paper presents an analytical method for the calculation of this sensitivity matrix in case of simple tensile tests. [less ▲]

Detailed reference viewed: 92 (11 ULg)
Full Text
Peer Reviewed
See detailAn elasto-viscoplastic model for chalk including suction effects
Collin, Frédéric ULg; De Gennaro, Vincenzo; Delage, Pierre et al

in Toll, David (Ed.) Unsaturated Soils: Advances in Geo-Engineering (2008)

During the six years long Pasachalk project devoted to the mechanical behaviour of high porosity chalks from North Sea oilfields, the constitutive model Pasachalk (Collin et al., 2002) was proposed based ... [more ▼]

During the six years long Pasachalk project devoted to the mechanical behaviour of high porosity chalks from North Sea oilfields, the constitutive model Pasachalk (Collin et al., 2002) was proposed based on the Barcelona Basic Model (BBM) (Alonso et al., 1990). The approach was based on the similarities found between the oil-water interactions (oil and water being the non wetting and wetting fluid respectively) in oil reservoir chalk and the air-water interactions in unsaturated soils. This approach appeared to be relevant to in-terpret the subsidence of the seafloor during waterflooding operations for enhanced oil recovery that has been observed in North Sea oilfields (e.g. Ekofisk oilfield). Another important component of subsidence was then related to the creep behaviour of the multiphase chalk (De Gennaro et al., 2003). A modified Pasachalk model was proposed to account for time effects using the framework of Perzyna’s viscoplasticity (1964) but without considering suction effects. Based on available experimental results (Priol et al., 2007), a modified version of the viscoplastic Pasachalk model including suction effects is proposed in this paper. [less ▲]

Detailed reference viewed: 140 (8 ULg)
Peer Reviewed
See detailAn elasto-viscoplastic model for forging steel at high temperatures
Charles, J.-F.; Habraken, Anne ULg; Lecomte-Beckers, Jacqueline ULg

in Proceedings of NUMIFORM 98, Simulation of Materials Processing : Theory, Methods and Applications (1998)

Detailed reference viewed: 15 (4 ULg)
Full Text
Peer Reviewed
See detailElastocapillarity in Dock Beetle Adhesion
Gernay, Sophie-Marie ULg; Federle, Walter; Lambert, Pierre et al

Poster (2016, September)

Miniaturization is currently limited by our ability to manipulate micrometer-sized objects. Insect adhesion is an advantageous bio-inspired solution to this problem, although it is not fully understood ... [more ▼]

Miniaturization is currently limited by our ability to manipulate micrometer-sized objects. Insect adhesion is an advantageous bio-inspired solution to this problem, although it is not fully understood yet. Interference Reflection Microscopy images of the beetle Gastrophysa Viridula adhesive structures in contact with a smooth substrate were analyzed. The results were cross-linked with an analytical model of an elastic beam deflected by a liquid meniscus. By fitting the unknown model parameters to the experimental data, we obtained information about the elastic properties of the structures, the liquid volume in the bridge, and the resulting adhesion levels. [less ▲]

Detailed reference viewed: 12 (1 ULg)