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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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See detailAdapting Nitrogen management to the increasing climatic uncertainty
Dumont, Benjamin ULg; Basso, Bruno; Bodson, Bernard ULg et al

in Shirmohammadi, Adel; Bosch, David; Muñoz-Carpena, Rafa (Eds.) Proceedings of the 1st ASABE Climate Change Symposium - Adaptation and Mitigation (2015, May)

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See detailLinear and propeller-like fluoro-isoindigo based donor–acceptor small molecules for organic solar cells
Ouhib, Farid ULg; Tomassetti, Mirco ULg; Dierckx, Wauter et al

in Organic Electronics (2015), 20

Two donor–acceptor type fluoro-isoindigo based small molecule semiconductors are syn- thesized and their optical, electrochemical, thermal, and charge transport properties are investigated. The two ... [more ▼]

Two donor–acceptor type fluoro-isoindigo based small molecule semiconductors are syn- thesized and their optical, electrochemical, thermal, and charge transport properties are investigated. The two molecular chromophores differ by their architecture, linear (M1) vs propeller-like (M2). Both molecules present a broad absorption in the visible range and a low optical HOMO–LUMO gap (?1.6 eV). AFM images of solution-processed thin films show that the trigonal molecule M2 forms highly oriented fibrils after a few seconds of solvent vapor annealing. The materials are evaluated as electron donor components in bulk heterojunction organic solar cells using PC61BM as the electron acceptor. The devices based on the propeller-like molecule M2 exhibit a high open-circuit voltage (around 1.0 V) and a power conversion efficiency of 2.23%. [less ▲]

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See detailA comparison of within-season yield prediction algorithms based on crop model behaviour analysis
Dumont, Benjamin ULg; Basso, Bruno; Leemans, Vincent ULg et al

in Agricultural and Forest Meteorology (2015), 204

The development of methodologies for predicting crop yield, in real-time and in response to different agro-climatic conditions, could help to improve the farm management decision process by providing an ... [more ▼]

The development of methodologies for predicting crop yield, in real-time and in response to different agro-climatic conditions, could help to improve the farm management decision process by providing an analysis of expected yields in relation to the costs of investment in particular practices. Based on the use of crop models, this paper compares the ability of two methodologies to predict wheat yield (Triticum aestivum L.), one based on stochastically generated climatic data and the other on mean climate data. It was shown that the numerical experimental yield distribution could be considered as a log-normal distribution. This function is representative of the overall model behaviour. The lack of statistical differences between the numerical realisations and the logistic curve showed in turn that the Generalised Central Limit Theorem (GCLT) was applicable to our case study. In addition, the predictions obtained using both climatic inputs were found to be similar at the inter and intra-annual time-steps, with the root mean square and normalised deviation values below an acceptable level of 10% in 90% of the climatic situations. The predictive observed lead-times were also similar for both approaches. Given (i) the mathematical formulation of crop models, (ii) the applicability of the CLT and GLTC to the climatic inputs and model outputs, respectively, and (iii) the equivalence of the predictive abilities, it could be concluded that the two methodologies were equally valid in terms of yield prediction. These observations indicated that the Convergence in Law Theorem was applicable in this case study. For purely predictive purposes, the findings favoured an algorithm based on a mean climate approach, which needed far less time (by 300-fold) to run and converge on same predictive lead time than the stochastic approach. [less ▲]

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See detailRocking behaviour of simple unreinforced load-bearing masonry walls includings soundproofing rubber layers
Mordant, Christophe ULg; Denoël, Vincent ULg; Degée, Hervé

in Proceedings of 5th ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (2015, May)

This paper compares experimental measurements with predictions of different rocking models. These comparisons are carried out on the base of recent experimental results obtained by shake-table tests of ... [more ▼]

This paper compares experimental measurements with predictions of different rocking models. These comparisons are carried out on the base of recent experimental results obtained by shake-table tests of four simple unreinforced load-bearing clay masonry walls that have exhibited a significant rocking behaviour for the highest acceleration inputs. In a first stage, the simple model proposed by Housner is used after slight modifications needed to properly consider the actual mass distribution. Two parameters are identified as governing the model response, namely the criterion defining the initiation of motion and the restitution coefficient. Then, a two stacked blocks model is developed and solved by an event-driven strategy. This two-block model is intended to allow a better description of the behaviour of tested specimens through a more precise modelling of the additional mass. Finally, the pres-ence of rubber layers positioned at the top and bottom of two of the tested walls with the pur-pose of improving their acoustic behaviour required the development of an updated rocking model with viscous and flexible interfaces at the base of the wall and between the two stacked blocks. The properties of these interfaces are deduced from experimental data and their sig-nificant influence on the response is evidenced. [less ▲]

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See detailLes réseaux scientifiques du Roi en Belgique
Pirot, Pascal ULg

Conference (2015, April 30)

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See detailRepresenting a Minority Group in Multinational Federal Systems: Career Patterns in Catalonia, Scotland and Wallonia
Dodeigne, Jérémy ULg

Doctoral thesis (2015)

Dans nos démocraties représentatives, comprendre « qui » gouverne et plus précisément « comment » et « pourquoi » certains accèdent aux positions de pouvoir a toujours été un enjeu démocratique majeur ... [more ▼]

Dans nos démocraties représentatives, comprendre « qui » gouverne et plus précisément « comment » et « pourquoi » certains accèdent aux positions de pouvoir a toujours été un enjeu démocratique majeur. Avec les processus de régionalisation et de fédéralisation observés à travers le monde, cette question s’est complexifiée en raison de la multiplication des lieux de décision politique. Dans de nombreux pays, les représentants politiques évoluent désormais dans des systèmes multi-niveaux. L’une des conséquences directes de ces réformes institutionnelles est la transformation des carrières parlementaires, particulièrement dans les régions minoritaires des états plurinationaux comme la Belgique, l’Espagne et le Royaume-Uni. L’objectif de cette recherche doctorale est double. D’une part, elle cherche à définir l’orientation régionale et/ou nationale qui caractérise la carrière des élus depuis l’instauration des assemblées régionales. D’autre part, elle vise à identifier les facteurs qui expliquent l’émergence de ces différents types de carrières. À cette fin, la thèse développe une étude comparée de la Catalogne, de l’Écosse et de la Wallonie qui combine analyses quantitatives et qualitatives. Une des conclusions majeures de cette recherche est que le niveau de pouvoir régional est devenu une arène politique de plus en plus attractive – voire prédominante pour certains acteurs. Toutefois, contrairement à ce qui fut suggéré par des études antérieures, les parlements nationaux espagnol, britannique et belge continuent d’être des arènes politiques attractives pour les élus catalans, écossais et wallons. [less ▲]

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See detailExperimental study and phenomenological modeling of the quasi-static mechanical behavior of Ti6Al4V at room temperature
Gilles, Gaëtan ULg

Doctoral thesis (2015)

The work aims to characterize the quasi-static mechanical behavior of the Ti6Al4V titanium alloy at room temperature and to describe it by a phenomenological model. The thesis is divided in four parts ... [more ▼]

The work aims to characterize the quasi-static mechanical behavior of the Ti6Al4V titanium alloy at room temperature and to describe it by a phenomenological model. The thesis is divided in four parts. The first one presents a literature review of the basic properties of titanium and its alloys (crystal structure, classification, deformation mechanisms), then it focuses on the specific mechanical features of Ti6Al4V. It also proposes a state of art in the field of the phenomenological constitutive laws used to model the mechanical behaviors of metals. The second part deals with the experimental campaign conducted on a 0.6 mm thick Ti6Al4V sheet. The devices and the tests are first described before giving the test results. The campaign includes experiments with monotonic and complex strain paths (tension, compression, simple shear, plane strain, Bauschinger tests, deep-drawing processes, layer compression tests). The experimental results show that the material displays anisotropy in yield stress, r-ratios and hardening, as well as a strength differential effect between tension and compression. The third part describes the implementation of the yield criteria CPB06exn in the non-linear finite element code LAGAMINE developed in MSM team. These criteria are selected to model the yield locus of Ti6Al4V since they are able to take into account both the anisotropy and the tension-compression asymmetry exhibited by the alloy. Several parameter identifications are performed using the classical simulated annealing algorithm. They determine that CPB06ex2 is required to represent the yield surface. The criterion is next associated to different hardening formulations: (1) Voce isotropic law; (2) mixed Voce isotropic – Armstrong-Frederick kinematic law; (3) model taking into account the evolution of the yield locus shape with the deformation. The identification of the hardening parameters is achieved from the monotonic and Bauschinger tests either by inverse method, or by the simulated annealing method. The last part of the thesis proposed a validation of the different modelings in the case of the layer compression tests and the deep-drawing processes. [less ▲]

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See detailEffect of nanocrystalline structure on magnetocaloric effect in manganite composites (1/3)La0.7Ca0.3MnO3/(2/3)La0.8Sr0.2MnO3
Pękała, M; Pękała, K; Drozd, V et al

in Journal of Alloys & Compounds (2015), 629

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See detailGraded-commutative nonassociative algebras: higher octonions and Krichever-Novikov superalgebras; their structures, combinatorics and non-trivial cocycles.
Kreusch, Marie ULg

Doctoral thesis (2015)

This dissertation consists of two parts. The first one is the study of a series of real (resp. complex) noncommutative and nonassociative algebras $\bbO_{p,q}$ (resp. $\bbO_{n}$) generalizing the algebra ... [more ▼]

This dissertation consists of two parts. The first one is the study of a series of real (resp. complex) noncommutative and nonassociative algebras $\bbO_{p,q}$ (resp. $\bbO_{n}$) generalizing the algebra of octonion numbers $\bbO$. This generalization is similar to the one of the algebra of quaternion numbers in Clifford algebras. Introduced by Morier-Genoud and Ovsienko, these algebras have a natural $\bbZ_2^n$-grading ($p+q =n$), and they are characterized by a cubic form over the field $\bbZ_2.$ We establish all the possible isomorphisms between the algebras $\bbO_{p,q}$ preserving the structure of $\bbZ_2^n$-graded algebra. The classification table of $\bbO_{p,q}$ is quite similar to that of the real Clifford algebras $\cC l_{p,q}$, the main difference is that the algebras $\bbO_{n,0}$ and $\bbO_{0,n}$ are exceptional. We also provide a periodicity for the algebras $\bbO_n$ and $\bbO_{p,q}$ analogous to the periodicity for the Clifford algebras $\cC l_{n}$ and $\cC l_{p,q}$. In the second part we consider superalgebras of Krichever-Novikov (K-N) type. Krichever and Novikov introduced a family of Lie algebras with two marked points generalizing the Witt algebra and its central extension called the Virasoro algebra. The K-N Lie (super)algebras for more than two marked points were studied by Schlichenmaier. In particular, he extended the explicit formula of $2$-cocycles due to Krichever and Novikov to multiple-point situation. We give an explicit construction of central extensions of Lie superalgebras of K-N type and we establish a $1$-cocycle with values in its dual space. In the case of Jordan superalgebras related to superalgebras of K-N type, we calculate a 1-cocycle with coefficients in the dual space. [less ▲]

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See detailFictions du groupe littéraire
Saint-Amand, Denis ULg

Scientific conference (2015, April 17)

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See detailImpact of Aphasia on Consciousness Assessment: A Cross-Sectional Study.
Schnakers, C; Bessou, H; Rubi-Fessen, I et al

in Neurorehabilitation & Neural Repair (2015), 29

BACKGROUND: . Previous findings suggest that language disorders may occur in severely brain-injured patients and could interfere with behavioral assessments of consciousness. However, no study ... [more ▼]

BACKGROUND: . Previous findings suggest that language disorders may occur in severely brain-injured patients and could interfere with behavioral assessments of consciousness. However, no study investigated to what extent language impairment could affect patients' behavioral responses. OBJECTIVE: . To estimate the impact of receptive and/or productive language impairments on consciousness assessment. METHODS: . Twenty-four acute and subacute stroke patients with different types of aphasia (global, n = 11; Broca, n = 4; Wernicke, n = 3; anomic, n = 4; mixed, n = 2) were recruited in neurology and neurosurgery units as well as in rehabilitation centers. The Coma Recovery Scale-Revised (CRS-R) was administered. RESULTS: . We observed that 25% (6 out of 24) of stroke patients with a diagnosis of aphasia and 54% (6 out of 11) of patients with a diagnosis of global aphasia did not reach the maximal CRS-R total score of 23. An underestimation of the consciousness level was observed in 3 patients with global aphasia who could have been misdiagnosed as being in a minimally conscious state, even in the absence of any documented period of coma. More precisely, lower subscores were observed on the communication, motor, oromotor, and arousal subscales. CONCLUSION: . Consciousness assessment may be complicated by the co-occurrence of severe language deficits. This stresses the importance of developing new tools or identifying items in existing scales, which may allow the detection of language impairment in severely brain-injured patients. [less ▲]

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