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See detailNonlinear ground vibration identification of an F-16 aircraft - Part 1: Fast nonparametric analysis of distortions in FRF measurements
Vaes, Mark; Schoukens, Johan; Peeters, Bart et al

in Proceedings of the International Forum on Aeroelasticity and Structural Dynamics (2015, June)

Although they are generally modelled as linear systems, aircraft structures are known to be prone to nonlinear phenomena. A specific challenge encountered with fighter aircraft, besides aeroelastic ... [more ▼]

Although they are generally modelled as linear systems, aircraft structures are known to be prone to nonlinear phenomena. A specific challenge encountered with fighter aircraft, besides aeroelastic nonlinearity, is the modelling of the wing-to-payload mounting interfaces. For large amplitudes of vibration, friction and gaps may be triggered in these connections and markedly impact the dynamic behaviour of the complete structure. In this series of two papers, the nonlinear dynamics of an F-16 aircraft is investigated using rigorous methods applied to real data collected during a ground vibration test campaign. The present work focuses on the detection, qualification and quantification of nonlinear distortions affecting frequency response function (FRF) measurements. The key idea of the approach is to excite the structure using a random signal with a user-defined amplitude spectrum, where only a set of well-selected frequencies is different from zero in the band of interest. It is demonstrated that this careful choice of the input frequencies allows, without any further user interaction, to quantify the importance of odd and even nonlinear distortions in the output spectra with respect to the noise level. At high excitation amplitude, the F-16 dynamics is found to exhibit substantial odd nonlinearities and less significant, yet not negligible, even nonlinearities. [less ▲]

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See detailNonlinear model updating by means of identified nonlinear normal modes
Song, Mingming; Renson, Ludovic ULg; Noël, Jean-Philippe ULg et al

Conference (2015, June)

Modal parameters are the most common features used for linear model updating. Although the modal analysis theory does not hold for nonlinear dynamic systems, its popularity encouraged researchers to come ... [more ▼]

Modal parameters are the most common features used for linear model updating. Although the modal analysis theory does not hold for nonlinear dynamic systems, its popularity encouraged researchers to come up with an equivalent version of normal modes for nonlinear systems, i.e., nonlinear normal modes (NNMs). A nonlinear system vibrates in NNMs when all masses have periodic motions of the same period, and at any time, the position of all the masses is uniquely defined by the position of any one of them. This paper investigates the feasibility of nonlinear model updating by minimizing the difference between the model-predicted and measured/identified nonlinear normal modes. A two degree-of-freedom mass-spring system with three linear springs and a cubic nonlinear spring is considered as the case study. The energy-dependent natural frequency and NNM of the first vibration mode of the system are identified at three different levels of energy. The stiffness parameters of the system are estimated by minimizing an objective function which is defined as the discrepancy between model-predicted natural frequency and NNM of the first mode, and their identified counterparts at the three measured energy levels. Performance of the proposed updating approach is evaluated at different levels of noise and different levels of modeling errors (i.e., nonlinear model classes). [less ▲]

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See detailTime and aspect: what the academic grammars say, and what the texts actually show
Winand, Jean ULg

Scientific conference (2015, May 29)

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See detailFragmentation urbaine à travers les réseaux techniques
Cabrera Quispe, Juan Edson ULg

Doctoral thesis (2015)

Since about three decades ago, the networking services (water, energy, transport and telecommunications) are the subject of studies and mainly reforms (liberalization, privatization and concessions to ... [more ▼]

Since about three decades ago, the networking services (water, energy, transport and telecommunications) are the subject of studies and mainly reforms (liberalization, privatization and concessions to private companies, etc.) and also an important economic policy issue. However the possible effects of these reforms on the fragmentation or integration of urban societies are still poorly studied, although some studies (mainly on developing cities) support the thesis that there would be a growing urban fragmentation, reinforced by the dominant modes of implementing reforms network services. One of the most important theses about the subject is in a relatively recent development of the English authors Stephen Graham and Simon Marvin (2001). Their work generalizes the motion of fragmentation (splintering Urbanism) to all network services and a set of economic regions in the world. While this thesis presents consistency and validity - since it is known that the application of models of decentralization and liberalization of services has an effect on the fragmentation - the position of fragmentation due to centralized networks is inside a new analysis framework and still incomplete considering the absence of more empirical evidence. The thesis of fragmentation from centralized networks suggests that powerful factors are contributing to the disintegration of infrastructure, favoring the fragmentation of the social structure and material of cities. In fact, this breakdown of infrastructures makes possible many strategies of evasion; they are addressed to connect powerful users and valorized spaces, preventing the connection with less powerful users and poor spaces. These processes lead to the creation of spaces from different social networks, resulting in social elites living every day in places disconnected from the urban structure of the set (in gated communities, new complex people and other planned communities), as well as the lower classes, but the latter with the worst conditions. The main hypothesis of the "splintering Urbanism" argues that network services have an integrated character and are precisely the privatization and liberalization of services that contribute to the breakdown of network infrastructure and urban fragmentation feed. The control of networks from powerful coalitions of actors, separation and segmentation boost infrastructure in different network elements and service pack (2001: 141). This separation would occur across strategies "bypass" or "wrap" seeking to connect users, valuable or powerful places, and through discarding or dodge weaker users and worthless places. Our thesis "Urban Fragmentation through technical networks," confirms and reinforces the thesis made by Graham & Marvin, across expounding on the Cochabamba Bolivian context, a set of technical networks of small-scale or micro decentralized networks which are managed by autonomous social organizations that also fragment the territory without the need for "by pass" and the socio-spatial differentiation, but through the realization of strategies linked to autonomous administration and management of common and basic goods like water. This thesis demonstrates the existence of processes of spatial dislocation and loss of solidarity (main evils of urban fragmentation) across the dynamics of technical devices and decentralized networks infrastructure services from private-community water and small scale. However, our work describes in its urban development, territorial and environmental problems inside the phenomenon. The paper first presents a set of theories that attempt to explain the fragmentation and its particularities, then describes the socio-spatial formation of the study area whose characteristics allow this type of phenomenon, to arrive to a section that exposes all the particularities of the management water from public and local actors, analyzed from the environmental logic of urban water cycle, including the specifics of the main stage of study of this thesis, the municipality of Quillacollo in Cochabamba. From a spatial perspective, the thesis exhibits the characteristics of urban fragmentation across technical networks, exposing the details related to the organization of urban space as a result of processes of spatial dislocation, loss of solidarity and exercise of territoriality in small networks. It is concluded in a discussion about the validity of the strategies in terms of access to the resource, the possibilities of intervention and reflections about the power relationships among fragments and for water control. Finally, as a supplement, urban fragmentation through small technical networks, also allows to display the tensions between two ways of managing the territory (centralized view from the public sector and decentralized vision from local communities) highlighting the uncomfortable and marginalized urban planning position, but challenging the urbanism to recover to action on the highly fragmented contemporary cities with complex scenarios of governance and sometimes rare or endangered resources. [less ▲]

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See detailLe donné phénoménal de Tim Crane
Gauvry, Charlotte ULg

Conference (2015, May 28)

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See detailPsychopathy and emotions: would emotional distancing make more efficient in cognitive tasks?
Grandjean, Sylvie; Dehon, Hedwige ULg; Blavier, Adelaïde ULg et al

Poster (2015, May 28)

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See detailBorderline Personality Disorder through the Rorschach test
Rommes, Jennifer; Englebert, Jérôme ULg; Blavier, Adelaïde ULg

Poster (2015, May 28)

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See detailWork incapacity and chronic pain patients: Is there an impact of work incapacity on anxiety and depression?
Beaumel, Alexia; Vanootighem, Valentine ULg; Gillet, Aline ULg et al

Poster (2015, May 28)

In 2011, a report of the Federal Public Service have shown that 8.5% of the Belgian population suffers from chronic pains, which represents 938 300 belgian people (Berquin et al., 2011). These persistent ... [more ▼]

In 2011, a report of the Federal Public Service have shown that 8.5% of the Belgian population suffers from chronic pains, which represents 938 300 belgian people (Berquin et al., 2011). These persistent pains may result in functional limitations on both domestic and professional domains which may lead to temporary or permanently work incapacity (Faymonville et al., 2014). These incapacities may in turn cause a social withdrawal and a tendency to focus on pain (Berquin et al., 2011). Additionally, patients are prone to emotional modifications due to persistent pain (Ossipov et al., 2010). All of these factors may contribute in the emergence of anxiety and depressive symptoms. The present study examines the impact of type of work incapacities (at work, temporary incapacity and permanent incapacity) on anxiety and depression scores as a function of diagnoses (fibromyalgia, chronic pain syndrome, back pain, polyalgia). 123 patients suffering from chronic pain completed a measure of anxiety and depression (HADS), and a self-reported questionnaire of psychological and physical disability at work. We did not found any significant effect of type of work incapacities on anxiety and depression scores. Results present tables of frequencies to illustrate the social and professional situations of patients as a function of chronic pain diagnoses. [less ▲]

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See detailMake the ureter your friend
Bonnet, Pierre ULg

Conference (2015, May 22)

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See detailQuels profils caractérisés par l'humeur, l'activation comportementale et les stratégies de régulation émotionnelle pouvons-nous identifier dans une population adulte ?
Wagener, Aurélie ULg

Conference (2015, May 22)

The behavioural model of depression put forward that the level of activities in depressed patients decreases which maintains their low mood. Depressed patients are also known to use non-adaptive cognitive ... [more ▼]

The behavioural model of depression put forward that the level of activities in depressed patients decreases which maintains their low mood. Depressed patients are also known to use non-adaptive cognitive coping strategies (e.g. rumination, catastrophizing). Previous research underlined that cognitive coping strategies predict the level of activation (non-adaptive cognitive coping strategies predict a low level of activation). According to the dimensional approach of psychopathology, we hypothesised that sub-groups of depressed and non-depressed adults could be identified depending on their level of activation and the kind of cognitive coping strategies they use. In order to test this hypothesis, we investigated the relationships between the level of activation, the cognitive coping strategies, anxiety and depression with a cluster-analysis approach. 762 adults (530 women, 232 men; mean age= 31.54, SD= 12.08) completed an online survey assessing the above-mentioned variables with self-reports measures (BADS-SF, CERQ, BDI-II, STAI-Y B). Results identified four clusters that differed according to the level of activation, the cognitive coping strategies, the anxiety and the depression. For instance, one of the four classes highlighted that non-active depressed adults used catastrophizing and rumination contrary to another classes of active non-depressed ones. These results, providing interesting guidelines for psychological interventions, will be discussed further during the congress. [less ▲]

Peer Reviewed
See detailAssessing employees propensity to engage in OCB: incremental validity of SJT beyond personality.
Lothe, Benoit ULg; Hansez, Isabelle ULg; Scius, Anthony et al

Conference (2015, May 21)

This study presents the validation results of a SJT developed in collaboration with a Belgian french speaking mutual insurance company for the assessment of employees OCB. The purpose is to provide ... [more ▼]

This study presents the validation results of a SJT developed in collaboration with a Belgian french speaking mutual insurance company for the assessment of employees OCB. The purpose is to provide empirical evidence concerning the validity of using the SJT by examining the issues of OCB criterion validity, incremental validity beyond a personality inventory, applicant perception and SJT transparency level. The SJT was developed in-house and following relevant literature recommendations (Weekley, Ployhart & Holtz, 2006). Data were collected on 117 white-collar employees. Three other measurements were concurrently collected: OCB using Williams & Anderson (1991) self-reported scales, personality using the Gosling, Rentfrow & Swann (2003) ten item inventory (TIPI) and applicant perception using SPJS (Bauer, & al., 2001). An open-ended question was used to access the extent to which applicants are able to identify the SJT criteria. Results indicated that the SJT is a relevant predictor of OCB (r = .42; p<.001). The SJT also provides incremental explanation of the OCB criteria beyond the personality inventory (∆R² = .11; p<.001). There was in average an agreement about the acceptability of the SJT in terms of perceived procedural justice. No relationships were found between applicant ability to correctly identify the SJT criteria and SJT score or OCB self-rating. This study is to our knowledge among the first attempt to develop and validate a tool to fill the gap on how to predict employees OCB (Organ, Podsakoff & Podsakoff, 2010). Implications for the personnel selection and current limitations will be discussed. [less ▲]

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See detailL'enfant parentifié: un enfant en souffrance
Haxhe, Stéphanie ULg

Conference given outside the academic context (2015)

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See detailHow shattered flakes were used : Micro-wear analysis of quartz flake fragments
Knutsson, Helena; Knutsson, Kjel; Taipale, Noora ULg et al

in Journal of Archaeological Science: Reports (2015), 2

Prehistoric quartz assemblages have always posed a special problem for archaeologists. Due to its brittle nature, quartz is hard to understand within lithic classification systems that are based on ... [more ▼]

Prehistoric quartz assemblages have always posed a special problem for archaeologists. Due to its brittle nature, quartz is hard to understand within lithic classification systems that are based on formally varied flint assemblages. In this paper we explore ways to deal with this problem by applying two analytical methods, fracture analysis and use-wear analysis. A sample of 544 unmodified quartz flakes and flake fragments from Mesolithic and Neolithic sites in Sweden and Finland was analysed. It can be concluded that both whole and fragmented flakes were used as tools. Larger flakes and flake fragments were preferred as tool blanks and the type of use was correlated to variation in edge qualities rather than the formal characteristics of flakes. The results of this investigation suggest that making behavioural inferences from quartz assemblages with low formal variability requires the assemblages to be approached with a focus on functional types. [less ▲]

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See detailAcetylene (C2H2) and hydrogen cyanide (HCN) from IASI satellite observations: global distributions, validation, and comparison with model
Duflot, V.; Wespes, C.; Clarisse, L. et al

in Atmospheric Chemistry & Physics Discussions (2015), 15(10), 14357--14401

We present global distributions of C2H2 and HCN total columns derived from the Infrared Atmospheric Sounding Interferometer (IASI). These distributions are obtained with a fast method allowing to retrieve ... [more ▼]

We present global distributions of C2H2 and HCN total columns derived from the Infrared Atmospheric Sounding Interferometer (IASI). These distributions are obtained with a fast method allowing to retrieve C2H2 abundance globally with a 5% precision and HCN abundance in the tropical (subtropical) belt with a 10% (30%) precision. IASI data are compared for validation purposes with ground-based Fourier Transform Infrared (FTIR) spectrometer measurements at four selected stations. We show that there is an overall agreement between the ground-based and space measurements. Global C2H2 and subtropical HCN abundances retrieved from IASI spectra show the expected seasonality linked to variations in the anthropogenic emissions and seasonal biomass burning activity, as well as exceptional events, and are in good agreement with previous spaceborne studies. IASI measurements are also compared to the distributions from the Model for Ozone and Related Chemical Tracers, version 4 (MOZART- 4). Seasonal cycles observed from satellite data are reasonably well reproduced by the model. However, the model seems to overestimate (underestimate) anthropogenic (biomass burning) emissions and a negative global mean bias of 1% (16 %) of the model relative to the satellite observations was found for C2H2 (HCN). [less ▲]

Detailed reference viewed: 9 (0 ULg)