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See detailDoes physical learning environment matter? Effects after the move to a new campus on the perception of the quality of studies
Steffgen, Georges UL; Vesely, Jana; Pinto Costa, Andreia UL

Poster (2017, September 18)

The present study examined the effects of a move to a new physical learning environment – Belval Campus – on the students’ satisfaction with the course program in psychology. It was hypothesized that the ... [more ▼]

The present study examined the effects of a move to a new physical learning environment – Belval Campus – on the students’ satisfaction with the course program in psychology. It was hypothesized that the move to a new and modern University campus with better study facilities increases course climate, learning promotion, and skill acquisition. Participants were 538 undergraduate students who completed the Bachelor Evaluation Questionnaire, which assessed the perceived quality of the course program as well as five infrastructure and equipment aspects of the new campus. Findings show that students were more satisfied with the classrooms, the capacity of the rooms, and the library facilities, but there was no increase in perceived course climate, learning promotion, and skill acquisition of the students after 6 months nor after 18 months from the move. The implications of these findings for the need to change physical learning environments are discussed and recommendations for the design of learning environments are presented. [less ▲]

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See detailAvatar Sex Moderates Aggression in Violent Video Games, But Only for Women
Melzer, André UL; Schmidt, Alexander F.

Poster (2017, September 07)

Three studies tested findings reported by Yang, Huesmann, and Bushman (2014) that playing a male avatar in a violent video game leads to greater aggression than playing a female avatar in the same game ... [more ▼]

Three studies tested findings reported by Yang, Huesmann, and Bushman (2014) that playing a male avatar in a violent video game leads to greater aggression than playing a female avatar in the same game. The male avatar effect was confirmed in Study 1 (N=79) for post-game aggression: compared to playing a female character, participants who had played the male fighter in a violent mixed martials arts game chose more Hot Sauce for another participant who allegedly disliked spicy food. In contrast to Yang et al. (2014), however, the male avatar effect was qualified by participant sex, indicating that the effect was more strongly pronounced and only significant for female participants. A similar interaction effect was observed in Study 2 (N=76) and Study 3 (N=70) for in-game aggression: only female participants playing a male avatar showed a greater hit ratio in a mixed martials arts game (Study 2) or a greater number of attacks in a brawler game (Study 3) than their colleagues who played a female avatar. At this stage, the reason for this cross-gender effect is unclear. Given that games allow for behavior (i.e., aggression) independent of socially shared gender norms, we may speculate that for women, male avatars may provide the opportunity to “step out” of prevailing social norms regarding non-aggressive female behavior and adopt the role of the (hyper-)aggressive male. However, this hypothesis needs to be tested in future studies. All three studies additionally tested the mediating effect of male gender stereotype activation that was hypothesized by Yang et al. (2014). In addition to priming violent behavior, and in line with the General Aggression Model, the authors had speculated that playing the male avatar automatically activated male gender stereotypes (i.e., aggressive thoughts and behavior) which then caused aggressive behavior. In order to address this activation hypothesis, we designed an indirect cognitive measure of gender role identity using the Positive-Negative Sex-Role Inventory (PN-SRI: Berger & Krahé, 2013). After participants played the violent game, positive and negative aspects of masculinity and femininity were presented as word fragments in a five-minute response window in Study 1 and 2. Fragment completion rates served as indicators of cognitive activation of male stereotypes. In Study 3, participants used the intact PN-SRI gender attributes to rate the avatar after playing the game. However, both direct and indirect measures failed to corroborate the stereotype activation hypothesis in the present studies: word fragments related to male stereotypes were not completed more often than fragments related to female stereotypes (Study 1 and 2). Also, neither in-game aggression nor success in the game was associated with how masculine participants perceived their fighter (Study 3). At the present stage, thus, the mechanisms underlying the gender effect that participants respond differently when playing a male or female avatar in a violent video game remain unclear. [less ▲]

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See detailThe relevance of verbal and visuo-spatial abilities for verbal number skills – what matters in 5 to 6 year olds?
Cornu, Véronique UL; Schiltz, Christine UL; Martin, Romain UL et al

Poster (2017, September)

The acquisition of verbal number skills, as defined by the meaningful use of number words, marks a milestone in numerical development. In the present study, we were particularly interested in the question ... [more ▼]

The acquisition of verbal number skills, as defined by the meaningful use of number words, marks a milestone in numerical development. In the present study, we were particularly interested in the question, whether verbal number skills are primarily verbal in nature, or if they call upon visuo-spatial processes, reflecting a spatial grounding of verbal number skills. 141 five- to six-year old children were tested on a range of verbal (i.e. vocabulary, phonological awareness and verbal working memory) and visuo-spatial abilities (i.e. spatial perception, visuo-motor integration and visuo-spatial working memory). We were particularly interested in the predictive role of these abilities for children’s verbal number skills (as measured by different counting and number naming tasks). In a latent regression model, basic visuo-spatial abilities, measured by spatial perception and visuo-motor integration, emerge as the most important predictor of verbal number skills. This gives raise to the assumption, that verbal number skills are, despite their verbal nature, spatially grounded in young children. [less ▲]

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See detailImpact of the Time of Diagnosis on Dyslexic Adolescents' Self-efficacy beliefs
Battistutta, Layla UL; Commissaire, Eva; Steffgen, Georges UL

Poster (2017, September)

Aim: Most of the research on self-efficacy in children with specific learning disorders has focused on inter-group comparisons, showing that these children hold lower self-efficacy scores than their ... [more ▼]

Aim: Most of the research on self-efficacy in children with specific learning disorders has focused on inter-group comparisons, showing that these children hold lower self-efficacy scores than their normally developing peers. As these lower scores might be due to a reduced access to self-efficacy sources (Hampton & Mason, 2003), this small-scale study (N=18) aimed to investigate whether the time of diagnosis might modulate the access to these sources within a group of dyslexic adolescents, either diagnosed in primary or secondary school but paired on chronological age and duration of remedial training. Methods: Mixed methods were employed by using general as well as academic and social self-efficacy scales, complemented by semi-structured interviews investigating students’ understanding and acceptance of their dyslexia. Results: The findings showed that early-diagnosed students hold higher general and academic scores. Further analyses regarding students’ personal statements revealed a statistically significant association between time of diagnosis and understanding as well as tolerance of dyslexia, indicating that early-diagnosed adolescents, compared to their late-diagnosed peers, have a more cohesive understanding and more adequate representations of their reading disorder as specific and non-stigmatizing, all the while being more tolerant and open about announcing their dyslexia to others. Conclusions: An early diagnosis of dyslexia is thus associated with a better understanding and acceptance of the disorder, possibly serving as a protective factor which can consequently contribute to higher general and academic self-efficacy scores. Hence, these findings not only extend the literature on self-efficacy beliefs in dyslexia by investigating the time of diagnosis, but also have important practical implications, highlighting the significance of an early diagnosis beyond the benefits of early rehabilitation as well as the potentially negative psychological consequences of a late diagnosis. [less ▲]

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See detailA Global Vertical Land Movement Data Set from a Combination of Global Navigation Satellite System Solutions
Hunegnaw, Addisu UL; Teferle, Felix Norman UL; Abraha, Kibrom Ebuy UL et al

Poster (2017, July 13)

Coastal sea-level measurements by tide gauges provide the longest instrumental records of sea-levels with some stretching from the 19th century to present. The derived mean sea-level (MSL) records provide ... [more ▼]

Coastal sea-level measurements by tide gauges provide the longest instrumental records of sea-levels with some stretching from the 19th century to present. The derived mean sea-level (MSL) records provide sea-level relative to a nearby tide gauge benchmark (TGBM), which allows for the continuation of this record in time after, for example, equipment modifications. Any changes in the benchmark levels induced by vertical land movements (VLM) affect the MSL records and hence the computed sea-levels. In the past, MSL records affected by VLM were often excluded from further analyses or the VLM were modelled using numerical models of the glacial isostatic adjustment (GIA) process. Over the last two decades Global Navigation Satellite System (GNSS), in particular Global Positioning System (GPS), measurements at or close to tide gauges and the development of the associated processing strategies, have made it possible to obtain estimates of VLM in a geocentric reference system, such as the International Terrestrial Reference Frame release 2008 (ITRF2008) that approach the required accuracy for sea-level studies. Furthermore, the GPS-derived VLM estimates have been shown to improve estimates of sea-level change compared to those using the aforementioned GIA models as these models cannot predict local subsidence or uplift. The International GNSS Service (IGS) Tide Gauge Benchmark Monitoring (TIGA) Working Group has recently re-processed the global GNSS data set from its archive (1000+ stations for 1995-2014) to provide VLM estimates tuned for the sea-level community. To achieve this, five TIGA Analysis Centers (TAC) contributed their reprocessed global GPS network solutions to the WG, all employing the latest bias models and processing strategies in accordance with the second re-processing compaign (repro2) of the IGS. These individual solutions were then combined by the TIGA Combination Center (TCC) to produce, for the first time, a TIGA combined solution (Release 0.99). This combined solution allows an evaluation of each individual TAC solution while also providing a means to gauge the quality and reliability of the combined solution, which is generally regarded as superior to the individual TAC solutions. Using time series analysis methods, estimates of VLM can then be derived from the daily position estimates, which are sub-sequentially employed to investigate coastal sea-levels. In this study, we show results from the evaluation of the relevant solutions, provide an evaluation of the TIGA VLM estimates and give examples of their impact on sea-level estimates for selected tide gauges from around the world. The TAC and TIGA combined solutions, as well as the derived VLM data sets are available from the IGS TIGA WG and will be accessible through SONEL (www.sonel.org) in the near future. [less ▲]

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See detailPoster: Impact of ground truth errors on Wi-Fi localization accuracy
Popleteev, Andrei UL

Poster (2017, June)

This study investigates the impact of small ground truth (GT) errors on indoor positioning systems based on Wi-Fi fingerprinting. The results demonstrate that even centimeter-scale GT deviations cause ... [more ▼]

This study investigates the impact of small ground truth (GT) errors on indoor positioning systems based on Wi-Fi fingerprinting. The results demonstrate that even centimeter-scale GT deviations cause severe degradation of measured localization accuracy. [less ▲]

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See detailParentalité en situation vulnérable: trajectoires de résilience familiale?
Dujardin, Céline UL

Poster (2017, May 19)

Le domaine de la protection de la jeunesse porte sur la prise en charge de situations familiales de vulnérabilité qui peuvent engendrer des impacts négatifs sur le développement de l'enfant. A l'inverse ... [more ▼]

Le domaine de la protection de la jeunesse porte sur la prise en charge de situations familiales de vulnérabilité qui peuvent engendrer des impacts négatifs sur le développement de l'enfant. A l'inverse, la notion de résilience permet la perspective sur une trajectoire familiale qui compense le danger pour le développement de l'enfant et le fonctionnement familial. La thèse est développée dans le but d'offrir un cadre de réflexion aux réponses élaborées aussi bien par les services d'aides que par les familles elles-mêmes face aux difficultés rencontrées, tenant compte des particularités liées au contexte luxembourgeois. [less ▲]

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See detailA PetriNet Mechanism for OLAP in NUMA
Dominico, Simone; Almeida, Eduardo Cunha de; Meira, Jorge Augusto UL

Poster (2017, May 15)

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See detailLuxemburg und der Studiengang der Sozialen Arbeit
Böwen, Petra UL; Dujardin, Céline UL; Straus, Liz UL

Poster (2017, May 10)

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See detailUnderstanding Android App Piggybacking
Li, Li UL; Li, Daoyuan UL; Bissyande, Tegawendé François D Assise UL et al

Poster (2017, May)

The Android packaging model offers adequate opportunities for attackers to inject malicious code into popular benign apps, attempting to develop new malicious apps that can then be easily spread to a ... [more ▼]

The Android packaging model offers adequate opportunities for attackers to inject malicious code into popular benign apps, attempting to develop new malicious apps that can then be easily spread to a large user base. Despite the fact that the literature has already presented a number of tools to detect piggybacked apps, there is still lacking a comprehensive investigation on the piggybacking processes. To fill this gap, in this work, we collect a large set of benign/piggybacked app pairs that can be taken as benchmark apps for further investigation. We manually look into these benchmark pairs for understanding the characteristics of piggybacking apps and eventually we report 20 interesting findings. We expect these findings to initiate new research directions such as practical and scalable piggybacked app detection, explainable malware detection, and malicious code location. [less ▲]

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See detailThe Multi-Generation Repackaging Hypothesis
Li, Li UL; Bissyande, Tegawendé François D Assise UL; Bartel, Alexandre UL et al

Poster (2017, May)

App repackaging is a common threat in the Android ecosystem. To face this threat, the literature now includes a large body of work proposing approaches for identifying repackaged apps. Unfortunately ... [more ▼]

App repackaging is a common threat in the Android ecosystem. To face this threat, the literature now includes a large body of work proposing approaches for identifying repackaged apps. Unfortunately, although most research involves pairwise similarity comparison to distinguish repackaged apps from their “original” counterparts, no work has considered the threat to validity of not being able to discover the true original apps. We provide in this paper preliminary insights of an investigation into the Multi-Generation Repackaging Hypothesis: is the original in a repackaging process the outcome of a previous repackaging process? Leveraging the Androzoo dataset of over 5 million Android apps, we validate this hypothesis in the wild, calling upon the community to take this threat into account in new solutions for repackaged app detection. [less ▲]

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See detailEvaluation of ERA-Interim for tropospheric delay and water vapour estimation in different climate zones using ground-based GNSS observations
Ahmed, Furqan; Hunegnaw, Addisu UL; Teferle, Felix Norman UL et al

Poster (2017, April 27)

Tropospheric delay and integrated water vapour (IWV) derived from climate reanalysis models, such as that of the European Centre for Medium-range Weather Forecasts (ECMWF) namely the ECMWF ReAnalysis ... [more ▼]

Tropospheric delay and integrated water vapour (IWV) derived from climate reanalysis models, such as that of the European Centre for Medium-range Weather Forecasts (ECMWF) namely the ECMWF ReAnalysis-Interim (ERA-Interim), are widely used in many geodetic and atmospheric applications. Therefore, it is of interest to assess the quality of these reanalysis products using available observations. Observations from Global Navigation Satellite Systems (GNSS) are, as of now, available for a period of over 2 decades and their global availability make it possible to validate the zenith total delay (ZTD) and IWV obtained from climate reanalysis models in different geographical and climatic regions. In this study, a 5-year long homogeneously reprocessed GNSS data set based on double differenced positioning strategy and containing over 400 globally distributed ground-based GNSS stations has been used as a reference to validate the ZTD estimates obtained from the ERA-Interim climate reanalysis model in 25 different climate zones. It has been studied how the difference between the ERA-Interim ZTD and the GNSS-derived ZTD varies with respect to the different climate zones as well as the topographic variations in a particular climate zone. Periodicity in the ZTD residuals in different climate zones has been analyzed. Furthermore, the variation of the ZTD differences with respect to latitude has been presented. Finally, for one GNSS station in each of the 25 climate zones, IWV derived from ERA-Interim has been compared to the IWV derived using GNSS observations. [less ▲]

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See detailA New Global Vertical Land Movement Data Set from the TIGA Combined
Hunegnaw, Addisu UL; Teferle, Felix Norman UL; Abraha, Kibrom Ebuy UL

Poster (2017, April 23)

Globally averaged sea level has been estimated from the network of tide gauges installed around the world since the 19th century. These mean sea level (MSL) records provide sea level relative to a nearby ... [more ▼]

Globally averaged sea level has been estimated from the network of tide gauges installed around the world since the 19th century. These mean sea level (MSL) records provide sea level relative to a nearby tide gauge benchmark (TGBM), which allows for the continuation of the instrumental record in time. Any changes in the benchmark levels, induced by vertical land movements (VLM) affect the MSL records and hence sea level estimates. Over the last two decades sea level has also been observed using satellite altimeters. While the satellite observations are globally more homogeneous providing a picture of sea level not confined to coastlines, they require the VLM-corrected MSL records for the bias calibration of instrumental drifts. Without this calibration altimeter instruments from different missions cannot be combined. GPS has made it possible to obtain highly accurate estimates of VLM in a geocentric reference frame for stations at or close to tide gauges. Under the umbrella of the International GNSS Service (IGS), the Tide Gauge Benchmark Monitoring (TIGA) Working Group (WG) has been established to apply the expertise of the GNSS community to solving issues related to the accuracy and reliability of the vertical component to provide estimates of VLM in a well-defined global reference frame. To achieve this objective, five TIGA Analysis Centers (TACs) contributed re-processed global GPS network solutions to TIGA, employing the latest bias models and processing strategies in accordance with the second re-processing campaign (repro2) of the IGS. These solutions include those of the British Isles continuous GNSS Facility – University of Luxembourg consortium (BLT), the German Research Centre for Geosciences (GFZ) Potsdam, the German Geodetic Research Institute (DGF) at the Technical University of Munich, Geoscience Australia (AUT) and the University of La Rochelle (ULR). In this study we present to the sea level community an evaluation of the VLM estimates from the first combined solution from the IGS TIGA WG. The TAC solutions include more than 700 stations and span the common period 1995-2014. The combined solution was computed by the TIGA Combination Centre (TCC) at the University of Luxembourg, which used the Combination and Analysis of Terrestrial Reference Frame (CATREF) software package for this purpose. This first solution forms Release 1.0 and further releases will be made available after further reprocessing campaigns. We evaluate the combined solution internally using the TAC solutions and externally using solutions from the IGS and the ITRF2008. The derived VLM estimates have undergone an initial evaluation and should be considered as the primary TIGA product for the sea level community to correct MSL records for land level changes [less ▲]

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See detailMechanical characterisation of alkali activated clay - based geopolymer binder made out of gravel wash mud
Thapa, Vishojit Bahadur UL; Waldmann, Danièle UL; Wagner, Jean-Frank et al

Poster (2017, April 03)

One of the most promising cement alternatives are geopolymer cements. The term “geopolymer” was mentioned for the first time by Davidovits and classifies all forms of inorganic polymeric material ... [more ▼]

One of the most promising cement alternatives are geopolymer cements. The term “geopolymer” was mentioned for the first time by Davidovits and classifies all forms of inorganic polymeric material synthesised by chemical reaction of aluminosilicates and an alkaline activating solution. The production of geopolymer binder comprises in two main procedures: calcination and geopolymerisation. The synthesised geopolymer shows interesting characteristics like good mechanical properties, high strength and good durability. [less ▲]

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See detailTesting measurement Invariance in a CFA framework – State of the art
Sischka, Philipp UL

Poster (2017, March 31)

In recent years, several studies have stressed out the importance to guarantee the comparability of theoretical constructs (i.e. measurement invariance) in the compared units (e.g., groups or time points ... [more ▼]

In recent years, several studies have stressed out the importance to guarantee the comparability of theoretical constructs (i.e. measurement invariance) in the compared units (e.g., groups or time points) in order to conduct comparative analyses (e.g. Harkness, Van de Vijver, & Mohler, 2003; Meredith, 1993; Vandenberg, & Lance, 2000). If one does not test for measurement invariance (MI) or ignores lack of invariance, differences between groups in the latent constructs cannot be unambiguously attributed to ‘real’ differences or to differences in the measurement attributes. One approach to test for MI is in a confirmatory factor analysis (CFA) framework. In this framework, MI is usually tested with a series of model comparisons that define more and more stringent equality constraints. The presentation will be about new developments in the MI-CFA framework. Among other things, the presentation tries to answer the following questions: • Which scale setting method to use (marker variable, fixed factor or effect coding method) when testing for MI? • Should a top-down- or bottom-up-approach be used? • How to test MI with a large number of groups (>30)? • What are the possibilities to evaluate whether MI exists (e.g., statistical significance of the ∆² after Bonferroni adjustment, changes in approximate fit statistics, magnitude of difference between the parameter estimates)? • How to determine confidence intervals for fit indices? • Can MI be graphically analyzed? • How can be dealt with non-invariance? These questions will be tried to answered by an application to a real world dataset (N ~ 40.000), with a one-factor/five indicator model of a well-being scale tested in 35 groups. [less ▲]

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See detailThe influence of Forced Answering on response behavior in Online Surveys: A reactance effect?
Sischka, Philipp UL; Mergener, Alexandra; Neufang, Kristina Marliese et al

Poster (2017, March 16)

Relevance: Recent studies have shown that the use of the forced answering (FA) option in online surveys results in reduced data. They especially examined that forcing respondents to answer questions in ... [more ▼]

Relevance: Recent studies have shown that the use of the forced answering (FA) option in online surveys results in reduced data. They especially examined that forcing respondents to answer questions in order to proceed through the questionnaire leads to higher dropout rates and lower answer quality. However, no study researched the psychological mechanism behind the correlation of FA on dropout and data quality before. This response behavior has often been interpreted as psychological reactance reaction. So, the Psychological Reactance Theory (PRT) predicts that reactance appears when an individuals’ freedom is threatened and cannot be directly restored. Reactance describes the motivation to restore this loss of freedom. Respondents could experience FA as a loss of freedom, as (s)he is denied the choice to leave a question unanswered. According to PRT, possible reactions in this situation might be to quit survey participation, to fake answers or to show satisficing tendencies. Research content: This study explores the psychological mechanism that effects response behavior in FA condition (compared to non-FA- condition). Our major hypothesis is that forcing respondents to answer will cause reactance, which turns into increasing dropout rates, decreasing answer quality and a satisficing behavior. Methods and Data: We used an online survey-experiment with two conditions (forced and non-forced answering instructions). The sample consists of 914 participants. Throughout the whole questionnaire, a dropout button was implemented on each page. In both conditions, this button led to the same page that fully compliant participants reached at the end of the questionnaire. Reactance was measured with a self-constructed four-item reactance scale. To determine answer quality, we used self-report for faking as well as the analysis of answers to open ended questions. Results: Zero-order effects showed that FA increased state reactance and questionnaire dropout as well as it reduced answer length in open-ended questions. Mediation analysis (Condition -> state reactance -> dropout/answer quality) supported the hypothesis of reactance as an underlying psychological mechanism behind negative FA effects on data quality. Added Value: This is the first study which offers statistical evidence for the often proposed reactance effect influencing response behavior. This offers a base for a deeper psychological reflection of the use of the FA-option. [less ▲]

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See detailA Change Management Approach in Product Lines for Use Case-Driven Development and Testing
Hajri, Ines UL; Göknil, Arda UL; Briand, Lionel UL

Poster (2017, March)

In this paper, driven by industrial needs, we present a change management approach for product lines within the context of use case-driven development and testing. As part of the approach, we first ... [more ▼]

In this paper, driven by industrial needs, we present a change management approach for product lines within the context of use case-driven development and testing. As part of the approach, we first provide a modeling method to support variability modeling in Product Line (PL) use case diagrams, specifications, and domain models, intentionally avoiding any reliance on feature models and thus avoiding unnecessary modeling and traceability overhead. Then, we introduce a use case-driven configuration approach based on the proposed modelling method to automatically generate Product Specific (PS) use case and domain models from the PL models and configuration decisions. Building on this, we provide a change impact analysis approach for evolving configuration decisions in PL use case models. In addition, we plan to develop a change impact analysis approach for evolving PL use case models and an automated regression test selection technique for evolving configuration decisions and PL models. [less ▲]

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See detailVisuo-spatial abilities are key for children’s verbal number skills
Cornu, Véronique UL; Martin, Romain UL; Hornung, Caroline

Poster (2017, February 22)

Verbal number skills (i.e. counting and number naming) are milestones in numerical development. The aim of the present study was to clarify the role of different verbal abilities (VA) and visuo-spatial ... [more ▼]

Verbal number skills (i.e. counting and number naming) are milestones in numerical development. The aim of the present study was to clarify the role of different verbal abilities (VA) and visuo-spatial abilities (VSA) in the development of these verbal number skills in kindergarten. We recruited 152 children (mean age: 5.8 years) and administered different measures of VA (e.g. phonological awareness, pseudoword recall) and of VSA (e.g. spatial perception, copying) to assess their contribution to verbal number skills. Firstly, we computed two independent regression models, a “VA only” model explaining 23% of variance, and a “VSA only” model explaining 38% of variance. Adding verbal measures to the “VSA only” model does not lead to a significant increase in R2. Our results show that VSA, rather than VA, contribute to a larger extent to children’s verbal number skills. Intriguingly, the development of verbal number skills builds on VA, but more importantly on VSA. These results are potentially informative for the conception early mathematics interventions. [less ▲]

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See detailProject NUMTEST; Assessing basic number competence without language
Greisen, Max UL; Schiltz, Christine UL; Hornung, Caroline et al

Poster (2017, February 20)

While numerical skills are fundamental in modern societies, some estimated 5-7% of children suffer from a mathematical learning disorder, called developmental dyscalculia (DD). Nevertheless, universally ... [more ▼]

While numerical skills are fundamental in modern societies, some estimated 5-7% of children suffer from a mathematical learning disorder, called developmental dyscalculia (DD). Nevertheless, universally valid diagnostic instruments are still lacking, as all current DD test batteries are based on language instructions. Consequently their measurements are tightly linked to the specific language context of test administration and thus their results cannot easily be compared across countries. The present study is the first pilot study of a research project that aims to develop a test for basic math abilities that does not rely on language instruction and minimizes language use. To this aim, video and animation based instructions were implemented on touchscreen devices. A first version of the application has been tested with a sample of first grade children in Luxembourg’s fundamental schools, of which half used the same application but with traditional German instructions. First results indicate that performance in the experimental group was similar to the control group using verbal instructions. Relationships between linguistic background and the sample’s performance on one hand and qualitative usability aspects of nonverbal task instruction and tablet use with young children will be discussed. [less ▲]

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See detailAssessing the cerebral correlates of non-symbolic number processing with fast periodic visual stimulation
Guillaume, Mathieu UL; Mejias, Sandrine; Rossion, Bruno et al

Poster (2017)

Some authors recently challenged the claim that numerical processes specifically handle non-symbolic magnitudes and they alternately suggested that general visual and/or control executive processes could ... [more ▼]

Some authors recently challenged the claim that numerical processes specifically handle non-symbolic magnitudes and they alternately suggested that general visual and/or control executive processes could explain performance in number comparison tasks. To further investigate this issue, we set up an EEG paradigm in which we recorded neural responses to the passive viewing of different arrays of basic visual forms. The stimuli sequence followed a fast and sinusoidal contrast modulation at the frequency of 10Hz (ten items per second). Visual properties of elements randomly changed from item to item, but their number was manipulated: in a control condition, arrays always contained the same number, and in the experimental conditions, the number periodically changed (each eight iteration, at 1.25Hz). We varied the numerical ratio between the frequent and the rare number throughout the experimental conditions. We recorded significant responses on occipital and parietal electrodes to the oddball frequency and its harmonics during our experimental conditions. Crucially, the strength of the signal was proportionally larger when the numerical ratio was larger. The results suggest that implicit and passive viewing of quick sequence of arrays was sufficient to automatically elicit neural synchronisation to numerical magnitudes without any explicit involvement of higher general cognitive processes. [less ▲]

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See detailLangzeitkonsequenzen von frühkindlichem Stress
Schaan, Violetta UL; Schulz, André UL; Vögele, Claus UL

Poster (2017)

Traumatische Belastungen während der Kindheit können das Risiko für die Entwicklung unsicherer Bindungsstile erhöhen, die bereits mit langfristigen psychischen und körperlichen Gesundheitsproblemen in ... [more ▼]

Traumatische Belastungen während der Kindheit können das Risiko für die Entwicklung unsicherer Bindungsstile erhöhen, die bereits mit langfristigen psychischen und körperlichen Gesundheitsproblemen in Beziehung gebracht wurden. Die zugrundeliegenden Prozesse sind allerdings noch weitestgehend unklar. Wir präsentieren zwei Studien, die den Zusammenhang zwischen kindlichem Stress und Gesundheit im Erwachsenenalter sowie Körperwahrnehmung und Gedächtnisfähigkeit untersuchen. In der ersten Studie nahmen 199 Teilnehmer an einer Onlineumfrage teil, bei der Gesundheit, frühkindliches Trauma, Resilienz und Zurückweisungssensitivität gemessen wurden. Teilnehmer mit geschiedenen Eltern berichteten erhöhte psychische Belastungswerte, kindliches Trauma, Zurückweisungssensitivität und weniger Resilienz. Die Beziehung zwischen elterlicher Scheidung und psychischer Gesundheit konnte vollständig durch diese vier Faktoren erklärt werden (Varianzaufklärung 44%). In einer zweiten Studie wurden bei 60 Teilnehmern verschiedene Selbstbericht-Parameter erhoben und die Gedächtnis- und Interozeptionsfähigkeit vor und nach einem Stresstest untersucht. Erwachsene mit einer Vorgeschichte von elterlicher Trennung berichteten mehr bindungsbezogene Angst und Vermeidung als Kontrollpersonen. Das Erlebnis einer elterlichen Scheidung war negativ mit der Gedächtnisleistung nach dem Stresstest korreliert. Weiterhin weisen die Ergebnisse auf einen quadratischen Zusammenhang zwischen Stress und Interozeptionsfähigkeit hin. [less ▲]

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See detailSingle station Monitoring of Volcanoes Using Seismic ambient noise
De Plaen, Raphaël UL; Lecocq, Thomas; Caudron, Corentin et al

Poster (2016, December 16)

Detailed reference viewed: 44 (4 UL)
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Peer Reviewed
See detailImage to analysis pipeline: single and double balloons kyphoplasty
Baroli, Davide UL; Hauseux, Paul UL; Hale, Jack UL et al

Poster (2016, December 12)

In this work, we present a semi-automatic pipeline from image to simulation of a patient fractured vertebra after the kyphoplastic augmentation with two balloons. In this procedure, the CT-scan medical ... [more ▼]

In this work, we present a semi-automatic pipeline from image to simulation of a patient fractured vertebra after the kyphoplastic augmentation with two balloons. In this procedure, the CT-scan medical image are pre-processed using open-source software Slice3D for segmentation and 3D reconstruction operation. Then, using geometric processing the 3D surface geometry is enhanced to avoid degenerate element and trigging phenomena on vertebra and cement area. We perform a finite element analysis to evaluate the risk of subsequent vertebral fracture. Finally using Monte-Carlo technique, we assess the propagation of uncertainty of material parameter on the evaluation of this risk. Based on the developed semi-automatic pipelines, it is possible to perform a patient-specific simulation that assesses the successful of kyphoplasty operation. [less ▲]

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See detailBayesian inference for parameter identification in computational mechanics
Rappel, Hussein UL; Beex, Lars UL; Hale, Jack UL et al

Poster (2016, December 12)

Detailed reference viewed: 79 (7 UL)
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See detailReal-time error control for surgical simulation
Bui, Huu Phuoc UL; Tomar, Satyendra UL; Courtecuisse, Hadrien et al

Poster (2016, December 12)

Objective: To present the first real-time a posteriori error-driven adaptive finite element approach for real-time simulation and to demonstrate the method on a needle insertion problem. Methods: We use ... [more ▼]

Objective: To present the first real-time a posteriori error-driven adaptive finite element approach for real-time simulation and to demonstrate the method on a needle insertion problem. Methods: We use corotational elasticity and a frictional needle/tissue interaction model based on friction. The problem is solved using finite elements within SOFA. The refinement strategy relies upon a hexahedron-based finite element method, combined with a posteriori error estimation driven local $h$-refinement, for simulating soft tissue deformation. Results: We control the local and global error level in the mechanical fields (e.g. displacement or stresses) during the simulation. We show the convergence of the algorithm on academic examples, and demonstrate its practical usability on a percutaneous procedure involving needle insertion in a liver. For the latter case, we compare the force displacement curves obtained from the proposed adaptive algorithm with that obtained from a uniform refinement approach. Conclusions: Error control guarantees that a tolerable error level is not exceeded during the simulations. Local mesh refinement accelerates simulations. Significance: Our work provides a first step to discriminate between discretization error and modeling error by providing a robust quantification of discretization error during simulations. [less ▲]

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See detailError analysis of Tide Gauge Benchmark Monitoring (TIGA) Analysis Center stacked solutions
Hunegnaw, Addisu UL; Teferle, Felix Norman UL; Abraha, Kibrom Ebuy UL et al

Poster (2016, December 12)

In 2013 the International GNSS Service (IGS) Tide Gauge Benchmark Monitoring (TIGA) Working Group (WG) started their reprocessing campaign, which proposes to re-analyze all relevant Global Positioning ... [more ▼]

In 2013 the International GNSS Service (IGS) Tide Gauge Benchmark Monitoring (TIGA) Working Group (WG) started their reprocessing campaign, which proposes to re-analyze all relevant Global Positioning System (GPS) observations from 1995 to the end of 2013. This re-processed dataset will provide high quality estimates of land motions, enabling regional and global high-precision geophysical/geodetic studies. Several of the individual TIGA Analysis Centers (TACs) have completed processing the full history of GPS observations recorded by the IGS global network, as well as, many other GPS stations at or close to tide gauges, which are available from the TIGA data center at the University of La Rochelle (www.sonel.org). The TAC solutions contain a total of over 700 stations. This study focuses on the evaluations of any systematic error present in the three TIGA analysis center (TAC) SINEX solutions: the British Isles continuous GNSS Facility – University of Luxembourg consortium (BLT), the GeoForschungsZentrum (GFZ) Potsdam, and of the University of La Rochelle (ULR). We have analyzed the residual position time series of the individual TAC a combination of automatic and manual discontinuity identification, applying a post-seismic deformation model adopted from ITRF2014 for those stations that are affected by earthquakes, followed by the stacking of the daily solution of the individual TAC into a long term linear frame. We have carried out the error analysis using the Combination and Analysis of Terrestrial Reference Frame (CATREF) software package. The TIGA Combination Centre (TCC) at the University of Luxembourg (UL) is responsible for providing a combined solution with a global set of vertical land movement estimates. [less ▲]

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See detailElastography under uncertainty
Hale, Jack UL; Farrell, Patrick; Bordas, Stéphane UL

Poster (2016, December 12)

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See detailOn the Impact of Multi-GNSS Solutions on Satellite Products and Positioning
Abraha, Kibrom Ebuy UL; Teferle, Felix Norman UL; Hunegnaw, Addisu UL et al

Poster (2016, December 12)

In Global Navigation Satellite System (GNSS) coordinate time series unrecognised errors and un-modelled (periodic) effects may bias non-linear motions induced by geophysical signals. Those spurious ... [more ▼]

In Global Navigation Satellite System (GNSS) coordinate time series unrecognised errors and un-modelled (periodic) effects may bias non-linear motions induced by geophysical signals. Those spurious signals can be caused either due to un-modelled long periodic signals or propagation of sub-daily signals into the time series. Understanding and mitigating these errors is vital to reduce biases and on revealing subtle geophysical signals. Mostly, the spurious signals are caused by unmodelled errors which occur due to the draconitic years, satellite ground repeats and absorption into resonant GNSS orbits. Accordingly, different features can be observed in GNSS-derived products from different single-GNSS or combined-GNSS solutions. To assess the nature of periodic signals on station coordinate time series Precise Point Positioning (PPP) solutions are generated using the Bernese GNSS Software V5.2. The solutions consider only GPS, only GLONASS or combined GPS+GLONASS (GNSS) observations. We assess the periodic signals of station coordinates computed using the combined International GNSS Service (IGS) and four of its Analysis Centers (ACs) products. [less ▲]

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See detailPoster: LuST-LTE: A Simulation Package for Pervasive Vehicular Connectivity
Derrmann, Thierry UL; Faye, Sébastien UL; Frank, Raphaël UL et al

Poster (2016, December 08)

Recent technological advances in communication technology have provided new ways to understand human mobility. Connected vehicles with their rising market penetration are particularly representative of ... [more ▼]

Recent technological advances in communication technology have provided new ways to understand human mobility. Connected vehicles with their rising market penetration are particularly representative of this trend. They become increasingly interesting, not only as sensors, but also as participants in Intelligent Transportation System (ITS) applications. More specifically, their pervasive connectivity to cellular networks enables them as passive and active sensing units. In this paper, we introduce LuST-LTE, a package of open-source simulation tools that allows the simulation of vehicular traffic along with pervasive LTE connectivity. [less ▲]

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See detailUncertainty quantification for soft tissue biomechanics
Hauseux, Paul UL; Hale, Jack UL; Bordas, Stéphane UL

Poster (2016, December)

Detailed reference viewed: 125 (17 UL)
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See detailGame-Theoretic Framework for Integrity Verification in Computation Outsourcing
Pejo, Balazs UL; Tang, Qiang

Poster (2016, November 03)

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See detailEfficient Learning of Communication Profiles from IP Flow Records
Hammerschmidt, Christian UL; Marchal, Samuel; Pellegrino, Gaetano et al

Poster (2016, November)

The task of network traffic monitoring has evolved drastically with the ever-increasing amount of data flowing in large scale networks. The automated analysis of this tremendous source of information ... [more ▼]

The task of network traffic monitoring has evolved drastically with the ever-increasing amount of data flowing in large scale networks. The automated analysis of this tremendous source of information often comes with using simpler models on aggregated data (e.g. IP flow records) due to time and space constraints. A step towards utilizing IP flow records more effectively are stream learning techniques. We propose a method to collect a limited yet relevant amount of data in order to learn a class of complex models, finite state machines, in real-time. These machines are used as communication profiles to fingerprint, identify or classify hosts and services and offer high detection rates while requiring less training data and thus being faster to compute than simple models. [less ▲]

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See detailFacteurs psychologiques, cognitifs et les influences contextuelles dans la douleur et la souffrance liée à la douleur
Bustan, Smadar; Gonzalez-Roldan, Ana Maria; Schommer, Christoph UL et al

Poster (2016, November)

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See detailBehavioral Clustering of Non-Stationary IP Flow Record Data
Hammerschmidt, Christian UL; Marchal, Samuel; State, Radu UL et al

Poster (2016, October)

Detailed reference viewed: 68 (5 UL)
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See detailPOSTER: Fingerprinting Tor Hidden Services
Mitseva, Asya UL; Panchenko, Andriy UL; Lanze, Fabian et al

Poster (2016, October)

Detailed reference viewed: 157 (25 UL)
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See detailDifferent aspects of spatial skills and their relation to early mathematics
Cornu, Véronique UL; Hornung, Caroline; Schiltz, Christine UL et al

Poster (2016, September 29)

We aimed at investigating the predictive role of spatial skills for arithmetic and number line estimation in kindergarten children (N = 125). Several studies highlighted the relation between spatial ... [more ▼]

We aimed at investigating the predictive role of spatial skills for arithmetic and number line estimation in kindergarten children (N = 125). Several studies highlighted the relation between spatial skills and mathematics. However, due to their non-unitary nature, different aspects of spatial skills need to be differentiated to clarify the relative importance of different aspects of spatial skills for mathematics. In the present study, at time 1, a spatial perception task, a spatial visualization task and visuo-motor integration task were administered to assess different aspects of spatial skills. Furthermore we assessed domain-specific skills and verbal domain-general skills. Four months later, the same children performed an arithmetic task and a number line estimation task to evaluate how the abilities measured at time 1 predict early mathematics. Hierarchical regression modelling revealed that children’s performance on the spatial perception task was predictive of their performance in both arithmetic and number line estimation, whereas visuo-motor integration and knowledge of the Arabic numerals significantly predicted arithmetic. The predictive relation between spatial perception and arithmetic was partially mediated by the number line estimation task. Our findings emphasize the role of spatial skills, notably spatial perception, in mathematical development. These results reveal the importance to differentiate within the construct of spatial skills when studying their role in numerical development. The development and implementation of pre-school interventions fostering children’s spatial perception and visuo-motor integration might thus be a promising approach for providing children with a sound foundation for later mathematical learning. [less ▲]

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See detailCoP Luxembourg
Böwen, Petra UL; Dujardin, Céline UL; Pissinger, Simone

Poster (2016, September 05)

Detailed reference viewed: 67 (8 UL)
Peer Reviewed
See detailAge modulates the relation between number-space associations and arithmetical abilities in elementary school children
Georges, Carrie UL; Hoffmann, Danielle UL; Schiltz, Christine UL

Poster (2016, September)

Evidence for number-space associations comes from the SNARC effect, consisting in faster RTs to small/large digits with the left/right hand respectively. In adults, number-space associations relate to ... [more ▼]

Evidence for number-space associations comes from the SNARC effect, consisting in faster RTs to small/large digits with the left/right hand respectively. In adults, number-space associations relate to mathematical proficiency in that individuals with weaker arithmetic performances feature stronger SNARC effects (Hoffmann et al., 2014). However, in children far less is known about number-space associations and how they affect arithmetic performance. We therefore investigated the relationship between the classical parity SNARC effect and mathematical proficiency, assessed using the Heidelberger Rechentest, in elementary school children aged 8-11 years (n=55, mean=9.5). Overall, the parity SNARC regression slopes (-11.37, p<.001) negatively correlated with HRT arithmetical (r=-.28, p=.04; even when controlling for parity judgment RTs: r=-.37, p=.01), but not HRT visuo-spatial subscale scores (r=-.03, p=.82), indicating better arithmetic performances with stronger number-space associations. However, this relation was significantly moderated by age, since the interaction between the parity SNARC effect and age accounted for a significant proportion of the variance in HRT arithmetical scores (ΔR2=.07, b=0.26, t(51)=2.29, p=.03). A significant negative association was observed only in younger children (b=-0.35, t=-3.49, p=.001) aged below 9.5 years (n=29), while the SNARC effect did not relate to arithmetic performance in the remaining older children. This suggests that number-space associations are beneficial for arithmetic performance at relatively early stages of mathematical learning. During the course of mathematical development in childhood, number-space associations then turn superfluous for arithmetic achievement until they possibly become interfering in young adults, who have reached the peak of their developmental trajectory. [less ▲]

Detailed reference viewed: 17 (4 UL)
See detailEnergy fractionalization after single electron injection into an interacting helical liquid
Calzona, Alessio UL; Acciai, Matteo; Carrega, Matteo et al

Poster (2016, September)

Detailed reference viewed: 22 (2 UL)
See detailGeneric Helical Liquids: Theory & Applications
Rod, Alexia UL; Dolcetto, Giacomo UL; Rachel, Stephan et al

Poster (2016, August 23)

Detailed reference viewed: 33 (13 UL)
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See detailOn the Properties of Zenith Total Delay Time Series from Reprocessed GPS Solutions
Klos, Anna; Teferle, Felix Norman UL; Hunegnaw, Addisu UL et al

Poster (2016, July 29)

Global Positioning System observations from stations in regional and global networks have proven to sense the conditions of the atmosphere, especially the water vapour content of the troposphere. Zenith ... [more ▼]

Global Positioning System observations from stations in regional and global networks have proven to sense the conditions of the atmosphere, especially the water vapour content of the troposphere. Zenith Total Delay (ZTD) derived during the processing of GPS data is a measure of the total atmospheric delay along the signal path between satellite and receiver antennas and arises mostly from the hydrostatic and wet parts of the atmosphere. Having taken surface pressure and temperature into account, ZTD can be converted into an estimate of the Integrated Water Vapour (IWV) content of the atmosphere, which when derived from homogenously reprocessed GPS observations, is emerging as an important parameter in the monitoring of climate change. Especially, the long-term trend and variations in IWV together with their associated uncertainties are of high interest as atmospheric water vapour is the dominant greenhouse gas. To date the trend estimates and their uncertainties are widely determined with assumption that the stochastic properties of the time series follow a random, ie. white noise, process. However, if ZTD and IWV are directly linked to climate processes, one would expect that the underlying noise process has similar character to that found in other climate parameters, which have been modelled by means of an autoregressive process. If this proves to be true, the trend estimates and their uncertainties in ZTD and IWV may have been underestimated up to this day of an order of magnitude. In this research, we examine the properties of both deterministic and stochastic parameters of the ZTDs that were estimated by the consortium of the British Isles continuous GNSS Facility (BIGF) and the University of Luxembourg TIGA Analysis Centres (BLT) for GPS data collected by a global tracking network of more than 700 stations (repro2 solution). The analysis has been started with the homogenisation of the ZTD time series, which is an important task to provide homogeneity over the long-term. Here we used all previously reported discontinuities for a single station along with those added after manually inspecting the time series. This procedure did lead to a total number of 2505 discontinuities for this data set. Next, all significant oscillations were identified with spectral analysis and thereafter modelled with a Least-Squares Method. The residuals were subjected to noise analysis with different stochastic models. The results showed that an autoregressive model of fourth order combined with a white noise process is the optimal model for the ZTD time series. Finally, we provide an optimum evaluation of the ZTD trends and their uncertainties for selected climate zones, which were established according to the Köppen-Geiger climate classification. [less ▲]

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See detailFatherhood Desires and Intentions: A Comparison of Childless Gay and Straight Men in Germany
Kranz, Dirk; Busch, Holger; Niepel, Christoph UL

Poster (2016, July)

Detailed reference viewed: 38 (1 UL)
Peer Reviewed
See detailAnnotating and Georeferencing of Digitized Early Maps
Höhn, Winfried UL; Schommer, Christoph UL

Poster (2016, July)

Original early maps are usually only accessible for a small group of researchers and librarians because they are very old and sensitive, and could be easily destroyed. However, they are a valuable ... [more ▼]

Original early maps are usually only accessible for a small group of researchers and librarians because they are very old and sensitive, and could be easily destroyed. However, they are a valuable knowledge source for historical research, because they are also political and cultural evidences of its time. In the age of Digital Humanities, online access and information search in digitized historical documents and early maps allows people from all over the world to work with such artefacts of cultural heritage. However, the digitization solely generates images of the artefacts without any access to the semantics of the documents. [less ▲]

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See detailThe effect of a French intervention on children´s spelling of morphosyntactic agreement.
Bilici, Natalia UL; Ugen, Sonja UL; Weth, Constanze UL

Poster (2016, July)

The purpose of our project MorphoSyn is to gain insights into the morphosyntactic processing involved in spelling in second languages. We conduct our study in the complex language context of Luxembourg ... [more ▼]

The purpose of our project MorphoSyn is to gain insights into the morphosyntactic processing involved in spelling in second languages. We conduct our study in the complex language context of Luxembourg which has two written school languages (German and French) and a large variety languages spoken at children´s home. More specifically, we investigate how an explicit teaching of morphosyntactic structures in written German and French enhance the spelling competence of 5th grade students. During our intervention we focus on two orthographic features: the capitalisation of nouns in German and subject-verb agreement and the agreement within nouns phrases in French. Studies from Germany and France show that the acquisition of these features pass quite difficultly, because they are inaudible and, to grasp them, students need knowledge that goes beyond phoneme-grapheme correspondences. We predicted that our multilingual pupils will encounter the same problems that have been detected for French and German monolingual children. Our recently conducted pilot study confirmed this assumption: many children still omit plural/feminine markers in French and fail to capitalize abstract nouns or nominalisations in German. Our paper will present the outcome of the pre-test administrated to 250 Luxembourgish students (listening comprehension and dictation in German and French). It will show the orthographic skills pupils have acquired during primary school in their school languages German and French and indicate how far they are using morphosyntactic information while spelling. [less ▲]

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See detailInterventions addressing subjective well-being in ageing: Promissing approaches on individual and societal level
Boll, Thomas UL; Ferring, Dieter UL

Poster (2016, June)

Subjective well-being (SWB) in aging is important not only as an indicator of positive aging, but also because of its effects on relevant outcomes for the person (e.g., health) and the community (e.g ... [more ▼]

Subjective well-being (SWB) in aging is important not only as an indicator of positive aging, but also because of its effects on relevant outcomes for the person (e.g., health) and the community (e.g., involvements). This raises the question of how SWB of older people can be improved through interventions. Our contribution focusses on three domains for improving SWB: Optimization of resources (e.g., financial situation, autonomy), help with critical life events (e.g., widowhood, disablement), and support at the end of life. We consider reasons for optimizing SWB in these areas as well as the theoretical and empirical foundation for interventions. Among them are (1) bottom-up approaches regarding the link between domain-specific SWB (e.g., regarding health, financial situation, social relationships) and global SWB, (2) Coping approaches to critical life events frequently occuring in old age (e.g., widowhood, disablement) and (3) research on terminal decline of SWB. Against this background principal possibilities of optimizing SWB in these domains are delineated and both individual and societal (e.g., communal, national) level interventions are described. [less ▲]

Detailed reference viewed: 95 (6 UL)
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See detailDifférences inter‐ et intraindividuelles en besoin de cognition
Keller, Ulrich UL; Strobel, Anja; Martin, Romain UL et al

Poster (2016, June)

Detailed reference viewed: 75 (9 UL)
Peer Reviewed
See detailEarly life adversity associates with increased depressive symptoms and few active T cells in adulthood
Elwenspoek, Martha; Schaan, Violetta UL; Hengesch, Xenia et al

Poster (2016, June)

Detailed reference viewed: 74 (6 UL)
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See detailDéveloppement d’un instrument de dépistage des précurseurs cognitifs pour l’apprentissage scolaire dans un contexte multilingue
Cornu, Véronique UL; Hornung, Caroline

Poster (2016, June)

Nombreuses études ont pu constater que les aptitudes et les apprentissages précoces influencent les apprentissages académiques ultérieurs. La valeur prédictive de différentes fonctions cognitives à l’âge ... [more ▼]

Nombreuses études ont pu constater que les aptitudes et les apprentissages précoces influencent les apprentissages académiques ultérieurs. La valeur prédictive de différentes fonctions cognitives à l’âge préscolaire est un sujet toujours vivement discuté. L'apprentissage des mathématiques, de la lecture et de l'écrit sont soutenues par des fonctions cognitives telles que les capacités pré-numériques, le langage, les fonctions visuo-spatiales, les fonctions exécutives dont la mémoire de travail, la vitesse de traitement et la raisonnement logique. Néanmoins, seulement peu de données scientifiques sont actuellement disponibles sur l’apport de ces différentes fonctions cognitives aux apprentissages scolaires dans un contexte multilingue comme celui du Luxembourg. Au Luxembourg environ 35 % des élèves scolarisés à l'école maternelle parlent Luxembourgeois à la maison. La plupart des enfants parlent d'autres langues voire plusieurs langues au sein de leur famille. A l'école maternelle les enfants apprennent le Luxembourgeois pendant 2-3 ans. Ensuite en 1ère année de l'enseignement fondamental primaire public, tous les enfants sont alphabétisés en Allemand. Et ce n'est qu'un an plus tard que le Français s'ajoute aux apprentissages scolaires. L'apprentissage des langues est un projet ambitieux au Luxembourg et les résultats nationaux ont montré que 42 % des élèves en 3e année primaire (CE2) n'ont malheureusement pas obtenu le niveau minimal à atteindre visé par le plan d'étude en 2013 (Hornung, Hoffmann, Lorphelin, Gamo, Ugen, Fischbach, & Martin, 2015). Le but est de développer un instrument qui s'adapte au contexte scolaire multilingue et qui permet de mesurer ces précurseurs cognitifs d’une manière valide. Ce projet vise à mieux comprendre comment différentes capacités cognitives précoces influencent les différents apprentissages scolaires dans un contexte scolaire multilingue chez l’enfant de 4 à 7 ans et les résultats de ce projet pourront servir comme base pour pouvoir développer des outils d’intervention visant à stimuler le développement de ces précurseurs dans un contexte multilingue. La présente batterie de tests inclut plusieurs épreuves brèves individuelles pour évaluer les performances numériques et visuo-spatiales, la capacité d'inhibition verbale et d'inhibition motrice, l'empan de la mémoire de travail verbale et visuo-spatiale, la flexibilité verbale, la vitesse de traitement, la conscience phonologique, la discrimination visuelle et le vocabulaire expressif chez l’enfant de 4 à 7 ans. Ces petites épreuves visent à évaluer ces différents précurseurs cognitifs de l’apprentissage scolaire et elles ont été développées et adaptées spécifiquement pour le contexte préscolaire suite à un pilotage avec la population cible. Dans une première phase, les relations entre ces différentes épreuves seront étudiées pour pouvoir concrétiser notre compréhension sur l’interrelation de ces différents précurseurs cognitifs. Afin de pouvoir évaluer la valeur prédictive de ces différentes fonctions cognitives, une approche longitudinale est visée. Nous avons prévu de mettre en relation les résultats obtenus au préscolaire (Phase I) avec les résultats de ces mêmes enfants obtenus lors des «épreuves standardisées» du monitoring scolaire au Luxembourg, réalisées en première année de l’école primaire (CP en France) (Phase II). [less ▲]

Detailed reference viewed: 108 (11 UL)
See detailChemical stability of the Cu2SnS3/Mo interface
De Wild, Jessica UL; Robert, Erika UL; Dale, Phillip UL

Poster (2016, June)

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See detailA PRELIMINARY STUDY ON THE STABILITY OF PARTICLE LADEN JETS THROUGH A FULLY COUPLED CFD-DEM SOLVER
Peters, Bernhard UL; Pozzetti, Gabriele UL

Poster (2016, May 22)

Jets are widely used in engineering applications. In material machinery, hydro-transportation systems as well as in chemical industry it is common to deal with a dispersed solid phase interacting with the ... [more ▼]

Jets are widely used in engineering applications. In material machinery, hydro-transportation systems as well as in chemical industry it is common to deal with a dispersed solid phase interacting with the jet, and therefore creating a so-called slurry-jet or particle-laden jet. The stability of a jet is a key issue for many of these processes, still the underlying physics of this turbulent multiphase flow is highly complicated. Conventional CFD approaches have been proven satisfying for the study of the stability of two-phase jets. When a solid dispersed phase is present in the system, the stability problem gets more complicated and dependent on the solid phase dynamic. A possible solution for the problem is to extend the CFD solver capability through a correct coupling with a DEM solver. In this work a preliminary investigation on the potentialities of this kind of approach is presented and compared with a pure CFD approach. In particular the effect of the presence of differently sized particles in the jet is outlined and the influence of particle properties and concentration is investigated. Finally some considerations about the computational cost of different methods are proposed. The fluid phases are solved through an Eulerian finite volume (FV) multiphase solver based on the OpenFoam® libraries, and coupled with the XDEM code in order to treat the dispersed phase in a Lagrangian way. [less ▲]

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See detailStudy of space weather impact on Antarctica ionosphere from GNNS data
Bergeot, Nicolas; Chevalier, J.-M.; Bruyninx, Carine et al

Poster (2016, April 29)

The impact of solar activity on the ionosphere at polar latitudes is not well known compare to low and mid-latitudes due to lack of experimental observations, especially over Antarctica. Consequently, one ... [more ▼]

The impact of solar activity on the ionosphere at polar latitudes is not well known compare to low and mid-latitudes due to lack of experimental observations, especially over Antarctica. Consequently, one of the present challenges of the Space Weather community is to better characterize (1) the climatological behavior of the polar ionosphere in response to variations of the solar activity and (2) the different response of the ionosphere at high latitudes during extreme solar events and geomagnetic storms. For that, the combination of GNSS measurements (e.g. GPS, GLONASS and Galileo) on two separate frequencies allows determining the ionospheric delay between a ground receiver and a satellite. This delay is function of the integrated number of electrons encountered in the ionosphere along the signal ray path, called the Total Electron Content (TEC). It is thus possible to study the behavior of ionospheric TEC at different time and spatial scales from the observations of a network of permanent GNSS stations. In the frame of GIANT-LISSA and IceCon projects we installed since 2009 five GNSS stations around the Princess Elisabeth station. We used these stations additionally to other stations from the IGS global network to estimate the ionospheric TEC at different locations over Antarctica. This study presents this regional data set during different solar activity levels and discusses the different climatological behaviors identified in the ionosphere at these high latitudes. Finally, we will show few examples of typical TEC disturbances observed during extreme solar events. [less ▲]

Detailed reference viewed: 137 (18 UL)
Peer Reviewed
See detailExperimental Lifetime Investigation of Series Connected Li-ion Cells at Different Operation Strategies
Brühl, Manuel UL; Sauer, Dirk Uwe; Hadji-Minaglou, Jean-Régis UL

Poster (2016, April 26)

Battery systems consisting of serially connected cells suffer from uneven cell degradation. This phenomenon can be observed, even if li-ion cells of the same type and batch are cycled in a fixed voltage ... [more ▼]

Battery systems consisting of serially connected cells suffer from uneven cell degradation. This phenomenon can be observed, even if li-ion cells of the same type and batch are cycled in a fixed voltage window at the same temperature. The uneven cell degradation has a significant impact on the usable capacity of a battery system as the system capacity is limited by the capacity of the weakest cell. This issue reduces the battery lifetime and increases the costs. In a former work, li-ion cells were cycled individually and the different cell degradation could be observed significantly. In this work, aging tests are conducted with cells in series connected conditions to investigate the uneven cell degradation behavior. Cyclization of series connected cells could lead to a higher spread of cell degradation as weaker cells are deeper cycled. Three aging tests, each consisting of eight li-ion cells are conducted in this work. The eight cells of each test are cycled with the same current to investigate the aging behavior under comparable conditions as in a series connection. The first test is conducted to investigate the aging behavior of a conventional system with series connected cells and passive balancing. In the second and third test, the uneven cell degradation is actively compensated with the operation strategy of the balancing circuit. In the second test the voltage window are changed with respect to the cell’s state of health. In the third test the cell current of each cell is changed with respect to the cell’s state of health. Preliminary results show that cells in the first test suffer a bigger capacity diversion over time than cells in the second and third test. Such operation strategies could be implemented in real systems to reduce the different cell degradation and to prolong the systems lifetime. Further analysis and conclusions will be given on the conference poster. [less ▲]

Detailed reference viewed: 55 (5 UL)
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See detailCombination of Tide Gauge Benchmark Monitoring (TIGA) Analysis Center from repro2 solutions
Hunegnaw, Addisu UL; Teferle, Felix Norman UL

Poster (2016, April 19)

Recently the International GNSS Service (IGS) Tide Gauge Benchmark Monitoring (TIGA) Working Group (WG) has completed their repro2 solutions by re-analyzing the full history of all relevant Global ... [more ▼]

Recently the International GNSS Service (IGS) Tide Gauge Benchmark Monitoring (TIGA) Working Group (WG) has completed their repro2 solutions by re-analyzing the full history of all relevant Global Positioning System (GPS) observations from 1995 to 2015. This re-processed data set will provide high-quality estimates of vertical land movements for more than 700 stations, enabling regional and global high-precision geophysical/geodetic studies. All the TIGA Analysis Centres (TACs) have processed the observations recorded by GPS stations at or close to tide gauges, which are available from the TIGA Data Center at the University of La Rochelle (www.sonel.org) besides those of the global IGS core network used for its reference frame implementations. Following the recent improvements in processing models, strategies (http://acc.igs.org/reprocess2.html), this is the first complete reprocessing attempt by the TIGA WG to provide homogeneous position time series relevant to sea level changes. In this study we report on a first multi-year daily combined solution from the TIGA Combination Centre (TCC) at the University of Luxembourg (UL) with respect to the latest International Terrestrial Reference Frame (ITRF2014). Using GLOBK combination software package, we have computed a first daily combined solution from TAC solutions already available to the TIGA WG. These combinations allow an evaluation any effects of the individual TAC parameters and their influences on the combined solution with respect to the latest ITRF2014. Some results of the UL TIGA multi-year combinations in terms of geocentric sea level changes will be presented and discussedd [less ▲]

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Peer Reviewed
See detailApplications of the CPAL language to model, simulate and program Cyber-Physical Systems
Fejoz, Loïc; Navet, Nicolas UL; Sundharam, Sakthivel Manikandan UL et al

Poster (2016, April 12)

CPAL is a new language to model, simulate, verify and program Cyber-Physical Systems (CPS). CPAL serves to describe both the functional behaviour of activities (i.e., the code of the function itself) as ... [more ▼]

CPAL is a new language to model, simulate, verify and program Cyber-Physical Systems (CPS). CPAL serves to describe both the functional behaviour of activities (i.e., the code of the function itself) as well as the functional architecture of the system (i.e., the set of functions, how they are activated, and the data flows among the functions). CPAL is meant to support two use-cases. Firstly, CPAL is a development and design-space exploration environment for CPS with main features being the formal description, the editing, graphical representation and simulation of CPS models. Secondly, CPAL is a real-time execution platform. The vision behind CPAL is that a model is executed and verified in simulation mode on a workstation and the same model can be later run on an embedded board with a timing-equivalent run-time behaviour. The design and development of CPAL have been organized around a set of realistic case-studies that will be demonstrated during the demo session. [less ▲]

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See detailThe Combined Effect of Periodic Signals and Noise on the Dilution of Precision of GNSS Station Velocity Uncertainties
Klos, Anna; Olivares Pulido, German UL; Teferle, Felix Norman UL et al

Poster (2016, April 05)

Station velocity uncertainties determined from a series of Global Navigation Satellite System (GNSS) position estimates depend on both the deterministic and stochastic models applied to the time series ... [more ▼]

Station velocity uncertainties determined from a series of Global Navigation Satellite System (GNSS) position estimates depend on both the deterministic and stochastic models applied to the time series. While the deterministic model generally includes parameters for a linear and several periodic terms, the stochastic model is a representation of the noise character of the time series in form of a power-law process. For both of these models the optimal model may vary from one time series to another while the models also depend, to some degree, on each other. In the past various power-law processes have been shown to fit the time series and the sources for the apparent temporally-correlated noise were attributed to, for example, mismodelling of satellites orbits, antenna phase centre variations, troposphere, Earth Orientation Parameters, mass loading effects and monument instabilities. [less ▲]

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See detailTHE IMPACT OF LANGUAGE BACKGROUND ON BASIC MATH COMPETENCE
Poncin, Alexandre UL; Amandine, Van Rinsveld; Schiltz, Christine UL

Poster (2016, April 02)

German number word system inverts units and tens compared to the Arabic notation. This is not the case in French, which is more transparent regarding the Arabic number code. Evidence indicates that the ... [more ▼]

German number word system inverts units and tens compared to the Arabic notation. This is not the case in French, which is more transparent regarding the Arabic number code. Evidence indicates that the linguistic structure of number words can facilitate or impede numerical development (Zuber, Pixner, & Moeller, 2009). Moreover, in transcoding tasks more mistakes are made in non-transparent compared to transparent languages (Imbo, Vanden Bulcke, De Brauwer, & Fias, 2014). We used a new paradigm of transcoding task in which 28 French-speaking (FR) and 19 German-speaking (GE) 4th grade children had to listen two digits numbers. The new thing was that we manipulate the order of appearance of the units and the tens of the number in three conditions: Units-First (UF), Tens-First (TF) and Simultaneous (S). Then, the subjects had to choose the heard number among four numbers presented on the computer screen. Results sows that GE are globally slower than FR (F(1,45) = 3.95, p = .053). The largest difference was observed for the TF: (t(45) = -3.729, p = .001). Moreover, when the order of the number appearance was congruent with the number word system, the transcoding was faster in both languages. For GE the S condition was slower than TF condition (F(2,36) = 6.918, p = .008) and than UF condition (F(2,36) = 6.918, p = .003.). For FR, the TF was faster than S (F(2,54) = 69.419, p < .001) and UF (F(2,54) = 69.419, p < .001). All these data indicate that language structure qualitatively impacts on basic numerical tasks. [less ▲]

Detailed reference viewed: 22 (2 UL)
See detailGender impacts on business succession: Men, women, and the family company
Nelson, Dylan; Constantinidis, Christina UL; Bell, Deborah et al

Poster (2016, March 31)

Building on a previous study of the family business succession literature, showing that gender is considered conceptually only in the case of women, we aim to uncover the sons’ gender stories.

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Peer Reviewed
See detailAssessing spelling skills related to morphosyntax of German-French biliterate pupils in a multilingual educational context
Ugen, Sonja UL; Bilici, Natalia UL; Fayol, Michel UL et al

Poster (2016, March 12)

How do multilingual learners write spellings related to morphosyntactic information in German (capitalisation of nouns) and French (plural markers of nouns, adjectives and verbs)? Our talk presents the ... [more ▼]

How do multilingual learners write spellings related to morphosyntactic information in German (capitalisation of nouns) and French (plural markers of nouns, adjectives and verbs)? Our talk presents the construction and the items of a spelling test of German and French for multilingual 5th graders in Luxembourg (N=300) as well as the first results of both tests. It is the pre-test of a study that will analyse the processes of morphosyntactic agreement in spelling in the children’s first (German) and second (French) acquired language at school. It will further examine how their performances relate to their language background. The setting in Luxembourg is characterised by three school languages: While Luxembourgish is the language of pre-school, children are alphabetised in German and learn French from second grade on. German and French are second languages for most children. However, children have either a Germanic (Luxembourgish) or a Romance (Portuguese) background. The children performed spellings tests tailored to the specificities of each of the test languages but relying on comparable grammatical processes. The test framework will be presented in detail as well as first results. Based on the literature, we expect differences in performances for proper and abstract nouns as well as nominalisation with best performance for proper nouns. In French, we expect differences in performances according to the plural markers of nouns, adjectives and verbs with best performance for nouns. Additionally, we expect contextual effects of the target words within each language. Results will further be analysed according to the background language of the children. [less ▲]

Detailed reference viewed: 17 (0 UL)
See detailTheoretical Study of the Raman G Peak Intensity of Graphene
Reichardt, Sven UL; Wirtz, Ludger UL

Poster (2016, February 18)

Detailed reference viewed: 73 (8 UL)
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See detailA First Evaluation of the new GNSS Station Installations at the Tide Gauges of Walvis Bay and Lüderitz in the Republic of Namibia
Teferle, Felix Norman UL; Combrinck, Ludwig; Botha, Roelf et al

Poster (2016, February 11)

During September 2015 the Hartebeesthoek Radio Astronomy Observatory in collaboration with the University of Luxembourg installed two state-of-the-art continuous GNSS stations adjacent to the tide gauges ... [more ▼]

During September 2015 the Hartebeesthoek Radio Astronomy Observatory in collaboration with the University of Luxembourg installed two state-of-the-art continuous GNSS stations adjacent to the tide gauges of Walvis Bay and Lüderitz in the Republic of Namibia. These installations are the culmination of a four-year effort to get the stations established and the help of the Namibian Port Authority in this endeavour is much appreciated. The tide gauge at Walvis Bay (Global Sea Level Observing System (GLOSS) number 314) has a record in the Permanent Service for Mean Sea Level (PSMSL) Revised Local Reference (RLR) database (number 914) dating back to 1958 (data completeness 54%). The tide gauge at Lüderitz is not a GLOSS station but also has a PSMSL RLR record (number 911) since 1958 (data completeness 67%). Both tide gauges currently use a radar measurement unit and are operated by the Hydrographic Office of the South African Navy. They are the only sea level observations along a more than 3000 km stretch of the West African coast from Pointe Noire in the Republic of the Congo to Port Nolloth in the Republic South Africa, hence they form an important data source for sea level studies. The two continuous GNSS stations record observations from all visible GNSS satellites (GPS, GLONASS, BDS and Galileo) with a 1 second recording interval. The current installations support hourly data downloads, which are sufficient for most activities within the IGS, while the data have great potential to contribute not only to the TIGA working group but also to MGEX. In this study we present the first evaluation of the quality of the GNSS observations from the two new continuous GNSS stations for the first three months of operation. In the future we plan to make the data available to the scientific community. [less ▲]

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See detailTotal Impact of Periodic Terms and Coloured Noise on Velocity Estimates
Klos, Anna; Olivares, German; Teferle, Felix Norman UL et al

Poster (2016, February 05)

The uncertainties of velocity estimates for position time series of Global Navigation Satellite System (GNSS) stations are mainly affected by a misfit of the deterministic model applied to this data ... [more ▼]

The uncertainties of velocity estimates for position time series of Global Navigation Satellite System (GNSS) stations are mainly affected by a misfit of the deterministic model applied to this data. Insufficiently modelled seasonal signals will propagate into the stochastic model and falsify the results of the noise analysis besides the velocity estimates and their uncertainties. In this presentation we derived the General Dilution of Precision (GDP) of velocity uncertainties. We define this dilution as the ratio between the uncertainties of velocities determined when different deterministic and stochastic models are applied. In this way we discuss, referring to previously published results, how insufficiently modelled seasonal signals influence station velocity uncertainties with white and coloured noise. Using simulated and real data from selected (115) IGS (International GNSS Service) stations we show that the noise character affects GNSS data more than seasonals for time series longer than 9 years. [less ▲]

Detailed reference viewed: 35 (0 UL)
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See detailQuality assessment of Mulit-Year BLT Tide Gauge Benchmark Monitoring (TIGA) repro2 Solution
Hunegnaw, Addisu UL; Teferle, Felix Norman UL

Poster (2016, February)

Recently the International GNSS Service (IGS) Tide Gauge Benchmark Monitoring (TIGA) Working Group (WG) has completed their repro2 solutions by re-analyzeing the full history of all relevant Global ... [more ▼]

Recently the International GNSS Service (IGS) Tide Gauge Benchmark Monitoring (TIGA) Working Group (WG) has completed their repro2 solutions by re-analyzeing the full history of all relevant Global Positioning System (GPS) observations from 1995 to 2015. This re-processed data set will provide high-quality estimates of vertical land movements for more than 500 stations, enabling regional and global high-precision geophysical/geodetic studies. All the TIGA Analysis Centres (TACs) have mainly processed the GPS observations recorded by GPS stations at or close to tide gauges, which are available from the TIGA data centre at the University of La Rochelle (www.sonel.org). Following the recent improvements in processing models, strategies (http://acc.igs.org/reprocess2.html), this is the first complete re-processing attempt by the TIGA WG to provide homogeneous position time series relevant to sea level changes. In this study we report on a first multi-year daily combined solution from the TIGA Combination Centre (TCC) at the University of Luxembourg (UL) with respect to the latest International Terrestrial Reference Frame (ITRF2014). Using two independent combination software packages, CATREF and GLOBK, we have computed a first daily combined solution from TAC solutions already available for TIGA WG. These combinations allow an evaluation of any effects from the combination software and of the individual TAC parameters and their influences on the combined solution with respect to the latest ITRF2014. Some results of the UL TIGA multi-year combinations in terms of geocentric sea level changes will be presented and discussed. [less ▲]

Detailed reference viewed: 73 (14 UL)
Peer Reviewed
See detailCardinal and ordinal processing in spatial neglect
Sosson, Charlotte UL; di Luca, Samuel UL; Guillaume, Mathieu UL et al

Poster (2016, January)

Patients with spatial neglect do not only have difficulties in orienting attention in physical space but also in representational space, especially with respect to the mental representation of numbers ... [more ▼]

Patients with spatial neglect do not only have difficulties in orienting attention in physical space but also in representational space, especially with respect to the mental representation of numbers. Indeed, in a study by Zorzi et al. (2012) neglect patients were particularly slow when asked to compare the number 4 to the standard number 5, suggesting difficulties to process numbers on the left side of an internal standard. This difficulty was observed in a magnitude judgement, but not in a parity task, implying a dissociation between explicit and implicit processing of numerical magnitude. The present study aimed at replicating these findings and extending them to non-numerical sequences in order to complement the data obtained on bisection tasks (Zamarian, et al., 2007). Sixteen right-sided brain damaged patients with neglect (N+ =6; 4 females; all right handers; mean age: 55 +/- 8,7) and without neglect (N- =10; 2 females; all right hander; mean age: 48 +/- 6.2) participated in the study. They were administered the following tasks: a magnitude and a parity judgement task; an ordinal judgement task on numbers and on letters and a consonant/vowel classification task. For each task and each patient, a linear regression was computed in which the difference between the response times for the left effector (index finger) and the right effector (middle finger) was predicted by number magnitude. A negative slope will indicate the presence of a SNARC-like effect. We compared the negative slopes of the two patient groups using a Chi-square. Considering the proportion of SNARC-like effects, it appeared that, on one hand, N+ patients showed fewer SNARC-like effects than N- patients during magnitude judgements on numbers. Thus confirming the findings by Zorzi et al. (2012). On the other hand, N+ patients behaved similarly to N- patients for the parity judgements on numbers and for the order judgements both on numbers and letters. This last result suggest a dissociation between the spatial representation of magnitude and of order in N+ patients. These results point towards a specific impairment in explicit access to number magnitude in spatial hemineglect. [less ▲]

Detailed reference viewed: 59 (11 UL)
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See detailDiscrete mechanical models and upscaling techniques for discrete materials
Beex, Lars UL; Bordas, Stéphane UL

Poster (2016)

Numerous natural and man-made materials are essentially discrete structures at the mesoscale or microscale (see Fig. 1). Discrete mechanical models can be formulated to capture typical mechanical ... [more ▼]

Numerous natural and man-made materials are essentially discrete structures at the mesoscale or microscale (see Fig. 1). Discrete mechanical models can be formulated to capture typical mechanical phenomena arising from this discreteness. Failure in these materials, which often starts with the fracture of an individual bond, can be predicted based on the small-scale mechanics with these models. For failure, but also for non-local mechanics, no phenomenological descriptions are required in these models. This makes them more predictive than constitutive material models for this type of materials. [less ▲]

Detailed reference viewed: 70 (5 UL)
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Peer Reviewed
See detailDetecting Electricity Theft
Glauner, Patrick UL

Poster (2016)

Detailed reference viewed: 64 (11 UL)
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Peer Reviewed
See detailPoster: PREXT: Privacy Extension for Veins VANET Simulator
Emara, Karim Ahmed Awad El-Sayed UL

Poster (2016)

Preserving location privacy is an important aspect in vehicular ad-hoc networks. Although location privacy is thoroughly studied in the past decade, it is usually skipped in VANET simulators. In this ... [more ▼]

Preserving location privacy is an important aspect in vehicular ad-hoc networks. Although location privacy is thoroughly studied in the past decade, it is usually skipped in VANET simulators. In this paper, we propose a location privacy extension, PREXT, for Veins framework. Currently, PREXT supports seven privacy schemes of different approaches including silent period, context-based and cryptographic mix-zone. It can be also easily extended to include more schemes. It includes adversary modules that can eavesdrop vehicle messages and track their movements. This adversary is used in measuring the gained privacy in terms of several popular metrics such as entropy, traceability and pseudonym usage statistics. We utilize this extension to compare among different schemes in an urban scenario. [less ▲]

Detailed reference viewed: 39 (5 UL)
Peer Reviewed
See detailComplex problem solving and intelligence. A meta-analysis
Stadler, Matthias; Becker, N.; Gödker, M. et al

Poster (2016)

Detailed reference viewed: 28 (0 UL)
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Peer Reviewed
See detailSome Properties of Homogenous Trellis-Constrained Codes
Franck, Christian UL; Sorger, Ulrich UL

Poster (2016)

We consider Homogenous Trellis-Constrained Codes (HTCC), a generalization of Turbo-codes where all bits are constrained. No efficient decoding algorithm is known for these codes, so our results are ... [more ▼]

We consider Homogenous Trellis-Constrained Codes (HTCC), a generalization of Turbo-codes where all bits are constrained. No efficient decoding algorithm is known for these codes, so our results are primarily of theoretical interest. We propose a technique to derive an upper bound for the maximum-likelihood (ML) decoding of BSC errors. Our tech- nique is based on the weight distributions of the constituent codes and it can also be used when a specific number of errors e is known. We observe that with an ML-decoder some HTCC codes exhibit an error correcting performance close to that of random codes. For those codes we also observe a significant performance gap between ML-decoding and practical decoding based on belief-propagation. [less ▲]

Detailed reference viewed: 29 (5 UL)
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See detailMultiscale hydrogeological and hydrogeophysical approach to monitor vadose zone hydrodynamics of a karst system
Watlet, Arnaud; Poulain, Amaël; Francis, Olivier UL et al

Poster (2016)

The vadose zone of karst systems plays an important role on the water dynamics. In particular, temporary perched aquifers can appear in the subsurface due to changes of weather conditions, reduced ... [more ▼]

The vadose zone of karst systems plays an important role on the water dynamics. In particular, temporary perched aquifers can appear in the subsurface due to changes of weather conditions, reduced evapotranspiration and the vertical gradients of porosity and permeability. Although many difficulties are usually encountered when studying karst environments due to their heterogeneities, cave systems offer an outstanding opportunity to investigate vadose zone from the inside. We present a multi-scale study covering two years of hydrogeological and geophysical monitoring of the Lomme Karst System (LKS) located in the Variscan fold-and-thrust belt (Belgium), a region (∼3000 ha) that shows many karstic networks within Devonian limestone units. Hydrogeological data cover the whole LKS and involve e.g. flows and levels monitoring or tracer tests performed in both vadose and saturated zones. Such data bring valuable information on the hydrological context of the studied area at the catchment scale. Combining those results with geophysical measurements allows validating and imaging them at a smaller scale, with more integrative techniques. Hydrogeophysical measurements are focused on only one cave system of the LKS, at the Rochefort site (∼40 ha), taking benefit of the Rochefort Cave Laboratory (RCL) infrastructures. In this study, a microgravimetric monitoring and an Electrical Resistivity Tomography (ERT) monitoring are involved. The microgravimetric monitoring consists in a superconducting gravimeter continuously measuring gravity changes at the surface of the RCL and an additional relative gravimeter installed in the underlying cave located 35 meters below the surface. While gravimeters are sensible to changes that occur in both the vadose zone and the saturated zone of the whole cave system, combining their recorded signals allows enhancing vadose zone’s gravity changes. Finally, the surface ERT monitoring provide valuable information at the (sub)-meter scale on the hydrological processes that occur in the vadose zone. Seasonal water variations and preferential flow path are observed. This helps separating the hydrological signature of the vadose zone from that of the saturated zone. [less ▲]

Detailed reference viewed: 62 (10 UL)
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Peer Reviewed
See detailShort-term Time Series Forecasting with Regression Automata
Lin, Qin; Hammerschmidt, Christian UL; Pellegrino, Gaetano et al

Poster (2016)

We present regression automata (RA), which are novel type syntactic models for time series forecasting. Building on top of conventional state-merging algorithms for identifying automata, RA use numeric ... [more ▼]

We present regression automata (RA), which are novel type syntactic models for time series forecasting. Building on top of conventional state-merging algorithms for identifying automata, RA use numeric data in addition to symbolic values and make predictions based on this data in a regression fashion. We apply our model to the problem of hourly wind speed and wind power forecasting. Our results show that RA outperform other state-of-the-art approaches for predicting both wind speed and power generation. In both cases, short-term predictions are used for resource allocation and infrastructure load balancing. For those critical tasks, the ability to inspect and interpret the generative model RA provide is an additional benefit. [less ▲]

Detailed reference viewed: 25 (3 UL)
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See detailAssessment of BLT Tide Gauge Benchmark Monitoring (TIGA) repro2 Solutions
Hunegnaw, Addisu UL; Teferle, Felix Norman UL

Poster (2015, December 17)

In 2013 the International GNSS Service (IGS) Tide Gauge Benchmark Monitoring (TIGA) Working Group (WG) started their reprocessing campaign, which proposes to re-analyze all relevant Global Positioning ... [more ▼]

In 2013 the International GNSS Service (IGS) Tide Gauge Benchmark Monitoring (TIGA) Working Group (WG) started their reprocessing campaign, which proposes to re-analyze all relevant Global Positioning System (GPS) observations from 1994 to 2013. This re-processed dataset will provide high quality estimates of land motions, enabling regional and global high-precision geophysical/geodetic studies. Several of the individual TIGA Analysis Centres (TACs) have completed processing the full history of GPS observations recorded by the IGS global network, as well as, many other GPS stations at or close to tide gauges, which are available from the TIGA data centre at the University of La Rochelle (www.sonel.org). Following the recent improvements in processing models and strategies, this is the first complete reprocessing attempt by the BLT TIGA Analysis centre to provide homogeneous position time series. We report the quality of the multi-year daily solutions from the consortium of the British Isles continuous GNSS Facility (BIGF) and the University of Luxembourg TIGA Analysis Centres (BLT) based on the Bernese GNSS Software Version 5.2 using a double difference (DD) network processing strategy. [less ▲]

Detailed reference viewed: 51 (9 UL)
Peer Reviewed
See detailMetacognitive approach of decision processes implied in time perception
Lamotte, Mathilde UL; Droit-Volet, Sylvie; Izaute, Marie

Poster (2015, November)

Detailed reference viewed: 16 (0 UL)
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See detailSignal Obstructions at GNSS Stations: Benefits From Multi-GNSS Observations
Abraha, Kibrom Ebuy UL; Teferle, Felix Norman UL; Hunegnaw, Addisu UL et al

Poster (2015, October 27)

The current accuracy of IGS products, few centimeter level, requires amongst other things that the location for GNSS antennas are nearly optimal for GNSS observations. This includes a low multipath ... [more ▼]

The current accuracy of IGS products, few centimeter level, requires amongst other things that the location for GNSS antennas are nearly optimal for GNSS observations. This includes a low multipath environment and little to no signal obstructions. However, this is not guaranteed for every station especially in urban areas and mountainous regions. As some applications such as GNSS for sea level studies or to monitor landslides require GNSS antennas to be installed at a specific site, it is clear that the environment might not be favourable for GNSS observations. In this study, we investigate the effect of signal obstructions on station positions, specifically the height component, based on simulated obstruction scenarios using a modified Bernese GNSS Software version 5.2 (BSW52). The behaviours of different obstruction scenarios and the impact of multi-GNSS (GPS+GLONASS for now) observations for both clear and obstructed stations are discussed. [less ▲]

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See detailPraxis- a Kontaktdag
Böwen, Petra UL; Dujardin, Céline UL; Romberg, Kathrin UL

Poster (2015, October 22)

Wir bieten Studierenden und Arbeitgebern die Möglichkeit, persönlichen Kontakt herzustellen und/oder zu pflegen. Auch Studieninteressierte und die interessierte Öffentlichkeit können „Wissenschaft und ... [more ▼]

Wir bieten Studierenden und Arbeitgebern die Möglichkeit, persönlichen Kontakt herzustellen und/oder zu pflegen. Auch Studieninteressierte und die interessierte Öffentlichkeit können „Wissenschaft und Praxis“ hautnah erleben. Im Mittelpunkt steht der persönliche Kontakt. Sie als Praxiseinrichtungen bekommen die Möglichkeit, sich und Ihre Arbeit zu präsentieren. Sie können Kontakte mit potentiellen Praktikanten, Honorarkräften und evtl. zukünftigen Berufseinsteigern herstellen und auch ehrenamtliche Mitarbeiter gewinnen. Sie als Studierende können Kontakte knüpfen für ein konkretes Praktikum, zum Kennenlernen eines bestimmten Praxisfeldes oder zur Kontaktaufnahme mit einem potentiellen Arbeitgeber. [less ▲]

Detailed reference viewed: 59 (7 UL)
Peer Reviewed
See detailMath anxiety is predicted by the strength of number-space associations, over and beyond arithmetic ability and WM
Georges, Carrie UL; Hoffmann, Danielle UL; Schiltz, Christine UL

Poster (2015, October)

Math skills are undeniably important in everyday life. Math anxiety can, however, threaten their optimal development. Given that a fifth of the population experiences high math anxiety, it is important to ... [more ▼]

Math skills are undeniably important in everyday life. Math anxiety can, however, threaten their optimal development. Given that a fifth of the population experiences high math anxiety, it is important to identify its origins in order to improve mathematical learning. Research on math anxiety typically focusses on the effects of math ability, WM, and spatial performance. Recent evidence, however, suggests that it also depends on basic numerical processes, with high math anxious individuals featuring less precise numerical representations, as indexed by stronger distance effects. Another marker for the nature of numerical representations is the SNARC effect, alluding to their spatial organization. Although number-space associations depend on WM, spatial performance and arithmetic ability - all related to math anxiety - their relationship with the latter has never been tested. We thus determined whether math anxiety is related to the strength of number-space associations. All participants (n=60, 28 female) completed the r-MARS, the parity judgment, an arithmetic, and visuospatial WM task. We replicated previous findings on the negative relationships between math anxiety and arithmetic ability (r=-0.3, p=0.02), and WM (r=-0.29, p=0.03). But most importantly, we found a significant negative correlation between the SNARC effect and math anxiety (slope=-11.42, r=-0.43, p<0.001), with high math anxious individuals featuring greater interference of the irrelevant magnitude-associated spatial code. Interestingly, number-space associations were the only significant predictor of math anxiety in a multiple regression analysis. Our findings thus provide further evidence for the association between numerical representations and math anxiety, over and beyond arithmetic ability and WM. [less ▲]

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