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See detailSchulische Kompetenzen von Erstklässlern und ihre Entwicklung nach zwei Jahren.
Hoffmann, Danielle UL; Hornung, Caroline; Gamo, Sylvie UL et al

Poster (2018, November 08)

Jedes Jahr werden in den luxemburgischen Schulen die ÉpStan (Épreuves Standardisées) durchgeführt. Hierbei handelt es sich um nationale Schulleistungstests, welche Kompetenzen im Bereich der Mathematik ... [more ▼]

Jedes Jahr werden in den luxemburgischen Schulen die ÉpStan (Épreuves Standardisées) durchgeführt. Hierbei handelt es sich um nationale Schulleistungstests, welche Kompetenzen im Bereich der Mathematik und den Schulsprachen (Luxemburgisch, Deutsch und Französisch) auf standardisierte Art messen. Der vorliegende Beitrag ist sowohl eine Bestandsaufnahme der Schülerschaft zu Beginn des formalen Bildungswegs als auch ein Bericht ihrer Evolution über zwei Jahre im luxemburgischen Schulsystem. Hierzu haben wir die Daten aus drei Erhebungen (2014, 2015, 2016) der ÉpStan analysiert. Zum einen zeigen wir, anhand von Daten aus drei verschiedenen Kohorten, welche schulischen Kompetenzen Erstklässler (Zyklus 2.1) am Anfang ihrer Schullaufbahn aufweisen. Zudem hatten wir die Möglichkeit die Schüler und Schülerinnen der ersten Erhebung (2014) zwei Jahre später im Zyklus 3.1 nochmals zu testen und somit ihren Entwicklungsverlauf über zwei Jahre im luxemburgischen Bildungssystem zu dokumentieren. Diese ersten längsschnittlichen Daten zeigen, dass die Mehrheit der Schülerinnen und Schüler zu Beginn des Zyklus 2.1 das Niveau Avancé in den drei überprüften Kernkompetenzen („Luxemburgisch-Hörverstehen“, „Vorläuferfertigkeiten der Schriftsprache“ und „Mathematik“) erreicht. Somit stellen wir fest, dass die für den ersten Lernzyklus festgehaltenen Bildungsstandards erfüllt sind. Zwei Jahre später fällt die Verteilung der Schülerinnen und Schüler auf die verschiedenen Kompetenzränge negativer aus als im Zyklus 2.1. Im Zyklus 3.1 haben vergleichsweise mehr Kinder das Niveau Socle in allen drei Kernkompetenzen („Deutsch-Hörverstehen“, „Deutsch-Leseverstehen“ und „Mathematik“) noch nicht erreicht. Unsere Befunde zeigen außerdem, dass verschiedene außerschulische Faktoren (wie z. B. sozioökonomische Situation, Sprachhintergrund) bereits sehr früh im Verlauf der Schullaufbahn einen äußerst starken Einfluss auf die Testergebnisse haben und sich dieser Einfluss über die Jahre hinweg verstärkt. Abschließend präsentieren und diskutieren wir verschiedene Erklärungsansätze für diesen beobachteten Schereneffekt. [less ▲]

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See detailDEMO: An Effective Android Code Coverage Tool
Pilgun, Aleksandr UL; Gadyatskaya, Olga UL; Dashevskyi, Stanislav UL et al

Poster (2018, October 15)

The deluge of Android apps from third-party developers calls for sophisticated security testing and analysis techniques to inspect suspicious apps without accessing their source code. Code coverage is an ... [more ▼]

The deluge of Android apps from third-party developers calls for sophisticated security testing and analysis techniques to inspect suspicious apps without accessing their source code. Code coverage is an important metric used in these techniques to evaluate their effectiveness, and even as a fitness function to help achieving better results in evolutionary and fuzzy approaches. Yet, so far there are no reliable tools for measuring fine-grained bytecode coverage of Android apps. In this work we present ACVTool that instruments Android apps and measures the smali code coverage at the level of classes, methods, and instructions. Tool repository: https://github.com/pilgun/acvtool [less ▲]

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See detailFacilitating Privacy-preserving Recommendation-as-a-Service with Machine Learning
Wang, Jun UL; Arriaga, Afonso; Tang, Qiang et al

Poster (2018, October)

Machine-Learning-as-a-Service has become increasingly popular, with Recommendation-as-a-Service as one of the representative examples. In such services, providing privacy protection for users is an ... [more ▼]

Machine-Learning-as-a-Service has become increasingly popular, with Recommendation-as-a-Service as one of the representative examples. In such services, providing privacy protection for users is an important topic. Reviewing privacy-preserving solutions which were proposed in the past decade, privacy and machine learning are often seen as two competing goals at stake. Though improving cryptographic primitives (e.g., secure multi-party computation (SMC) or homomorphic encryption (HE)) or devising sophisticated secure protocols has made a remarkable achievement, but in conjunction with state-of-the-art recommender systems often yields far-from-practical solutions. We tackle this problem from the direction of machine learning. We aim to design crypto-friendly recommendation algorithms, thus to obtain efficient solutions by directly using existing cryptographic tools. In particular, we propose an HE-friendly recommender system, refer to as CryptoRec, which (1) decouples user features from latent feature space, avoiding training the recommendation model on encrypted data; (2) only relies on addition and multiplication operations, making the model straightforwardly compatible with HE schemes. The properties turn recommendation-computations into a simple matrix-multiplication operation. To further improve efficiency, we introduce a sparse-quantization-reuse method which reduces the recommendation-computation time by $9\times$ (compared to using CryptoRec directly), without compromising the accuracy. We demonstrate the efficiency and accuracy of CryptoRec on three real-world datasets. CryptoRec allows a server to estimate a user's preferences on thousands of items within a few seconds on a single PC, with the user's data homomorphically encrypted, while its prediction accuracy is still competitive with state-of-the-art recommender systems computing over clear data. Our solution enables Recommendation-as-a-Service on large datasets in a nearly real-time (seconds) level. [less ▲]

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See detailThe Influence of Code Coverage Metrics on Automated Testing Efficiency in Android
Dashevskyi, Stanislav UL; Gadyatskaya, Olga UL; Pilgun, Aleksandr UL et al

Poster (2018, October)

Code coverage is an important metric that is used by automated Android testing and security analysis tools to guide the exploration of applications and to assess efficacy. Yet, there are many different ... [more ▼]

Code coverage is an important metric that is used by automated Android testing and security analysis tools to guide the exploration of applications and to assess efficacy. Yet, there are many different variants of this metric and there is no agreement within the Android community on which are the best to work with. In this paper, we report on our preliminary study using the state-of-the-art automated test design tool Sapienz. Our results suggest a viable hypothesis that combining different granularities of code coverage metrics can be beneficial for achieving better results in automated testing of Android applications. [less ▲]

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See detailThe Price of Privacy in Collaborative Learning
Pejo, Balazs UL; Tang, Qiang UL; Gergely, Biczok

Poster (2018, October)

Machine learning algorithms have reached mainstream status and are widely deployed in many applications. The accuracy of such algorithms depends significantly on the size of the underlying training ... [more ▼]

Machine learning algorithms have reached mainstream status and are widely deployed in many applications. The accuracy of such algorithms depends significantly on the size of the underlying training dataset; in reality a small or medium sized organization often does not have enough data to train a reasonably accurate model. For such organizations, a realistic solution is to train machine learning models based on a joint dataset (which is a union of the individual ones). Unfortunately, privacy concerns prevent them from straightforwardly doing so. While a number of privacy-preserving solutions exist for collaborating organizations to securely aggregate the parameters in the process of training the models, we are not aware of any work that provides a rational framework for the participants to precisely balance the privacy loss and accuracy gain in their collaboration. In this paper, we model the collaborative training process as a two-player game where each player aims to achieve higher accuracy while preserving the privacy of its own dataset. We introduce the notion of Price of Privacy, a novel approach for measuring the impact of privacy protection on the accuracy in the proposed framework. Furthermore, we develop a game-theoretical model for different player types, and then either find or prove the existence of a Nash Equilibrium with regard to the strength of privacy protection for each player. [less ▲]

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See detailVerlet buffer for broad phase interaction detection in Discrete Element Method
Mainassara Chekaraou, Abdoul Wahid UL; Rousset, Alban UL; Besseron, Xavier UL et al

Poster (2018, September 24)

The Extended Discrete Element Method (XDEM) is a novel and innovative numerical simulation technique that extends the dynamics of granular materials or particles as described through the classical ... [more ▼]

The Extended Discrete Element Method (XDEM) is a novel and innovative numerical simulation technique that extends the dynamics of granular materials or particles as described through the classical discrete element method (DEM) by additional properties such as the thermodynamic state, stress/strain for each particle. Such DEM simulations used by industries to set up their experimental processes are complexes and heavy in computation time. Therefore, simulations have to be precise, efficient and fast in order to be able to process hundreds of millions of particles. To tackle this issue, such DEM simulations are usually parallelized with MPI. One of the most expensive computation parts of a DEM simulation is the collision detection of particles. It is classically divided into two steps: the broad phase and the narrow phase. The broad phase uses simplified bounding volumes to perform an approximated but fast collision detection. It returns a list of particle pairs that could interact. The narrow phase is applied to the result of the broad phase and returns the exact list of colliding particles. The goal of this research is to apply a Verlet buffer method to (X)DEM simulations regardless of which broad phase algorithm is used. We rely on the fact that such DEM simulations are temporal coherent: the neighborhood only changes slightly from the last time-step to the current time-step. We use the Verlet buffer method to extend the list of pairs returned by the broad phase by stretching the particles bounding volume with an extension range. This allows re-using the result of the broad phase for several time-steps before an update is required once again and thereby its reduce the number of times the broad phase is executed. We have implemented a condition based on particles displacements to ensure the validity of the broad phase: a new one is executed to update the list of colliding particles only when necessary. This guarantees identical results because approximations introduced in the broad phase by our approach are corrected in the narrow phase which is executed at every time-steps anyway. We perform an extensive study to evaluate the influence of the Verlet extension range on the performance of the execution in terms of computation time and memory consumption. We consider different test-cases, partitioners (ORB, Zoltan, METIS, SCOTCH, ...), broad phase algorithms (Link cell, Sweep and prune, ...) and grid configurations (fine, coarse), sequential and parallel (up to 280 cores). While a larger Verlet buffer increases the cost of the broad phase and narrow phase, it also allows skipping a significant number of broad phase execution (> 99 \%). As a consequence, our first results show that this approach can speeds up the total .execution time up to a factor of 5 for sequential executions, and up to a factor of 3 parallel executions on 280 cores while maintaining a reasonable memory consumption. [less ▲]

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See detailAutogenous Laser welding of copper to aluminium
Mathivanan, Karthik UL; Plapper, Peter UL

Poster (2018, September 13)

This work investigates laser joining of copper sheets to aluminium in overlap configuration. Dissimilar Cu-Al connections are widely used in the electrical and electronics applications e.g. battery and ... [more ▼]

This work investigates laser joining of copper sheets to aluminium in overlap configuration. Dissimilar Cu-Al connections are widely used in the electrical and electronics applications e.g. battery and solar panels.Joining these materials is a very critical assembly process. The laser welding from the aluminium surface to copper (Al-Cu) is well described in the literature .But there is no data concerning the laser seam welding from the copper side to join with aluminium i.e Cu-Al.The selection of aluminium surface to irradiate is mainly because of poor absorption of copper to laser in IR region.But high intensities of about 100 MW/cm2 allow for initial vaporization of copper surface.Once the keyhole is generated, absorption of laser light is improved.Thereby high power lasers allow for successful penetration of copper surface to produce a joint with aluminium. The main objective is to investigate the approach of dissimilar laser welding starting from the copper surface to aluminium.The effect of process parameters on the shear force, microstructure and weld pool dimensions are studied.An experimental design is realized to see the effect of laser irradiation of copper surface (Cu-Al) in contrast to aluminium surface(Al-Cu). The selection of aluminium or copper surface is mainly dependent on the laser power.With the high power disk laser the possibility of joining from the copper side was evident and results of joining copper to aluminium and aluminium to copper are comparable.Therefore welding from a highly reflective surface to achive a comparable shear strength is demonstrated. [less ▲]

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See detailLaser micro-welding of wire to flat geometry for dissimilar materials in an electromechanical application
Amne Elahi, Mahdi UL; Plapper, Peter UL

Poster (2018, September 11)

In the presented study, the laser welding of wire to flat geometry for miniature electromechanical hybrid components has been investigated. Laser welding offers variety of advantages compared to the ... [more ▼]

In the presented study, the laser welding of wire to flat geometry for miniature electromechanical hybrid components has been investigated. Laser welding offers variety of advantages compared to the current joining processes for this application however, considering the geometry of parts to be welded also mechanical properties requirement, an accurate spatial modulation of laser beam should be implemented to achieve a sound joint. Tensile shear test and optical microscopy were employed to represent the mechanical properties and melt pool geometry of the joint. All welds were done by power modulation of the laser beam to better control the energy input at several feed rates and three different beam trajectories. Results show that the shear load of the joint can be controlled by feed rate and the trajectory of the laser beam. The material combination of the study (Nickel and CuSn6), represents solubility in solid state therefore, by defining a proper spatial modulation of the laser beam a joint stronger than base wire metal is achievable. Figure 1 represents schematics of weld components. [less ▲]

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See detailKnowledge Discovery Approach from Blockchain, Crypto-currencies, and Financial Stock Exchanges
Lagraa, Sofiane UL; Charlier, Jérémy Henri J. UL; State, Radu UL

Poster (2018, August 20)

Last few years have witnessed a steady growth in interest on crypto-currencies and blockchains. They are receiving considerable interest from industry and the research community, the most popular one ... [more ▼]

Last few years have witnessed a steady growth in interest on crypto-currencies and blockchains. They are receiving considerable interest from industry and the research community, the most popular one being Bitcoin. However, these crypto-currencies are so far relatively poorly analyzed and investigated. Recently, many solutions, mostly based on ad-hoc engineered solutions, are being developed to discover relevant analysis from crypto-currencies, but are not sufficient to understand behind crypto-currencies. In this paper, we provide a deep analysis of crypto-currencies by proposing a new knowledge discovery approach for each crypto-currency, across crypto-currencies, blockchains, and financial stocks. The novel approach is based on a conjoint use of data mining algorithms on imbalanced time series. It automatically reports co-variation dependency patterns of the time series. The experiments on the public crypto-currencies and financial stocks markets data also demonstrate the usefulness of the approach by discovering the different relationships across multiple time series sources and insights correlations behind crypto-currencies. [less ▲]

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See detailInfluence of pubic symphysis stiffness on pelvis stress distribution during single leg stance
Ricci, Pierre-Louis UL; Maas, Stefan UL; Gerich, Torsten et al

Poster (2018, July 09)

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See detailAcculturation as a success story: Theoretical elaborations, lay perceptions and empirical evidence for “successful” migration in the multicultural context of Luxembourg
Albert, Isabelle UL; Barros Coimbra, Stephanie UL

Poster (2018, July 04)

Acculturation research has for a long time concentrated on problematic issues related to migration, often taking a deficit approach. Only recently have researchers shifted their focus toward factors that ... [more ▼]

Acculturation research has for a long time concentrated on problematic issues related to migration, often taking a deficit approach. Only recently have researchers shifted their focus toward factors that might be linked to positive outcomes of migration and integration. The present paper will deal with the question of how individuals from migrant and non-migrant families might profit from multiculturalism and cultural diversity in a resource-oriented perspective. After a theoretical elaboration on how “successful” migration could be defined and by which indicators it could be measured, we will focus on lay perceptions of this concept drawing on qualitative interviews from the FNR-funded IRMA study (“Intergenerational Relations in the light of Migration and Ageing”). More precisely, a number of altogether n = 20 Portuguese immigrant and Luxembourgish dyads of one parent and one adult child each discussed about their experiences and views on migration and the multicultural context of Luxembourg. Finally, we will identify predictors of subjective well-being in a quantitative sample of n = 73 Portuguese immigrant families (mostly one adult child together with both parents), taking into account satisfaction in different life domains as well as social and temporal comparison processes. Analyses show that for first generation immigrants as well as for their children social downward comparisons with Luxembourgish and Portuguese peers living in the host country were beneficial for their subjective well-being, whereas comparisons with Portuguese still living in Portugal and temporal comparisons were less important. The discussion will propose an integrative model for the study of migration taking into account participants’ generation status and their migration history. [less ▲]

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See detailBlock Circulant Decomposition of Cross-Correlation Matrix for Transmit MIMO Beamforming
Hammes, Christian UL; Shankar, Bhavani UL; Ottersten, Björn UL

Poster (2018, July)

This paper deals with the design of transmit probing signal under the trade-off between good target discrimination (low cross-correlation beam pattern) and beam pattern design (desired auto-correlation ... [more ▼]

This paper deals with the design of transmit probing signal under the trade-off between good target discrimination (low cross-correlation beam pattern) and beam pattern design (desired auto-correlation beam pattern) in a Multiple-Input- Multiple-Output (MIMO) radar configuration. The quartic optimization problem, with a finite alphabet constraint on the probing signal and using Quadrature Phase Shift Keying (QPSK) in a multiplexed antenna system, is solved through a Fourier series approximation of the desired beam pattern by exploiting a block circulant property of the transmit signal matrix. The mean square error between an ideal and the proposed crosscorrelation beam pattern is -35 dB enhancing the attractiveness of the proposed approach. [less ▲]

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See detailAssessing creativity
Gubenko, Alla UL; Houssemand, Claude UL

Poster (2018, July)

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

Poster (2018, June 28)

Although numerical skills are essential in modern societies, 5- 7 % of the population suffer from mathematical learning disabilities. Due to the hierarchical nature of mathematical knowledge, screening ... [more ▼]

Although numerical skills are essential in modern societies, 5- 7 % of the population suffer from mathematical learning disabilities. Due to the hierarchical nature of mathematical knowledge, screening during the earliest stages of learning is essential to intervene efficiently. While different screening tools exist, they rely on verbal instructions and task content, hampering their usefulness in linguistically heterogeneous young school populations. We developed a computerized task that requires subjects to encode both auditory and visual numerical information to successfully respond to the task’s demands. For task instruction, participants were presented a video showing a person correctly solving three easy items of the task, before moving on to a practice session of three different items. If any item was solved incorrectly, the entire practice session was repeated for the participant. We administered the task to a sample of first grade students and collected participant’s performance in standardized addition, subtraction and number comparison (1 & 2-digit) tasks. A multivariate analysis with practice repetition as between-subject factor on the four standardized control measures revealed that participants that repeated the practice session scored significantly lower in three out of four dependent measures. These results suggest that the immediate understanding (i.e. practice items solved correctly on the first try) of our task, requiring deductive reasoning and an abstract, format-independent representation of quantity, is able to differentiate between high and low performers on standardized measures of basic math competence non-verbally at an early stage of learning. Implications and limitations will be discussed. [less ▲]

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See detailAutomatic discrimination of digits and letters in first graders and adults: an EEG Fast Periodic Visual Stimulation study.
Lochy, Aliette UL; Schiltz, Christine UL

Poster (2018, June)

Both letters and digits are arbitrary visual shapes that are distinguished into categories only after cultural acquisition. The observation that digits are easier to identify than letters has been ... [more ▼]

Both letters and digits are arbitrary visual shapes that are distinguished into categories only after cultural acquisition. The observation that digits are easier to identify than letters has been repeatedly reported in the literature (Shubert, 2017). In the present study, we used a Fast Periodic Visual Stimulation approach with EEG recordings to assess the automatic discrimination of letters and digits from each other in 1st grade children (N=17) and in adults (N=18). Participants viewed 40 sec sequences (3 repetitions per condition) of frequent stimuli (letters or digits) at a fast periodic rate (adults: 10Hz, children: 6Hz), in which rare stimuli (the other category of alphanumeric symbols) were periodically inserted (every five items, e.g., adults: at 2Hz, children: at 1.2Hz). Results showed discrimination responses in both groups in posterior occipito-temporal regions with clear changes in lateralization patterns. In children, stimuli contained only single elements. Responses were right-lateralized for digits among letters, and revealed a trend for left-lateralization for letters among digits. In adults, when stimuli contained only 1 character, both letters and digits gave rise to responses in the RH. However, when strings of characters were presented, then letters were discriminated from digits in the LH. These findings show a developmental pattern where single elements in children seem to be processed like strings of elements in adults. [less ▲]

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See detailIdentification patterns and subjective well-being in native and migrant emerging adults: The mediating role of self-efficacy
Stogianni, Maria UL; Murdock, Elke UL

Poster (2018, May 18)

Background: Luxembourg is one of the most diverse countries in Europe with a foreign population percentage of 47%. National identification processes become complex for young adults growing up in this ... [more ▼]

Background: Luxembourg is one of the most diverse countries in Europe with a foreign population percentage of 47%. National identification processes become complex for young adults growing up in this multicultural context with important implications for psychological outcomes. Research has shown that salience of national identification is heightened within this multicultural context (Murdock, Hirst, & Ferring, 2014) while higher levels of national identification are associated with life satisfaction and better health outcomes. Other findings suggest that intercultural contact can contribute to the development of a shared identity in highly diverse areas. The aim of this study was to investigate differences in identification patterns among native and non-native emerging adults and potential factors that mediate their impact on subjective well-being. As the native population is almost in the minority within its own country, we wanted to explore the relationships between well-being, ethnic, and transnational identification among this group. Methods: The sample included 260 young adults, ranging from 18 to 29 years old (M = 21.78, SD = 2.36). Participants were native citizens of Luxembourg and immigrants from different ethnic backgrounds. They completed standardized self-report questionnaires, including the Satisfaction with Life Scale and the General Self-Efficacy Scale. Identification with Luxembourg was assessed with the Multigroup Ethnic Identity Measure. Based on previous studies (van de Vijver et al, 2015), a 7-item scale was developed for the assessment of cosmopolitan/transnational identification, including items that assess beliefs about global citizenship and the level of contact with people from different ethnic groups. Results: All participants reported high levels of Luxembourgish and cosmopolitan identification with average scores M = 3.23 (SD = .79) and M = 4.15 (SD = .49) respectively. There were no significant differences for Luxembourgish identification and well-being between natives and non-natives but participants with migratory background scored significantly higher on the cosmopolitan identity scale. Luxembourgish and cosmopolitan identity correlated positively with self-efficacy in both groups and self-efficacy perceptions were positively related to well-being. To examine the direct and indirect relationships among these variables, we tested path mediation models with the two identity domains as predictors. The first model tested the mediating effect of self-efficacy on the relationship between identification patterns and well-being among native Luxembourgish citizens. The model showed a good fit χ²(1, N = 112) = .087, p = .768, RMSEA = .000, CFI = 1.00, indicating that ethnic identity was a significant predictor of self-efficacy perceptions which indeed mediated the effect of ethnic identification on well-being. Ethnic and transnational identification were not directly associated with the outcome variable. A second path model tested these relationships in the immigrant group χ²(1, N =145) = 2.452, p = .117, RMSEA = .100, CFI = .946. Neither identity component (Luxembourgish or cosmopolitan identity) was a significant predictor of subjective well-being but the findings suggest a mediating effect of self-efficacy on the relationship between transnational identification and well-being. Discussion: The present study contributes to the literature by exploring potential individual difference variables that affect the link between identification patterns and life satisfaction. [less ▲]

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See detailOn Standardised UAV Localisation and Tracking Systems in Smart Cities
Samir Labib, Nader UL; Brust, Matthias UL; Danoy, Grégoire UL et al

Poster (2018, May)

In the near future, more than two thirds of the world’s population is expected to be living in cities and hence, with the aim of being proactive and finding innovative and sustainable solutions ... [more ▼]

In the near future, more than two thirds of the world’s population is expected to be living in cities and hence, with the aim of being proactive and finding innovative and sustainable solutions, governments have made smart cities one of their priority areas of research. Smart cities are sustainable, inclusive and prosperous greener cities that foster enabling smart Information and Communication Technologies (smart ICT) like Internet-of-Things (IoT), cloud computing and big data to facilitate services such as mobility, governance, utility and energy management. As these services depend heavily on data collected by sensors, Unmanned Aerial Vehicles (UAVs) have quickly become one of the promising IoT devices for smart cities thanks to their mobility, agility and customizability of onboard sensors. UAVs found use in a wide array of applications expanding beyond military to more commercial ones, ranging from monitoring, surveillance, mapping to parcel delivery and more demanding applications that require UAVs to operate in heterogeneous swarms in a shared low-altitude airspace over populated cities. However, as the number of UAVs continues to grow and as their sensing, actuation, communication and control capabilities become increasingly sophisticated, UAV deployment in smart cities is faced with a set of fundamental challenges in their safe operation and management. These challenges emphasize the need for establishing globally-harmonised regulations and internationally-agreed-upon technical standards to govern the rapid technological advancements, as well as ensure a fair economy by encouraging market competition and lowering barriers to entry for newcomers. As various Standardisation Development Organisations (SDOs) recently recognised the need, importance and potential of such regulations, most have established dedicated working groups addressing UAVs. However, most current SDO committees focus on aspects such as vehicle categorisation, specifications and operational procedures, but one usually overlooked elementary topic is UAV localisation. Due to its importance and close relation to other technical subsystems, the lack of a resilient, scalable and efficient standardised UAV localisation and tracking system is one of the main obstructing barriers hindering the integration and interoperability of UAV swarms in smart cities and hence impeding the realisation of their vast application benefits. In this work, we focus on studying the fundamental technical requirements, specifications and functions of such UAV localisation and tracking system, and explore its relationship to and importance in 1) optimising path planning, flight scheduling and utilising shared airspace, 2) collision avoidance and conflict resolution in highly populated residential areas and 3) addressing privacy and data protection concerns that could arise from UAV monitoring and surveillance applications. Furthermore, for each of the three aspects, we analyse current SDOs efforts such as those put forth by EASA, EUCARE WG73 and ISO TC20/SC16 on UAV systems, ISO JTC1/SC41 on IoT and related technologies and ISO JTC1/SC27, EU Directive 95/46 EC and GDPR on security, privacy and data protection, in order to identify and prioritise future research questions in relation to UAV localisation, aiming to make a contribution towards narrowing the gap between research and existing technical standards by encouraging multimode standardisation. This research was conducted in collaboration with ILNAS - the Institut Luxembourgeois de la Normalisation, de l’Accréditation, de la Sécurité et qualité des produits et services (ILNAS) under the authority of the Minister of Economy, Luxembourg. [less ▲]

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See detailHow to threaten male gamers: The effects of stereotype threat on video game performance
Wagener, Gary L.; Melzer, André UL

Poster (2018, May)

A total of 70 participants (47.1% men) took part in a lab experiment that manipulated stereotype threat (i.e., the risk of confirming a negative stereotype about one’s group) between playing a video game ... [more ▼]

A total of 70 participants (47.1% men) took part in a lab experiment that manipulated stereotype threat (i.e., the risk of confirming a negative stereotype about one’s group) between playing a video game (Bejeweled 3). Participants performed generally worse after reading a fictitious article on gaming research that women would still play less and perform worse in games than men (ST condition). In contrast to males, however, female participants reported greater frustration from reading this article than their colleagues who read that women and men no longer differ in terms of playing frequency and performance skills (no ST condition). Interestingly, a reverse pattern of results was obtained for male participants, who reported a stronger negative effect of the article in the no ST condition on their ability to show their best gaming performance. Apparently, stereotype threat may affect video game performance both for women and men, but for different reasons. [less ▲]

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See detailTowards multiscale data fusion of high-resolution space borne and terrestrial datasets over Tristan da Cunha
Backes, Dietmar UL; Teferle, Felix Norman UL; Abraha, Kibrom Ebuy UL et al

Poster (2018, April 10)

Ever improving low cost, lightweight and easy to use sensing technologies are enabling the capture of rich 3D Datasets to support an unprecedented range of applications in Geosciences. Especially low-cost ... [more ▼]

Ever improving low cost, lightweight and easy to use sensing technologies are enabling the capture of rich 3D Datasets to support an unprecedented range of applications in Geosciences. Especially low-cost LiDAR systems as well as optical sensors, which can be deployed from terrestrial or low altitude aerial platforms, allow the collection of large datasets without detailed expert knowledge or training. Dense pointcloud derived from these technologies provide an invaluable source to fill the gap between highly precise and accurate terrestrial topographic surveys and large area Digital Surface Models (DSMs) derived from airborne and spaceborne sensors. However, the collection of reliable 3D pointclouds in remote and hazardous locations remains to be very difficult and costly. Establishing a reliable georeference, ensuring accuracy and data quality as well as merging such rich datasets with existing or space borne mapping provide additional challenges. The presented case study investigates the data quality and integration of a heterogeneous dataset collected over the remote island of Tristan da Cunha. High-resolution 3D pointclouds derived by TLS and drone Photogrammetry are merged with space borne imagery while preserving the accurate georeference provided by Ground Control derived from geodetic observations. The volcanic island of Tristan da Cunha located in the centre of the Southern Atlantic Ocean is one of the most remote and difficult to access locations on the planet. Its remote location, rough climatic conditions and consistent cloud coverage provides exceptional challenges for terrestrial, aerial as well as space borne data acquisition. Amongst many other scientific installations, the island also hosts a continuous GNSS station observation and monitoring facilities operated by the University of Luxembourg, which provided the opportunity to conduct a local terrestrial data acquisition campaign consistent with a terrestrial ground survey, Laserscanning and an image acquisition from a low-cost drone. The highly accurate Ground Control network, observed by GNSS and total station, provides a reliable georeference. Pointclouds were acquired around the area of the harbour using a Leica P20 terrestrial Laserscanner, as well as drone Photogrammetry based on images collected by a low-cost DJI Phantom3 drone. To produce a map of the complete island a comprehensive dataset of high-resolution space borne imagery based on the Digital Globe WorldView constellation was acquired which provided high resolution mapping information. The case study presents a cross-validation of terrestrial, low altitude airborne as well as spaceborne datasets in terms coregistration, absolute georeference, scale, resolution and overall data quality. Following the evaluation a practical approach to fuse this heterogeneous dataset is applied which aims to preserve overall data quality, local resolution and accurate georeference and avoid edge artefacts. The conclusions drawn from our preliminary results provide some good practice advice for similar projects. The final topographic dataset enables mapping and monitoring of local geohazards as, e.g. coastal erosion and recent landslides thus also supporting the local population. [less ▲]

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See detailVertical Land Movements and Sea Level Changes around South Georgia Island
Teferle, Felix Norman UL; Hunegnaw, Addisu UL; Abraha, Kibrom Ebuy UL et al

Poster (2018, April 09)

South Georgia Island in the Southern Atlantic Ocean is a key location for the seismic, geomagnetic and oceanic global monitoring networks. In its sub-Antarctic location, the island is largely covered by ... [more ▼]

South Georgia Island in the Southern Atlantic Ocean is a key location for the seismic, geomagnetic and oceanic global monitoring networks. In its sub-Antarctic location, the island is largely covered by mountain glaciers which have been reported to be retreating due to climatic change. Furthermore, during past glaciation periods the island and its shelf area have been ice covered as was revealed by scarring of the sub-oceanic topography. Together with ongoing tectonics along the North Scotia Ridge, these processes have the ability to produce significant uplift on local to regional scales, affecting the measurements of the tide gauge (GLOSS ID 187) at King Edward Point (KEP). Furthermore, with its mid-ocean location, the tide gauge is of particular interest to satellite altimetry calibrations over the Southern Atlantic and Southern Oceans. With the establishment of five GNSS stations on the islands during 2013 to 2015 and the scientific analysis of these data within the global network of stations of the International GNSS Service Tide Gauge Benchmark Monitoring (TIGA) working group, it has now become possible to study present-day vertical land movements of the region and their impacts on, for example, regional sea level. Furthermore, together with four precise levelling campaigns of the KEP benchmark network in 2013, 2014 and two in 2017, it has also been possible to investigate the very local character of the vertical motions near KEP, ie. the stability of the jetty upon which the tide gauge is mounted. In this study, we will present the still preliminary results from the GNSS and levelling measurements and will discuss their impact on the sea level record from the KEP tide gauge. Our measurements show that while South Georgia Island and the area around KEP are rising, the jetty and tide gauge are subsiding, leading to a disagreement in the observed sea level change from the tide gauge and satellite altimetry. In order to improve the agreement between these sea level measurements both local and regional vertical land movements need to be monitored. [less ▲]

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Peer Reviewed
See detailOvercoming language barriers in early mathematics instruction with “MaGrid” - a language-neutral training tool for multilingual school settings
Cornu, Véronique UL; Pazouki, Tahereh UL; Schiltz, Christine UL et al

Poster (2018, April 08)

Mathematical knowledge at the onset of formal schooling paves the way for children’s achievement in formal mathematics (e.g. Duncan et al., 2007; Watts et al., 2014). Hence, it is crucial to equip ... [more ▼]

Mathematical knowledge at the onset of formal schooling paves the way for children’s achievement in formal mathematics (e.g. Duncan et al., 2007; Watts et al., 2014). Hence, it is crucial to equip children with sound basic mathematical competencies by deploying effective teaching interventions during preschool years. However, multilingual school settings, such as Luxembourg (65% of the pupils are second language learners) pose a special challenge for instruction. Non-native pre-schoolers perform lower on early mathematics tests than their age-matched peers (Bonifacci et al., 2016; Kleemans et al., 2011). This gap is most likely due to missing out on learning opportunities, as a result of lower proficiency in the language of instruction. To provide equal access to early mathematics education for all children, we developed a language-neutral early mathematics training tool, the “MaGrid”-app. This innovative training tool has been evaluated, so far, in two studies in multilingual Luxembourg. In a first study, children from five classrooms (N = 68) used the tool to train visuo-spatial abilities, an important predictor of mathematical abilities (see e.g. Mix et al., 2016), over ten weeks (2x20min/week). At post-test, significant gains in the visuo-spatial domain were observed, compared to children from “teaching-as-usual” classrooms (N = 57). In a second study, we elaborated a comprehensive language-neutral early mathematics intervention, with “MaGrid” at its core. Findings from both training studies will be presented in detail and the importance of domain-specific versus domain-general precursors, as well as practical implications, will be discussed. [less ▲]

Detailed reference viewed: 130 (21 UL)
Peer Reviewed
See detailFourth-graders' competence beliefs in mathematics
Villanyi, Denise UL; Wollschläger, Rachel UL; Martin, Romain UL et al

Poster (2018, February 15)

Detailed reference viewed: 51 (12 UL)
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See detailUsing higher-order adjoints to accelerate the solution of UQ problems with random fields
Hale, Jack UL; Hauseux, Paul UL; Bordas, Stéphane UL

Poster (2018, January 08)

A powerful Monte Carlo variance reduction technique introduced in Cao and Zhang 2004 uses local derivatives to accelerate Monte Carlo estimation. This work aims to: develop a new derivative-driven ... [more ▼]

A powerful Monte Carlo variance reduction technique introduced in Cao and Zhang 2004 uses local derivatives to accelerate Monte Carlo estimation. This work aims to: develop a new derivative-driven estimator that works for SPDEs with uncertain data modelled as Gaussian random fields with Matérn covariance functions (infinite/high-dimensional problems) (Lindgren, Rue, and Lindström, 2011), use second-order derivative (Hessian) information for improved variance reduction over our approach in (Hauseux, Hale, and Bordas, 2017), demonstrate a software framework using FEniCS (Logg and Wells, 2010), dolfin-adjoint (Farrell et al., 2013) and PETSc (Balay et al., 2016) for automatic acceleration of MC estimation for a wide variety of PDEs on HPC architectures. [less ▲]

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Peer Reviewed
See detailPoster: Performance Evaluation of an Open-Source Audio-Video Bridging/Time-Sensitive Networking Testbed for Automotive Ethernet
Xu, Teng Andrea; Adamsky, Florian UL; Turcanu, Ion UL et al

Poster (2018)

Automotive Ethernet (AE) is becoming more and more relevant to the automotive industry due to its support of emerging in-car applications, which have high bandwidth demands and stringent requirements in ... [more ▼]

Automotive Ethernet (AE) is becoming more and more relevant to the automotive industry due to its support of emerging in-car applications, which have high bandwidth demands and stringent requirements in terms of latency and time synchronization. One of the standards under consideration for AE is IEEE 802.1 Audio Video Bridging (AVB)/Time Sensitive Networking (TSN) that provides deterministic data link layer and bounded latency to real-time traffic classes. So far, this protocol stack has only been evaluated using either simulations or proprietary and expensive platforms. In this paper, we design a real testbed system for AE using general-purpose single-board computers and conduct experiments to assess the real-time performance of an open-source AVB/TSN implementation. Our preliminary results show that even under heavy load, AVB/TSN can fulfil the latency requirements of AE while keeping a constant latency variation. [less ▲]

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Peer Reviewed
See detailSubjective Health Complaints in Adolescence - Validity of the HBSC Symptom Checklist in Luxembourg
Catunda, Carolina UL; Heinz, Andreas UL; Willems, Helmut UL

Poster (2018)

The HBSC Symptom Checklist (HBSC-SCL) consists on an eight-item scale developed for the Health Behaviour in School-aged Children survey to measure adolescent health complaints. Although it was developed ... [more ▼]

The HBSC Symptom Checklist (HBSC-SCL) consists on an eight-item scale developed for the Health Behaviour in School-aged Children survey to measure adolescent health complaints. Although it was developed based on a RASCH measurement analysis which proved that the items are indicators of a unidimensional latent trait, some studies suggests a two highly correlated dimensions. The objective of this study is to test the validity of the Luxembourgish version of the HBSC-SCL. Methods: The 2014 HBSC Luxembourg survey took place during the 2013/14 school year. A total of 590 classes following the national curriculum were randomly selected and 7 757 students aged from 11 to 18 years old responded to the questionnaire translated to both French and German distributed by their teachers. Findings: First, the Kaiser-Meyer-Olkin criterion and the Bartlett sphericity test indicated the use of a factor analysis (KMO=.88; p<.001). A Principal Component Analysis with Varimax Rotation (with the Eigenvalues over 1) and a scree plot test suggests a one factor matrix with a total variance explained of 47%. Discussion: Factor analysis support the existence of a single factor for the Luxemburgish population in accordance with the preliminary model developed. Literature have mixed results, with the possibility to compute one or two health complaints scores. More studies should confirm these findings but as the internal consistency possibly depends on the country studied, it is recommended this be systematically checked. [less ▲]

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Peer Reviewed
See detailA Reduced Order Kalman Filter for Computational Fluid-Dynamics Applications
Introini, Carolina; Cammi, Antonio; Lorenzi, Stefano et al

Poster (2018)

Detailed reference viewed: 34 (3 UL)
Peer Reviewed
See detailLa satisfaction de vie des adolescents au Luxembourg
Catunda, Carolina UL; Heinz, Andreas UL; Willems, Helmut UL

Poster (2018)

Dans l’objectif d’examiner la santé et le bien-être subjectif des jeunes en âge scolaire, l’enquête HBSC a été mis en place dans plusieurs pays de l’Europe. La satisfaction de vie est un concept central ... [more ▼]

Dans l’objectif d’examiner la santé et le bien-être subjectif des jeunes en âge scolaire, l’enquête HBSC a été mis en place dans plusieurs pays de l’Europe. La satisfaction de vie est un concept central dans l’évaluation du bien-être. Ainsi, l’objectif de la présente publication est de rendre compte de la satisfaction de vie des adolescents du Luxembourg, ainsi que d’identifier les tendances selon le sexe et l’âge. Méthode : Pour l’enquête HBSC 2014, la cohorte luxembourgeoise a été menée dans les écoles suivant le curriculum national pendant l’année scolaire 2013 / 2014. Au total, 7 757 élèves âgés de 11 à 18 ans, de 590 classes sélectionnées aléatoirement, ont participé à l’enquête. Leurs professeurs ont distribué un questionnaire en français / allemand composé, entre autres, de l’échelle de Cantril (1965) pour évaluer la satisfaction de vie et de questions sociodémographiques. Résultats : L'analyse des résultats montre une corrélation significative négative entre la satisfaction de vie et l’âge, les plus âgés ayant donc une moins bonne satisfaction de vie. Lorsque les analyses ont été faites séparément selon le sexe, ces tendances diffèrent. En ce que concerne les filles, les corrélations sont plus fortes. Par contre, pour les garçons, les liens sont moins importants. Dans les deux cas, les corrélations restent significatives. Des comparaisons de moyennes entre les sexes dans les différentes tranches d’âge indiquent aussi une satisfaction de vie plus élevé chez les garçons que les filles. Conclusion : Ces résultats suggèrent que la satisfaction de vie pendant l’adolescence diminue avec l’âge et que les garçons sont plus satisfaits de leur vie que les filles. Ces données corroborent les tendances retrouvés dans d’autres pays participants de l’enquête HBSC, ainsi que la littérature sur le sujet. Des analyses plus fines doivent être faites dans cette cohorte en prenant en considération ces différences. [less ▲]

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See detailFirst Vertical Land Movement Estimates on South Georgia Island: An Impact Study on Sea Level Change from Tide Gauge and Altimetry Measurements
Teferle, Felix Norman UL; Hunegnaw, Addisu UL; Abraha, Kibrom Ebuy UL et al

Poster (2017, December 11)

South Georgia Island in the Southern Atlantic Ocean has been a key location for the seismic, geomagnetic and oceanic global monitoring networks. However, no permanent geodetic monitoring station had been ... [more ▼]

South Georgia Island in the Southern Atlantic Ocean has been a key location for the seismic, geomagnetic and oceanic global monitoring networks. However, no permanent geodetic monitoring station had been established there despite the lack of observations from this region within, for example, the International GNSS Service (IGS) network of Global Navigation Satellite System (GNSS) stations. Then, in 2013 the King Edward Point (KEP) Geodetic Observatory was established with a focus on sea level studies and in support of general geoscience applications. Currently, this observatory located roughly half-way along the main island and along its northern coastline, consists of two GNSS stations (KEPA and KRSA) with local benchmark networks, allowing the height determinations from the GNSS antennas to be transferred to the KEP tide gauge (GLOSS ID 187) and forming a height reference within the International Terrestrial Reference Frame. In late 2014, three additional GNSS stations (SG01, SG02 and SG03) were established, all on small islands at the perimeter of the main island. Together the stations provide the best possible opportunity to study various geophysical processes in the region. With the GNSS-derived position time series partly reaching over 4.5 years in length, it has become possible to provide first estimates of vertical land movements for the island and KEP with its surrounding area. Together with four precise levelling campaigns of the benchmark network in 2013, 2014 and two in 2017, it has also been possible to investigate the very local character of the vertical motions, ie. the stability of the jetty upon which the tide gauge is mounted. Our measurements show that while South Georgia Island and the area around KEP are rising, the jetty and tide gauge are subsiding. In this study, we will present the preliminary results from the GNSS and levelling measurements and will discuss their impact on the sea level record from the KEP tide gauge which is ideally situated in a mid-ocean location for satellite altimetry calibration over the Southern Atlantic and Southern Oceans. [less ▲]

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Peer Reviewed
See detailPoster: Characterizing Driving Behaviors Through a Car Simulation Platform
Faye, Sébastien UL; Jafarnejad, Sasan UL; Costamagna, Juan UL et al

Poster (2017, November 27)

Human mobility has opened up to many themes in recent years. Human behavior and how a driver might react to certain situations, whether dangerous (e.g. an accident) or simply part of the evolution of new ... [more ▼]

Human mobility has opened up to many themes in recent years. Human behavior and how a driver might react to certain situations, whether dangerous (e.g. an accident) or simply part of the evolution of new technologies (e.g. autonomous driving), leaves many avenues to be explored. Although experiments have been deployed in real situations, it remains difficult to encounter the conditions that certain studies may require. For this reason, we have set up a driving simulator (comprising several modules) that is able to reproduce a realistic driving environment. Although, as the literature has already demonstrated, the conditions are often far from reality, simulation platforms are nonetheless capable of reproducing an incredibly large number of scenarios on the fly. In this poster, we explain how we conceived the simulator, as well as the system we developed for collecting metrics on both the driver and the simulation environment. In addition, we take advantage of this conference to publicly share a dataset consisting of 25 drivers performing the same road circuit on the "Project Cars" game. [less ▲]

Detailed reference viewed: 99 (15 UL)
See detailEarly life stress reduces neuropathic pain in adulthood -is alteration of spinal microglial reactivity critically involved?
Genty, Julien UL; Tetsi Nomigni, Milène UL; Anton, Fernand UL et al

Poster (2017, November 14)

Growing evidence underlines the association between early life adversity and persistent alterations of neural, endocrine and immune functions that may be accompanied by a host of disease patterns such as ... [more ▼]

Growing evidence underlines the association between early life adversity and persistent alterations of neural, endocrine and immune functions that may be accompanied by a host of disease patterns such as chronic pain in later life. Neuropathy is a debilitating condition presenting a substantial cooccurrence with stress related disorders. Despite the established overlapping of biochemical pathways involved in the etiology of these disorders, the intricacy of their mutual interdependence remains. In this context, immunocompetent cells are largely affected during chronic stress and are a key factor in the sensitization of nociceptive dorsal horn neurons. The goal of the present study was to investigate the impact of maternal separation (MS), a wellestablished model of early life stress in rodents, on chronic constriction injury (CCI)induced neuropathic pain and to reveal the relevance of spinal microglia activation and proinflammatory cytokine regulation. For this purpose 12 groups of rats were exposed to different combinations of stress condition, CCIinjury and pharmacological treatment. Noxious sensitivity was tested during baseline conditions as well as during subsequent neuropathic and pharmacological treatment conditions. Von Frey hair and the cold plate tests were used for the assessment of mechanical and cold hyperalgesia/allodynia. Amphotericin B, a substance known to activate monocytes and macrophages in the periphery and microglial cells in the CNS was administered to subgroups of animals. At the end of the protocol, rats were sacrificed to assess microglial activation using qPCR and immunohistochemistry. Our main finding was that maternal separation led to a reduction of CCIrelated pain hypersensitivity (thermal and mechanical hyperalgesia/allodynia). We concomitantly observed a downregulation of Iba 1, mRNA a marker of microglial cells, and of IL1β mRNA, a proinflammatory cytokine that may be released by microglia. According to preliminary results, Amphotericin B in turn seemed to enhance CCI related pain sensitivity, possibly via an activation of microglia. Our results show that MS may lead to a reduction of neuropathy relatedpain in adult age. Stress related dampening of spinal microglial reactivity may play a critical role in this context. [less ▲]

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See detailA Product Line of Software Engineering Project Courses
Guelfi, Nicolas UL; Capozucca, Alfredo UL; Ries, Benoît UL

Poster (2017, November 08)

Detailed reference viewed: 62 (7 UL)
Peer Reviewed
See detailReliable Machine Learning for Networking: Key Concerns and Approaches
Hammerschmidt, Christian UL; Garcia, Sebastian; Verwer, Sicco et al

Poster (2017, October)

Machine learning has become one of the go-to methods for solving problems in the field of networking. This development is driven by data availability in large-scale networks and the commodification of ... [more ▼]

Machine learning has become one of the go-to methods for solving problems in the field of networking. This development is driven by data availability in large-scale networks and the commodification of machine learning frameworks. While this makes it easier for researchers to implement and deploy machine learning solutions on networks quickly, there are a number of vital factors to account for when using machine learning as an approach to a problem in networking and translate testing performance to real networks deployments successfully. This paper, rather than presenting a particular technical result, discusses the necessary considerations to obtain good results when using machine learning to analyze network-related data. [less ▲]

Detailed reference viewed: 81 (2 UL)
Peer Reviewed
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 detailProject NUMTEST: Assessing basic number competence without language
Greisen, Max UL; Hornung, Caroline; Martin, Romain UL et al

Poster (2017, September 08)

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. Here we are showing results of the first two pilot studies 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 tasks has been tested with two samples of first grade children in Luxembourg’s fundamental schools, of which half completed the same tasks with traditional verbal instructions. Our results indicate that performance in the experimental group was similar or better than 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-pc use with young children will be discussed. [less ▲]

Detailed reference viewed: 64 (20 UL)
Peer Reviewed
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 ▲]

Detailed reference viewed: 317 (3 UL)
See detailEnergy and momentum distribution of fractional excitations in helical systems
Calzona, Alessio UL; Acciai, Matteo; Dolcetto, Giacomo UL et al

Poster (2017, September 05)

Detailed reference viewed: 24 (0 UL)
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 ▲]

Detailed reference viewed: 121 (15 UL)
See detailTransport properties as a tool to study universal features of quench-induced dynamics in 1D systems
Calzona, Alessio UL; Gambetta, Filippo Maria; Cavaliere, Fabio et al

Poster (2017, August 14)

Detailed reference viewed: 18 (2 UL)
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Peer Reviewed
See detailHuman in the Loop: Interactive Passive Automata Learning via Evidence-Driven State-Merging Algorithms
Hammerschmidt, Christian UL; State, Radu UL; Verwer, Sicco

Poster (2017, August)

We present an interactive version of an evidence-driven state-merging (EDSM) algorithm for learning variants of finite state automata. Learning these automata often amounts to recovering or reverse ... [more ▼]

We present an interactive version of an evidence-driven state-merging (EDSM) algorithm for learning variants of finite state automata. Learning these automata often amounts to recovering or reverse engineering the model generating the data despite noisy, incomplete, or imperfectly sampled data sources rather than optimizing a purely numeric target function. Domain expertise and human knowledge about the target domain can guide this process, and typically is captured in parameter settings. Often, domain expertise is subconscious and not expressed explicitly. Directly interacting with the learning algorithm makes it easier to utilize this knowledge effectively. [less ▲]

Detailed reference viewed: 34 (1 UL)
See detailEnergy and momentum distribution of fractional excitations in 1D counterpropagating systems
Calzona, Alessio UL; Acciai, Matteo; Dolcetto, Giacomo UL et al

Poster (2017, July 25)

Detailed reference viewed: 18 (1 UL)
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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 detailCharge pumping through a polaron quantum dot
Haughian, Patrick UL; Yap, Han Hoe; Walter, Stefan et al

Poster (2017, July)

Nanoelectromechanical systems exhibit a rich phenomenology due to the interaction of electronic and mechanical degrees of freedom. If this interaction is sufficiently strong, it leads to drastic ... [more ▼]

Nanoelectromechanical systems exhibit a rich phenomenology due to the interaction of electronic and mechanical degrees of freedom. If this interaction is sufficiently strong, it leads to drastic suppression of conductance ("Franck-Condon blockade''). We show that this blockade can be exponentially lifted by application of an AC voltage. Multi-parameter drive protocols generate a pump current which enjoys the same enhancement. [less ▲]

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See detailMapping Combinational Circuits to Homogenous Trellis-Constrained Codes
Franck, Christian UL

Poster (2017, July)

Detailed reference viewed: 110 (13 UL)
Peer Reviewed
See detailDeniability in Quantum Cryptography
Atashpendar, Arash UL; Roenne, Peter UL; Ostrev, Dimiter UL et al

Poster (2017, June 14)

This poster describes ongoing work on deniability in quantum cryptography, an area of research that remains almost entirely unexplored in the quantum information processing literature. Deniability is a ... [more ▼]

This poster describes ongoing work on deniability in quantum cryptography, an area of research that remains almost entirely unexplored in the quantum information processing literature. Deniability is a well-known and fundamental concept in classical cryptography and it can be defined as the ability for the sender of a message to deny the contents of a message or the very act of having participated in an exchange, e.g. having sent the said message. We discuss deniability in the context of quantum key exchange and address a particular problem, first discovered by Donald Beaver, where he claims that all QKD protocols are undeniable. The claim is that while we do get a one-time pad (OTP) using QKD, it does not provide the property of key equivocation as it is expected in the Shannon sense for a OTP. Intuitively, this difficulty lies in the quantum channel alone and it has to do with the fact that in QKD, while we generate entropy by expanding an initially short pre-shared key into an arbitrary longer secret key, we do so by exchanging information over a quantum as well as a classical channel, which could potentially leave a binding transcript of Alice's decisions to the final secret key. This is in contrast with the implicit assumption that Eve knows nothing about how two given parties have established their shared OTP in the first place. We discuss the importance of deniability in cryptography and its wide range of applications, along with cryptographic primitives other than key exchange where deniability might be a desired property. Finally, we present a series of fundamental open questions in this area of research and discuss quantum cryptographic primitives that lend themselves to devising deniable protocols. [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 detailProject NUMTEST: Assessing basic number competence without language
Greisen, Max UL; Hornung, Caroline UL; Martin, Romain UL et al

Poster (2017, May 31)

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. Here we are showing results of 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 tasks has been tested with two samples of first grade children in Luxembourg’s fundamental schools, of which half completed the same tasks with traditional verbal instructions. Our results indicate that performance in the experimental group was similar or better than 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-pc use with young children will be discussed. [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 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 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 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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Peer Reviewed
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 detailVisuo-spatial abilities are key for children’s verbal number skills
Cornu, Véronique UL; Martin, Romain UL; Hornung, Caroline UL

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 UL 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 ▲]

Detailed reference viewed: 93 (17 UL)
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Peer Reviewed
See detailAnalyzing the relation between commuting satisfaction and residential choices using discrete choice theory and structural equation modeling
Sprumont, François UL; Astegiano, Paola; Viti, Francesco UL

Poster (2017, January)

The concept of travelling satisfaction is gaining more and more interest in the transportation field. While increasing travellers’ satisfaction should be a goal of policy makers and practitioners, a drop ... [more ▼]

The concept of travelling satisfaction is gaining more and more interest in the transportation field. While increasing travellers’ satisfaction should be a goal of policy makers and practitioners, a drop in commuting satisfaction might lead to switch from one mode to another. Objective trip characteristics (time, cost, mode) as well as other elements such as mode attitude, lifestyle, etc. affect travel satisfaction rating. Despite an extensive literature on travel satisfaction determinants, often, the interaction between the studied determinants is overlooked. The main aim of this paper is to quantify the impact (both direct and indirect) of residential choices on the home-to-work stated travelling satisfaction. Methodologically, a Discrete Choice Theory approach (via the well-known concept of the utility Logsum) and a Partial Least Square Structural Equation Modelling (PLS-SEM) approach have been used and compared. Results of both modelling approaches show that the direct effect of residential choices on commuting satisfaction is negligible compared to individuals’ external factors such as trip characteristics. However, using the PLS-SEM approach, indirect effects of residential choices on commuting satisfaction can be quantified [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 detailComparison of Several RANS Modelling for the Pavia TRIGA Mark II Research Reactor
Introini, Carolina; Baroli, Davide UL; Peters, Bernhard UL

Poster (2017)

In this study, a detailed analysis of the turbulent regime within the core of the Pavia TRIGA Mark II reactor is perfomed by means of an in-depth comparison of the RAS (Reynolds-Averaged Simulation ... [more ▼]

In this study, a detailed analysis of the turbulent regime within the core of the Pavia TRIGA Mark II reactor is perfomed by means of an in-depth comparison of the RAS (Reynolds-Averaged Simulation) turbulence models implemented in OpenFOAM. Aim of this analysis is to give some important information with respect to the flow regime within the core. The performance of the various models is tested against a LES (Large Eddy Simulation) of the innermost channel. [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 ▲]

Detailed reference viewed: 108 (3 UL)