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See detailOn the nature of the hard X-ray source IGR J2018+4043
Bykov, Andrei Mikhailovich; Krassilchtchikov, Alexandre Mikhailovich; Uvarov, Yuri Alexandrovich et al

in Astrophysical Journal (2006), 649(1, Part 2), 21-24

We found a very likely counterpart to the recently discovered hard X-ray source IGR J2018 + 4043 in the multiwavelength observations of the source field. The source, originally discovered in the 20-40 keV ... [more ▼]

We found a very likely counterpart to the recently discovered hard X-ray source IGR J2018 + 4043 in the multiwavelength observations of the source field. The source, originally discovered in the 20-40 keV band, is now confidently detected also in the 40-80 keV band, with a flux of (1.4 +/- 0.4) x 10(-11) ergs cm(-2) s(-1). A 5 ks Swift observation of the IGR J2018 + 4043 field revealed a hard pointlike source with an observed 0.5-10 keV flux of 3.4(-0.8)(+0.7) x 10(-12) ergs cm(-2) s(-1) (90% confidence level) at alpha = 20(h)18(m)38(s).55, delta = +40 degrees 41'00.4" (with a 4".2 uncertainty). The combined Swift-INTEGRAL spectrum can be described by an absorbed power-law model with photon index Gamma = 1.3 +/- 0.2 and N-H = 6.1(-2.2)(+3.3) x 10(22) cm(-2). In archival optical and infrared data we found a slightly extended and highly absorbed object at the Swift source position. There is also an extended VLA 1.4 GHz source peaked at a beamwidth distance from the optical and X-ray positions. The observed morphology and multiwavelength spectra of IGR J2018 + 4043 are consistent with those expected for an obscured accreting object, i.e., an AGN or a Galactic X-ray binary. The identification suggests possible connection of IGR J2018 + 4043 to the bright gamma-ray source GEV J2020 + 4023 detected by COS B and CGRO EGRET. [less ▲]

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See detailOn the nature of the spectral and photometric periodic variability of apparently single Wolf-Rayet stars
Morel, Thierry ULg

in The Observatory (1999), 119

Not Available

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See detailOn the necessity to consider varying parameters in the land subsidence computations
Dassargues, Alain ULg

in Barends, F. B. J.; Brouwer, F. J. J.; Schröder, F. H. (Eds.) Land Subsidence (Proc. of the Vth Int. Symp.) (1995)

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See detailOn the necessity to use three-dimensional groundwater models for describing impact of drought conditions on streamflow regimes
Dassargues, Alain ULg; Maréchal, J. C.; Carabin, Guy et al

in Hydrological Extremes : Understanding, Predicting, Mitigating (1999)

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See detailOn the Number of Abelian Bordered Words
Rampersad, Narad; Rigo, Michel ULg; Salimov, Pavel ULg

in Lecture Notes in Computer Science (2013), 7907

In the literature, many bijections between (labeled) Motzkin paths and various other combinatorial objects are studied. We consider abelian (un)bordered words and show the connection with irreducible ... [more ▼]

In the literature, many bijections between (labeled) Motzkin paths and various other combinatorial objects are studied. We consider abelian (un)bordered words and show the connection with irreducible symmetric Motzkin paths and paths in Z not returning to the origin. This study can be extended to abelian unbordered words over an arbitrary alphabet and we derive expressions to compute the number of these words. In particular, over a 3-letter alphabet, the connection with paths in the triangular lattice is made. Finally, we study the lengths of the abelian unbordered factors occurring in the Thue--Morse word. [less ▲]

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See detailOn the numerical damping of time integrators for coupled mechatronic systems
Bruls, Olivier ULg; Golinval, Jean-Claude ULg

in Computer Methods in Applied Mechanics & Engineering (2008), 197(6-8), 577-588

The generalized-alpha time integrator is considered for the simulation of mechatronic systems. In this context, the fundamental concept of numerical damping is analysed for coupled sets of first and ... [more ▼]

The generalized-alpha time integrator is considered for the simulation of mechatronic systems. In this context, the fundamental concept of numerical damping is analysed for coupled sets of first and second-order differential-algebraic equations. First, it appears that the algebraic variables do not influence the spectral properties of the dynamic variables. Second, we demonstrate that the coupling between the dynamic variables does not influence the high-frequency spectral response, so that the numerical damping can be determined as usual from elementary characteristic polynomials. Those results are exploited to assess the stability properties of the scheme and to select an algorithm with optimal damping properties. [less ▲]

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See detailOn the numerical integration of an advanced Gurson model
Ben Bettaieb, Mohamed ULg; Lemoine, Xavier; Duchene, Laurent ULg et al

in International Journal for Numerical Methods in Engineering (2011), 85(8), 1049-1072

This article is focused on a new extended version of Gurson's model (J. Eng. Mater. Technol. 1977; 99:2–15), its numerical integration scheme and its consistent tangent matrix being within an FE code ... [more ▼]

This article is focused on a new extended version of Gurson's model (J. Eng. Mater. Technol. 1977; 99:2–15), its numerical integration scheme and its consistent tangent matrix being within an FE code. First, this new advanced Gurson model is proposed, which is an extension of the original to take into account plastic anisotropy and mixed (isotropic+kinematic) hardening. In this paper, only the growth phase of cavities is considered (the nucleation of new voids is ignored). Second, a new numerical algorithm for the integration of this new Gurson model is presented. The algorithm is implicit in all variables and is unconditionally stable. This algorithm is generic and could be used for other anisotropic yield functions and other hardening laws. Third, the consistent tangent matrix is computed in an explicit way by exact linearization of the constitutive equations. To check its efficiency and robustness, the proposed integration algorithm is compared, under some simplified assumptions and choices, with the algorithms of Aravas (Int. J. Numer. Meth. Engng 1987; 24:1395–1416) and Kojic (Int. J. Numer. Meth. Engng 2002; 53(12):2701–2720). The performance of the developed consistent modulus, compared to other techniques for the computation of the tangent matrix is assessed. The paper ends with numerical simulations of tensile tests on homogeneous and notched specimens. [less ▲]

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See detailOn the numerical integration of rate independent single crystal behavior at large strain
Ben Bettaieb, Mohamed; Débordes, Olivier; Dogui, Abdelwaheb et al

in International Journal of Plasticity (2012), 32-33

This paper presents a new numerical algorithm for the integration of the constitutive equations of a single crystal for finite rate-independent elastoplastic strains. The algorithm addressed in this paper ... [more ▼]

This paper presents a new numerical algorithm for the integration of the constitutive equations of a single crystal for finite rate-independent elastoplastic strains. The algorithm addressed in this paper is dedicated to face-centered-cubic (FCC) crystal structures. Its first feature is a much more efficient and more accurate integration scheme of the constitutive equations compared to previous attempts. This scheme is based on a fully implicit integration procedure, yet it may be transformed easily into an explicit scheme. Determining the set of active slip systems is performed by the use of a combinatorial search procedure, and the determination of the slip rates of the different active slip systems is based on the fixed point method. The second feature of this algorithm stems from the original method used to solve the ambiguity of the possible non-uniqueness of the set of active slip systems. A robust method, based on a small positive perturbation of the critical shear stresses, is proposed to overcome this difficulty. It is worth mentioning that the algorithm developed in this paper is not limited to one particular hardening law or to FCC crystal structures. Rather, it can be used and extended to various hardening laws and crystal structures (e.g. BCC or HCP. . .) in a straightforward manner. The authors demonstrate the performance of the proposed algorithm and illustrate its accuracy and efficiency through various numerical simulations at the single crystal and polycrystal scales. The predicted results obtained from those simulations were compared with those obtained using other numerical techniques and algorithms (i.e., a pseudo-inversion technique and an explicit algorithm). Our numerical predictions are also compared with some numerical and experimental results from other papers. The response of the polycrystal was computed by using the proposed algorithm combined with Taylor’s homogenization scheme, which is used to compute the overall polycrystalline behavior. The paper ends with a statistical study of the influence of the perturbation technique on the response prediction for a single crystal and a polycrystal. [less ▲]

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See detailOn the numerical modeling of shear banding around an excavation
Collin, Frédéric ULg; Li, Xiang Ling; Lambarki, A. et al

Conference (2005)

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See detailOn the numerical modelling of shear banding around an excavation
Collin, Frédéric ULg; Li, X.L.; Lambarki, A. et al

Conference (2005)

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See detailOn the numerical modelling of shear banding around an excavation
Collin, Frédéric ULg; Lambarki, A.; Charlier, Robert ULg et al

Conference (2005)

For an underground storage of nuclear waste, it is necessary to minimize the excavation damage zone (EDZ) that could be a higher permeability zone. This paper deals with the FE modelling of the EDZ extent ... [more ▼]

For an underground storage of nuclear waste, it is necessary to minimize the excavation damage zone (EDZ) that could be a higher permeability zone. This paper deals with the FE modelling of the EDZ extent during tunnelling. A Drucker – Prager law with cohesion strain softening is used. Results show a shear banding around the excavation. Its extent and the tunnel convergence are highly dependent on the hydraulic boundary condition within the tunnel (imposed pore pressure – suction or unilateral flow condition). [less ▲]

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See detailOn the numerical simulation of sheet metal blanking process
Canales Cardenas, Cristian ULg; Bussetta, Philippe ULg; Habraken, Anne ULg et al

Conference (2014)

One of the most widely used cutting techniques in sheet metal forming processes for mass production is the blanking process. In this process, a metallic sheet is placed between a die and a blankholder ... [more ▼]

One of the most widely used cutting techniques in sheet metal forming processes for mass production is the blanking process. In this process, a metallic sheet is placed between a die and a blankholder, and is then cut by the action of a punch which moves downward. The quality of the final product is directly linked to the resulting shape of the cut edge. Due to the complexity of the separation step, the set-up of the blanking process in practice is often driven by empirical knowledge. Thus, an accurate numerical tool is extremely desirable to optimize the setting parameters of this technique and will lead to a better understanding of the entire process. The numerical approach must be able to deal with three main issues involved in blanking: large and localized deformation, friction and contact, and ductile fracture. Furthermore, due to requirements of mass production the punch velocity is normally high and the effects of the strain rate must also be considered. Several approaches have been developed in order to model this cutting process but its accuracy still presents some numerical challenges. [less ▲]

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See detailOn the O(1) Solution of Multiple-Scattering Problems
Geuzaine, Christophe ULg; Bruno, O.; Reitich, F.

in IEEE Transactions on Magnetics (2005), 41(5), 1488-1491

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See detailOn the O(1) Solution of Multiple-Scattering Problems
Geuzaine, Christophe ULg; Bruno, O.; Reitich, F.

in Proceedings of the 11th IEEE Conference on Electromagnetic Field Computation (CEFC'2004) (2004)

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See detailOn the observability of resonant structures in planetesimal disks due to planetary migration
Reche, R.; Beust, H.; Augereau, J.-C. et al

in Astronomy and Astrophysics (2008), 480

Context: The observed clumpy structures in debris disks are commonly interpreted as particles trapped in mean-motion resonances with an unseen exo-planet. Populating the resonances requires a migrating ... [more ▼]

Context: The observed clumpy structures in debris disks are commonly interpreted as particles trapped in mean-motion resonances with an unseen exo-planet. Populating the resonances requires a migrating process of either the particles (spiraling inward due to drag forces) or the planet (moving outward). Because the drag time-scale in resolved debris disks is generally long compared to the collisional time-scale, the planet migration scenario might be more likely, but this model has so far only been investigated for planets on circular orbits. Aims: We present a thorough study of the impact of a migrating planet on a planetesimal disk, by exploring a broad range of masses and eccentricities for the planet. We discuss the sensitivity of the structures generated in debris disks to the basic planet parameters. Methods: We perform many N-body numerical simulations, using the symplectic integrator SWIFT, taking into account the gravitational influence of the star and the planet on massless test particles. A constant migration rate is assumed for the planet. Results: The effect of planetary migration on the trapping of particles in mean motion resonances is found to be very sensitive to the initial eccentricity of the planet and of the planetesimals. A planetary eccentricity as low as 0.05 is enough to smear out all the resonant structures, except for the most massive planets. The planetesimals also initially have to be on orbits with a mean eccentricity of less than than 0.1 in order to keep the resonant clumps visible. Conclusions: This numerical work extends previous analytical studies and provides a collection of disk images that may help in interpreting the observations of structures in debris disks. Overall, it shows that stringent conditions must be fulfilled to obtain observable resonant structures in debris disks. Theoretical models of the origin of planetary migration will therefore have to explain how planetary systems remain in a suitable configuration to reproduce the observed structures. [less ▲]

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See detailOn the observability of the quark orbital angular momentum distribution
Courtoy, Aurore ULg; Goldstein, Gary R.; Hernandez, J. Osvaldo Gonzalez et al

in Physics Letters B (2014), 731(0), 141-147

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See detailOn the occurrence of (iso-)dolichantoside in Strychnos mellodora
Quarré, Marie-Noëlle; Tits, Monique ULg; Wauters, Jean-Noël ULg et al

Poster (1994, March)

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See detailOn the optimisation of the mechanical properties of two aluminium-alloyed multiphase TRIP-assisted steels
Mertens, Anne ULg; Jacques, Pascal J.; Harlet, Philippe et al

in De Cooman, Bruno C. (Ed.) Proccedings of the International Conference on TRIP-Aided High Strength Ferrous Alloys (2002, June)

Aluminium-alloyed multiphase TRIP-assisted steels have been recently developed, so as to get rid of the disdavantages related to the high silicon contents classically used so far in TRIP-assisted steels ... [more ▼]

Aluminium-alloyed multiphase TRIP-assisted steels have been recently developed, so as to get rid of the disdavantages related to the high silicon contents classically used so far in TRIP-assisted steels. It has been shown that aluminium has a stronger ferritising effect than silicon and that it is slightly less efficient as far as austenite retention is concerned. A careful selection of the aluminium content and of the processing conditions is thus of primary importance in order to optimise the mechanical properties. The present study aims at determining the optimal heat treatment conditions leading to enhanced mechanical properties for two low aluminium-alloyed grades containing with mass contents of 0.12% C, 1.5% Mn and 0.5% Al or 1.0% Al, respectively. The microstructures generated during the heat treatment were assessed using SEM, X-ray diffraction and Mössbauer spectrometry. The mechanical properties were evaluated by uniaxial tensilte testing and the strain-hardening behaviour was characterised by means of an incremental strain-hardening exponent. The relations between the observed microstructures and the mechanical properties were discussed and, as a consequence, the importance of a careful control of the isothermal bainitic holding was highlighted. [less ▲]

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See detailOn the origin and systematics of the northern African wood mouse (Apodemus sylvaticus) populations: a comparative study of mtDNA restriction patterns
Libois, Roland ULg; Michaux, Johan ULg; Ramalhinho, M. G. et al

in Canadian Journal of Zoology (2001), 79(8), 1503-1511

Conflicting hypotheses have been formulated regarding the origin of wood mouse (Apodemus sylvaticus) populations in northern Africa. In this study, the mtDNA restriction patterns of mice (n = 28 ... [more ▼]

Conflicting hypotheses have been formulated regarding the origin of wood mouse (Apodemus sylvaticus) populations in northern Africa. In this study, the mtDNA restriction patterns of mice (n = 28) collected in Tunisia and Morocco are compared with those of representatives from southern Europe (n = 102). The neighbour-joining tree confirms the existence of the three lineages previously found in the Mediterranean area: western, Tyrrhenian-Balkan, and Sicilian. The western group is isolated from the two others, with bootstrap values of 89 and 95%. Northern African patterns are included in the western group. Their variability is low, the same pattern being shared by five Tunisian and all Moroccan animals (n = 18), caught either in the north of the country (Cap Spartel) or in the south (Marrakech). This implies that northern African wood mouse populations have a southwestern European origin and that their presence in the region is probably recent, which corresponds to both paleontological data and the hypothesis of anthropogenic introduction. [less ▲]

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See detailOn the origin of bacterial resistance to penicillin: comparison of a beta-lactamase and a penicillin target
Kelly, Judith A.; Dideberg, Otto; Charlier, Paulette ULg et al

in Science (1986), 231

Structural data are now available for comparing a penicillin target enzyme, the D-alanyl-D-alanine-peptidase from Streptomyces R61, with a penicillin-hydrolyzing enzyme, the beta-lactamase from Bacillus ... [more ▼]

Structural data are now available for comparing a penicillin target enzyme, the D-alanyl-D-alanine-peptidase from Streptomyces R61, with a penicillin-hydrolyzing enzyme, the beta-lactamase from Bacillus licheniformis 749/C. Although the two enzymes have distinct catalytic properties and lack relatedness in their overall amino acid sequences except near the active-site serine, the significant similarity found by x-ray crystallography in the spatial arrangement of the elements of secondary structure provides strong support for earlier hypotheses that beta-lactamases arose from penicillin-sensitive D-alanyl-D-alanine-peptidases involved in bacterial wall peptidoglycan metabolism. [less ▲]

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