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See detailMeasurements on magnetized GdBCO pellets subjected to small transverse ac magnetic fields at very low frequency: Evidence for a slowdown of the magnetization decay
Fagnard, Jean-François ULg; Kirsch, Sébastien; Morita, Mitsuru et al

in Physica C: Superconductivity (2015), 512

Due to their ability to trap large magnetic inductions, superconducting bulk materials can be used as powerful permanent magnets. The permanent magnetization of such materials, however, can be ... [more ▼]

Due to their ability to trap large magnetic inductions, superconducting bulk materials can be used as powerful permanent magnets. The permanent magnetization of such materials, however, can be significantly affected by the application of several cycles of a transverse variable magnetic field. In this work, we study, at T = 77 K, the long term influence of transverse ac magnetic fields of small amplitudes (i.e. much smaller than the full penetration field) on the axial magnetization of a bulk single grain superconducting GdBCO pellet over a wide range of low frequencies (1 mHz–20 Hz). Thermocouples are placed against the pellet surface to probe possible self-heating of the material during the experiments. A high sensitivity cryogenic Hall probe is placed close to the surface to record the local magnetic induction normal to the surface. The results show first that, for a given number of applied triangular transverse cycles, higher values of dBapp/dt induce smaller magnetization decays. An important feature of practical interest is that, after a very large number of cycles which cause the loss of a substantial amount of magnetization (depending on the amplitude and the frequency of the field), the rate of the magnetization decay goes back to its initial value, corresponding to the relaxation of the superconducting currents due to flux creep only. In the amplitude and frequency range investigated, the thermocouples measurements and a 2D magneto-thermal modelling show no evidence of sufficient self-heating to affect the magnetization so that the effect of the transverse magnetic field cycles on the trapped magnetic moment is only attributed to a redistribution of superconducting currents in the volume of the sample and not to a thermal effect. [less ▲]

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See detailPartenariats entre services publics de l'emploi et opérateurs privés. Une question de confiance?
Remy, Céline ULg

Scientific conference (2015, May 13)

À l’heure des politiques d’activation des demandeurs d’emploi et d’un taux de chômage élevé, il semble tout particulièrement intéressant d’interroger les réformes institutionnelles des services publics de ... [more ▼]

À l’heure des politiques d’activation des demandeurs d’emploi et d’un taux de chômage élevé, il semble tout particulièrement intéressant d’interroger les réformes institutionnelles des services publics de l’emploi (SPE), notamment en matière de partenariats. Fin des années 90, la Commission européenne invite les SPE à établir des collaborations avec des organismes d’insertion socioprofessionnelle. Les SPE doivent déléguer une partie de leur mission d’accompagnement des demandeurs d’emploi à des opérateurs privés marchands et non-marchands. Des partenariats publics-privés voient progressivement le jour. Leur objectif est la mise en place de projets de formation et d’accompagnement à destination des demandeurs d’emploi en vue de la réinsertion de ceux-ci dans un emploi stable et de qualité. Perdant leur monopole en matière d’accompagnement, les SPE se repositionnent sur le marché de l’emploi en tant qu’« institution régulatrice » de ce marché. Déléguer leur mission aux opérateurs privés engendre nécessairement la question de la confiance. Comment les SPE accordent-ils leur confiance à ces organismes ? Une étude menée auprès de trois services publics de l’emploi, situés en Belgique et en Suisse, nous a permis d’analyser en profondeur les collaborations entre l’Office de l’Emploi et ses prestataires de service. La recherche porte tout particulièrement sur la construction, la vie et les effets du partenariat en termes de confiance. [less ▲]

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See detailTransport of Bose-Einstein Condensates through Aharonov-Bohm rings
Chrétien, Renaud ULg; Dujardin, Julien ULg; Petitjean, Cyril ULg et al

Poster (2015, May 13)

We study the one-dimensional (1D) transport properties of an ultracold gas of Bose-Einstein condensed atoms through Aharonov-Bohm (AB) rings. Our system consists of a Bose-Einstein condensate (BEC) that ... [more ▼]

We study the one-dimensional (1D) transport properties of an ultracold gas of Bose-Einstein condensed atoms through Aharonov-Bohm (AB) rings. Our system consists of a Bose-Einstein condensate (BEC) that is outcoupled from a magnetic trap into a 1D waveguide which is made of two semi-infinite leads that join a ring geometry exposed to a magnetic flux φ. We specifically investigate the effects of a small atom-atom contact interaction strength on the AB oscillations. The main numerical tools that we use for this purpose are a mean-field Gross-Pitaevskii (GP) description and the truncated Wigner (tW) method. The latter allows for the description of incoherent transport and corresponds to a classical sampling of the evolution of the quantum bosonic many-body state through effective GP trajectories. We find that resonant transmission peaks move with an increasing interaction strength and can be suppressed for sufficiently strong interaction. We also observe that the coherent transmission blockade due to destructive interference at the AB flux φ = π is very robust with respect to the interaction strength. [less ▲]

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See detailFlemish nationalism and hip-hop in Belgium Politics v/s music between ethnicity and class
Mazzola, Alessandro ULg

Scientific conference (2015, May 12)

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See detailAnalytical strategies for ultra-trace measurement of dioxins and related compounds in biological matrices
L'Homme, Benjamin ULg

Doctoral thesis (2015)

The human exposure to persistent organic pollutants (POPs) is a concern since these compounds are ubiquitous in the environment. This class of compounds group different families such as the ... [more ▼]

The human exposure to persistent organic pollutants (POPs) is a concern since these compounds are ubiquitous in the environment. This class of compounds group different families such as the polychlorodibenzo-p-dioxins (PCDDs), the polychlorodibenzofurans (PCDFs), the polychlorinated biphenyls (PCBs), the organochlorine pesticides (OCPs), and the halogenated flame-retardants (HFRs). Their use, their release in the environment, their presence in foodstuffs, as well as in various goods on the market are mostly regulated through international conventions, like the Stockholm convention on POPs, and at the European and national levels. Despite the proactive approach in order to reduce the overall exposure to POPs, levels of contaminants (even banned) are still found in the environment and in the human body. In this thesis, we developed several methods of analysis of POPs in different samples. The first was a confirmatory method for PCDD/Fs and PCBs analysis in food and feed following a new European Regulation No 709/2014 that recently allowed the use of gas chromatography (GC) coupled to triple quadrupole mass spectrometry (GC-QQQMS/MS) for this purpose. We fully validated the method on vegetable oil matrix around the maximum level of 1.50 ng WHO2005TEQ/kg. We showed that all analytical criteria, specific to this instrumentation, laid down by the Regulation were met, which indicates that the QQQMS/MS can successfully be used in the legal context for confirmatory purposes and could be an alternative to high-resolution sector field mass spectrometry (HRMS) in this context. The proper establishment of limits of quantitation was a key point in the discussion along with other analytical criteria proposed in the European Regulation, as new interpretations were necessary for the use of triple quadrupole mass spectrometry due to its different features from the HRMS. In addition, we developed in parallel a method for the analysis of Dechloranes in food. The measurement of ultra-trace levels of compounds from this emerging class of flame-retardants was possible after optimization of the injections parameters by means of experimental design, and of fragmentation pathways. Eventually, we reported relatively low levels in various food matrices and preliminary data about the significance of this route of exposure for humans. Besides food analysis, we developed a screening method to quickly assess levels of contaminants in human blood, involving a minimally invasive sampling technique and a couple of drops of blood. The instrumentation was first based on cryogenic zone compression (CZC) hyphenated to high-resolution time of flight mass spectrometry (HRTOFMS) applied to the analysis of two markers of exposure in regular dried-blood spots (DBS) typically used for newborn sampling. The second approach was based on GC-QQQMS/MS applied to the analysis of a broader range of OCPs and NDL-PCBs (30 analytes) in 40 µL blood. The blood was however collected using a novel Volumetric Absorptive MicroSampling (VAMS) method, directly inspired by the DBS but offering a control on the volume of blood sampled, hence opening the door to quantitation. The sample preparation of the VAMS dried sample was miniaturized and only 2 mL of solvents were necessary to prepare a sample, which makes it environmentally friendly. The focus was especially drawn to maximize the sensitivity via the optimization of the ionization energy and the electron multiplier voltage in order to reach appropriate low limits of quantitation. In this context of ultra-low volume of blood, background levels arose as the limitation of the method owing to the small signals coming from samples and closing the gap with blanks. Nevertheless, this patient-friendly approach is perfectly suitable for fast screening of population and could be useful in the context of UNEP campaigns where samples are hardly collected. [less ▲]

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See detailTraduction et représentation politique : quelques éléments pour une genèse de leur rapport et de leur pertinence comme outils d’analyse politique
Smette, Bernard ULg

Conference (2015, May 08)

J’interrogerai la problématique du rapport de la traduction à la politique à partir de la notion de représentation politique, telle que thématisée par le théoricien argentin de l’analyse de discours ... [more ▼]

J’interrogerai la problématique du rapport de la traduction à la politique à partir de la notion de représentation politique, telle que thématisée par le théoricien argentin de l’analyse de discours, Ernesto LACLAU. Je commencerai très brièvement par resituer le processus de représentation dans le champ politique actuel. Cette re-contextualisation permettra de montrer que les notions de « représentation » et de « politique » entretiennent un rapport privilégié, mais qui ne se limite pas uniquement à sa forme contemporaine la plus répandue, symbolisée par nos institutions et principes politiques, tels le régime parlementaire ou encore l’élection. Je passerai alors au cœur de ma communication en dessinant la proximité conceptuelle et fonctionnelle de la traduction et de la représentation. Je me baserai, pour ce faire, sur les développements qu’Ernsto LACLAU a proposés de cette dernière, ainsi que sur quelques développements de Jean-René LADMIRAL et Willard Van Orman QUINE au sujet de la traduction. Je montrerai notamment (1) en quoi la conception de la représentation que propose LACLAU est un outil d’analyse pertinent de la politique, mais surtout (2) en quoi cette conception de la représentation est guidée par des processus traductifs. Je tenterai enfin, en guise de conclusion, de montrer en quoi l’on peut dégager de ce qui précède une perspective d’analyse supplémentaire, voire innovante, de l’articulation entre traduction, représentation et politique. [less ▲]

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See detailLe confesseur du Prince dans les Pays-Bas espagnols (1598-1659): une fonction, des individus.
Pirlet, Pierre-François ULg

Doctoral thesis (2015)

Cette thèse envisage, à la cour de Bruxelles (1598-1659), les rapports entre les pouvoirs séculiers et religieux au travers de la figure nodale du confesseur du Prince.

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See detailLatin as literary Language in Constantinople ca. 400-700
Rochette, Bruno ULg

Scientific conference (2015, May 06)

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See detailDensité et complexité du lien fraternel: le contexte de la parentification
Haxhe, Stéphanie ULg

Conference given outside the academic context (2015)

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See detail'Een lent van vaerzen' als letterkundig spiegelkabinet
Steyaert, Kris ULg

in Arabesken: Tijdschrift van het Louis Couperus Genootschap (2015)

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See detailValid inequalities for the single arc design problem with set-ups
Agra, Agostinho; Doostmohammadi, Mahdi; Louveaux, Quentin ULg

in Discrete Optimization (2015), 16

We consider a mixed integer set which generalizes two well-known sets: the single node fixed- charge network set and the single arc design set. Such set arises as a relaxation of feasible sets of general ... [more ▼]

We consider a mixed integer set which generalizes two well-known sets: the single node fixed- charge network set and the single arc design set. Such set arises as a relaxation of feasible sets of general mixed integer problems such as lot-sizing and network design problems. We derive several families of valid inequalities that, in particular, generalize the arc resid- ual capacity inequalities and the flow cover inequalities. For the constant capacitated case we provide an extended compact formulation and give a partial description of the convex hull in the original space which is exact under a certain condition. By lifting some basic inequalities we provide some insight on the difficulty of obtaining such a full polyhedral description for the constant capacitated case. Preliminary computational results are presented. [less ▲]

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See detailTesting of a Spacecraft Structure with Non-Smooth Nonlinearities
Renson, Ludovic ULg; Noël, Jean-Philippe ULg; Kerschen, Gaëtan ULg

Conference (2015, May)

The dynamics of the SmallSat, a real-life spacecraft possessing a complex isolation device with multiple nonsmooth nonlinearities is investigated. Experiments show that nonlinearities induce modal ... [more ▼]

The dynamics of the SmallSat, a real-life spacecraft possessing a complex isolation device with multiple nonsmooth nonlinearities is investigated. Experiments show that nonlinearities induce modal interactions between modes with non-commensurate linear frequencies. A model of the structure with a simplified description of the nonlinear connections is first built using techniques available in industry. Numerical continuation is then exploited to compute nonlinear normal modes and uncover interaction phenomena that can jeopardize the structural integrity. [less ▲]

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See detailPerformance-Based Aid: Why it will probably not meet promises
Paul, Elisabeth ULg

in Development Policy Review (2015), 33(3),

Performance-based aid (PBA) is increasingly advocated as a way to improve development aid effectiveness through resolving incentive issues inherent in aid relationships. Some donors use PBA together with ... [more ▼]

Performance-based aid (PBA) is increasingly advocated as a way to improve development aid effectiveness through resolving incentive issues inherent in aid relationships. Some donors use PBA together with performance-based financing arrangements within partner countries. Expectations from PBA are high – yet, while its rationale may look appealing, it is grounded on a restrictive model and flawed when taking account of real-world context. A number of problems associated to PBA have already been advanced as jeopardising its success. More fundamentally, one may question the mere appropriateness of PBA to provide incentives all along the chain from recipient governments to those who are supposed to produce results. Thus believing that PBA can have a mechanistic trickle-down incentive effect seems an illusion. [less ▲]

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