Closed Form Discrete Unimodular MIMO Waveform Design Using Block Circulant Decomposition

Poster (2019, April 22)

This paper deals with the waveform design under the constraint of discrete multiphase unimodular sequences. It relies on Block Circulant decomposition of the slow-time transmitted waveform. The presented ... [more ▼]

This paper deals with the waveform design under the constraint of discrete multiphase unimodular sequences. It relies on Block Circulant decomposition of the slow-time transmitted waveform. The presented closed-form solution is capable of designing orthogonal signals, such that the virtual MIMO paradigm is enabled leading to enhanced angular resolution. On the other hand, the proposed method is also capable of approximating any desired radiation pattern within the physical limits of the transmitted array size. Simulation results prove the effectiveness in terms computational complexity, orthogonal signal design and the transmit beam pattern design under constant modulus constraint. [less ▲]

Improved Monitoringand Tracking Hurricanes using GPS Atmospheric WaterVapour

Poster (2019, April 09)

Laser beam joining of copper to aluminum sheet

Poster (2019, April 04)

Dissimilar metal joining plays a very important role in the battery connections, especially copper and aluminum sheets. The existing literatures for laser research mostly focused on joining from the less ... [more ▼]

Dissimilar metal joining plays a very important role in the battery connections, especially copper and aluminum sheets. The existing literatures for laser research mostly focused on joining from the less reflective aluminum side to bond with copper. In the current research, we explore the joining process from copper side.Finally the optical emission of Cu-Al joint is presented with 394 nm peak as an indication to study the melting of Al. [less ▲]

The social stratification of student trajectories in German higher education

Poster (2019, March 22)

The Legendary of St Maximin Near Trier : Sources and Neighborhood Relationships (13th-16th Centuries): New Considered Investigations

Poster (2019, March 10)

Do the relative pattern of green space within cities impact carbon uptake? A European scale analysis

Poster (2019, February 07)

A Markov Chain Monte Carlo Approach for Estimating Daily Activity Patterns

Poster (2019, January)

Determining the purpose of trips brings is a fundamental information to evaluate travel demand during the day and to predict longer-term impacts on the population’s travel behavior. The concept of tours ... [more ▼]

Determining the purpose of trips brings is a fundamental information to evaluate travel demand during the day and to predict longer-term impacts on the population’s travel behavior. The concept of tours is the most suited to consider the value of a daily scheduling of individuals and travel interdependencies. However, the meticulous care required for both collecting data of high quality and interpret results of advanced demand models are frequently considered as major drawbacks. The objective of this study is to incorporate into a standard trip-based model some inherent concepts of activity-based models in order to enhance the representation of travel behavior. The main focus of this work is to infer, employing utility theory, the trip purpose of a population, at a zonal level. Making use of Markov Chain Monte Carlo, a set of parameters is estimated in order to retrieve tour-based primitives of the demand. The main advantage of this methodology is the low requirements in terms of data, as no individual information are used, and the good interpretation of the model. Estimated parameters of the priors set a utility-based probability function for departure time, which allows to have a dynamic overview of the demand. In order to account for the tour consistency of travel decisions, a duration constraint is added to the model. The proposed model is applied to the region of Luxembourg city and the results show the potential of the methodologies for dividing an observed demand based on the activity at destination. [less ▲]

Reduced perceptual bias in mindfulness? Evidence from a pain-cueing paradigm

Poster (2019)

A Multi-Objective Optimization Algorithm to Generate Unbiased Stimuli Sequences for Cognitive Tasks

Poster (2019)

Cognitive scientists want to ensure that particular cognitive tasks target particular cognitive functions that can be mapped to stable neural markers. Numerous cognitive tasks, like the n-back, involve ... [more ▼]

Cognitive scientists want to ensure that particular cognitive tasks target particular cognitive functions that can be mapped to stable neural markers. Numerous cognitive tasks, like the n-back, involve generating sequence of trials which satisfy certain statistical properties.The common approach to generate these sequences however lacks a theoretical framework and induces unintentional structure in the sequences which affects both behavioral performance and might bias the people’s cognitive strategies when completing a task. For example, people might exploit local properties in a random sequence in their decision making process. We argue that optimized experimental design requires cognitive tasks to be served by stimulus sequence generators that satisfy multiple constraints, both at the global and at the local structures of the sequence and that these sequence properties need to be systematically incorporated in the behavioral data analysis pipeline. We then develop a framework to reformulate the sequence generation process as a compositional soft constraint satisfaction problem and offer a multi-objective, genetic-algorithm-based method to generate controlled sequences under behavioral and neural constraints. This approach provides a systematic and coherent framework to handle stimulus sequences which in turn will impact the insights that can be gained from the behavioral and neural data collected on people performing cognitive tasks using those sequences. [less ▲]

Z2n Generalization of the Schwarz Voronov embedding

Poster (2019)

Tradition, Family Business and Beyond

Poster (2019)

That tradition plays a role in family business is a long-acknowledged but often self-evident notion in family business research. As a result, the explanatory potential of tradition is oriented towards its ... [more ▼]

That tradition plays a role in family business is a long-acknowledged but often self-evident notion in family business research. As a result, the explanatory potential of tradition is oriented towards its function as a resource for enabling organizational performance or its role in aiding stability and change within family business settings, has been overshadowed. Drawing from a reading of selected works in sociology, history and moral philosophy, this paper addresses this limitation by offering a theoretical reflection on the notion of tradition. These readings provide a way of departing from the common view of tradition as unitary, static and fixed towards a conceptualization that views tradition as both multi-layered and multi-faceted—constituting an unfolding process that is continuously being received and enacted in family firms. This theoretical paper contributes to the family business literature by strengthening the conceptual foundation of the notion of tradition by advocating tradition as a concept through which the past and future is immanent in the present. From this, a future agenda for research is outlined. [less ▲]

ÆGIS: Smart Shielding of Smart Contracts

Poster (2019)

In recent years, smart contracts have suffered major exploits, losing millions of dollars. Unlike traditional programs, smart contracts cannot be updated once deployed. Though various tools were pro ... [more ▼]

In recent years, smart contracts have suffered major exploits, losing millions of dollars. Unlike traditional programs, smart contracts cannot be updated once deployed. Though various tools were pro- posed to detect vulnerable smart contracts, they all fail to protect contracts that have already been deployed on the blockchain. More- over, they focus on vulnerabilities, but do not address scams (e.g., honeypots). In this work, we introduce ÆGIS, a tool that shields smart contracts and users on the blockchain from being exploited. To this end, ÆGIS reverts transactions in real-time based on pat- tern matching. These patterns encode the detection of malicious transactions that trigger exploits or scams. New patterns are voted upon and stored via a smart contract, thus leveraging the benefits of tamper-resistance and transparency provided by blockchain. By allowing its protection to be updated, the smart contract acts as a smart shield. [less ▲]

Optimisation de la prise en charge médicale des patients sortant de prison au Luxembourg

Poster (2019)

Le passage en prison peut être un gain de chance pour la santé de la population carcérale qui a généralement un faible accès au système de soins. L’élargissement de prison peut devenir une période de ... [more ▼]

Le passage en prison peut être un gain de chance pour la santé de la population carcérale qui a généralement un faible accès au système de soins. L’élargissement de prison peut devenir une période de vulnérabilité où ce gain potentiellement acquis s’annule si la transition vers la société civile n’est pas anticipée. L’objectif principal était l’identification et l’analyse des facteurs qui favorisent et s’opposent à une pratique de soins primaires chez les patients sortant du milieu carcéral au Luxembourg. L’objectif secondaire était l’élaboration de recommandations à l’égard des principaux résultats en s’appuyant sur une revue de la littérature. Méthodes : Une enquête qualitative à l’aide d’entretiens semi-dirigés a été menée auprès de médecins généralistes et de patients-détenus. Les questions des deux guides d’entretien étaient semblables afin que l’analyse permette une mise en miroir des résultats. Un recueil des caractéristiques sociodémographiques a également été effectué. A l’aide de la transcription des entretiens, une analyse de contenu thématique catégorielle de ces derniers a été réalisée au regard des objectifs. Sur base des verbatim, des items ont été formulés et regroupés en dimensions puis en thèmes. Résultats : Notre analyse a mis en lumière le manque de relais entre la prison et l’extérieur à chaque étape de la prise en charge médico-psycho-sociale du point de vue des soins et des aides proposées en prison jusqu’à l’élargissement. Des recommandations concernant des améliorations possibles ont pu être proposées, comme la création d’un réseau de médecins généralistes prenant le relais ainsi qu’une véritable coopération avec des organisations prenant en charge des toxicomanes. Conclusion : Des reformes concernant les soins en prison devraient être envisagées entre le système de l’élargissement, la création de relais socio-médicaux et des alternatives à l’incarcération, en analogie aux transitions clinics retrouvés aux États-Unis. [less ▲]

Suicide Prevention in Luxembourg: Using the HBSC Symptom Checklist as an Alternative Tool for Screening

Poster (2018, December 07)

Introduction: Suicide is one of the leading causes of death of young people and as such, screening for suicidal ideation is a major public health concern. However, there is fear that exposure to suicide ... [more ▼]

Introduction: Suicide is one of the leading causes of death of young people and as such, screening for suicidal ideation is a major public health concern. However, there is fear that exposure to suicide-related content would encourage suicide attempt. This false idea is a great barrier to effectively screen. Hence, the need for tools without suicide content. Purpose: The goal of this study is to present a short tool that could be helpful for suicide screening and prevention. Materials and Methods: This study is based on the 2014 HBSC Luxembourg survey. A total of 5595 students aged from 12 to 18 years old in secondary school responded to a questionnaire translated to both French and German. Among others, it included the HBSC Symptom Checklist, a scale developed to measure eight health complaints (headache, abdominal pain, backache, feeling low, irritability, feeling nervous, sleeping difficulties and dizziness), as well as 4 questions asked in a logical sequence concerning sadness, suicide ideation, suicide planning and suicide attempt. Results: Multivariate Logistic Regression analyses with 24 potential indicators showed the number of health complaints as the most predictive indicator for suicide attempt (OR=1.248; C.I.: 1.175-1.325). Following, a significant ROC curve (area under the curve of 0.76; sensitivity=0.68 and specificity=0.73) and Youden Index (0.41) indicates the optimum cut-off at three complaints, with a predictive value of 17%. An alternative cut off point at four (sensitivity=0.57 and specificity=0.82; Youden Index of 0.39) has a predictive value of 21%. Conclusion: The HBSC Symptom Checklist seems to be a good predictor as each additional health complaint increases the risk of suicide attempt by 25%. In addition, it could be an alternative to traditional suicide screening measures, as its sensitivity, specificity and predictive values are similar to measures more commonly used, such as the Columbia Suicide Screen or the Beck Depression Inventory. Further work should be invested to validate the HBSC Symptom Checklist as a screening tool for suicide prevention. [less ▲]

Schulische Kompetenzen von Erstklässlern und ihre Entwicklung nach zwei Jahren.

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 ▲]

Entwicklung eines Fragebogens zur Erfassung des emotionalen Selbstkonzepts von Jugendlichen

Poster (2018, November)

LE MOYEN ÂGE ENTRE FASCINATION ET EMANCIPATION. ÉTAT DES LIEUX ET NOUVELLES PERSPECTIVES AU LUXEMBURG

Poster (2018, November)

DEMO: An Effective Android Code Coverage Tool

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 ▲]

Combining PET imaging and blood metabolomics data to improve machine learning models for Parkinson’s disease diagnosis

Poster (2018, October 08)

Objective: To investigate whether the integration of PET imaging and metabolomics data can provide improved machine learning models for PD diagnosis. Background: The reliable diagnosis of PD can remain ... [more ▼]

Objective: To investigate whether the integration of PET imaging and metabolomics data can provide improved machine learning models for PD diagnosis. Background: The reliable diagnosis of PD can remain challenging, even at the motor stage. PET imaging can be used to confirm the clinical diagnosis. However, limitations in the robustness of predictive features extracted from the data and the costs associated with PET imaging restrict its application. Using blood metabolomics data as an additional information source may provide improved combined diagnostic models and/or an initial filter to decide on whether to apply PET imaging. Methods: Metabolomics profiling of blood plasma samples using gas chromatography coupled to mass spectrometry (GC­MS) was conducted in 60 IPD patients and 15 healthy controls. After pre-processing, these data were compared to neuroimaging data for subsets of the same individuals using FDOPA PET (44 patients and 14 controls) and FDG PET (51 patients and 15 controls). Machine learning models using linear support vector machines were trained on 50% of the data and evaluated on a 50% hold­out test set using Receiver Operating Characteristic (ROC) curves. Next, standardized FDOPA and FDG PET intensity measurements were combined with those from the metabolomics data to build and evaluate sample classification models in the same manner as for the individual datasets. Results: Both for the FDOPA and FDG PET data, the predictive performance given by the area under the ROC curve (AUC) was highest when combining imaging features with those from the metabolomics data (AUC for FDOPA + metabolomics: 0.98; AUC for FDG + metabolomics: 0.91). The performance was generally lower when using only the respective PET attributes (FDOPA: 0.94, FDG: 0.8) or only the metabolomics data (AUC: 0.66). [less ▲]

Quantitative Erfassung von Behinderung. Entwicklung eines praxisrelevanten Erhebungsinstruments.

Poster (2018, October)

Das PALUX-Projekt in Luxemburg: Forschungsdesign und erste Ergebnisse einer Pilotstudie

Poster (2018, October)

Facilitating Privacy-preserving Recommendation-as-a-Service with Machine Learning

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 ▲]

Why engage with Digital Source Criticism?

Poster (2018, September 26)

This poster illustrates the concept of the teaching platform Ranke.2 with lessons on Digital Source Criticism

Verlet buffer for broad phase interaction detection in Discrete Element Method

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 ▲]

Autogenous Laser welding of copper to aluminium

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 ▲]

A multi-omic view of invasive genetic elements and their linked prokaryotic population dynamics within a mixed microbial community

Poster (2018, September 11)

Differential association of symbolic and non-symbolic numerical abilities in children with and without MLD – Evidence from large scale assessment data

Poster (2018, September)

Conception of the E-CIR “Measuring and supporting students’ social participation”. The 2018 E-CIR Group

Poster (2018, September)

The relation between visuospatial abilities and verbal number skills in preschool: Adding spatial language to the equation

Poster (2018, September)

Knowledge Discovery Approach from Blockchain, Crypto-currencies, and Financial Stock Exchanges

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 ▲]

Combining Cultural Policy History and Public History: Clearing epistemological blind spots?

Poster (2018, August)

Integrated time-resolved multi-omics for understanding microbial niche ecology

Poster (2018, August)

Microbial communities are strongly shaped by the niche breadths of their constituent populations. However, a detailed understanding of microbial niche ecology is typically lacking. Integrated multi-omic ... [more ▼]

Microbial communities are strongly shaped by the niche breadths of their constituent populations. However, a detailed understanding of microbial niche ecology is typically lacking. Integrated multi-omic analyses of host- or environment-derived samples offer the prospect of resolving fundamental and realised niches in situ. In turn, this is considered a prerequisite for niche engineering in order to drive an individual population or a community towards a specific phenotype, e.g., improvement of a biotechnological process. Here, we sampled floating islets on the surface of an activated sludge tank in a time-series spanning 51 time-points over 14 months. Multi-omics datasets (metagenomics, metatranscriptomics, metaproteomics, and (meta-)metabolomics) were generated for all time-points. Leveraging nucleotide sequencing data, we analyzed the community structure and reconstructed genomes for specific populations of interest. Moreover, based on their metabolic potential, three major groups emerged, serving as proxies for their respective fundamental niches . Time-resolved linkage of the proteomic and transcriptomic data to the reconstructed genomes revealed a fine-grained picture of niche realization. In particular, environmental factors (temperature, metabolites, oxygen) were significantly associated with gene expression of individual populations. Furthermore, we subjected the community to controlled oxygen conditions (stable or dynamic) in a bioreactor experiment and measured the transcriptomic response. Our results suggest short-term adaptations of populations of interest with respect to lipid metabolism, among other pathways. In conclusion, our work demonstrates how longitudinal multi-omic datasets can be integrated in order to further our understanding of microbial niche ecology within a biotechnological process with potential applications beyond waste water treatment. [less ▲]

Acculturation as a success story: Theoretical elaborations, lay perceptions and empirical evidence for “successful” migration in the multicultural context of Luxembourg

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 ▲]

Assessing creativity

Poster (2018, July)

Project NUMTEST: Assessing basic number competence without language

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 ▲]

A Faithful Semantic Embedding of the Dyadic Deontic Logic E in HOL

Poster (2018, June 16)

An Offline Dictionary Attack Against zkPAKE Protocol

Poster (2018, June)

Password Authenticated Key Exchange (PAKE) allows a user to establish a strong cryptographic key with a server, using only knowledge of a pre-shared password. One of the basic security requirements of ... [more ▼]

Password Authenticated Key Exchange (PAKE) allows a user to establish a strong cryptographic key with a server, using only knowledge of a pre-shared password. One of the basic security requirements of PAKE is to prevent o ine dictionary attacks. In this paper, we revisit zkPAKE, an augmented PAKE that has been recently proposed by Mochetti, Resende, and Aranha (SBSeg 2015). Our work shows that the zkPAKE protocol is prone to o ine password guessing attack, even in the presence of an adversary that has only eavesdropping capabilities. Therefore, zkPAKE is insecure and should not be used as a password-authenticated key exchange mechanism [less ▲]

Automatic discrimination of digits and letters in first graders and adults: an EEG Fast Periodic Visual Stimulation study.

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 ▲]

Logitrank Based Measures of Joint Income and Wealth Distributions: Inequality in the U.S. and Europe

Poster (2018, June)

Associations of inequality of educational opportunities and later-life cognitive trajectories

Poster (2018, May 03)

On Standardised UAV Localisation and Tracking Systems in Smart Cities

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, EUROCAE 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 ▲]

How to threaten male gamers: The effects of stereotype threat on video game performance

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 ▲]

Towards multiscale data fusion of high-resolution space borne and terrestrial datasets over Tristan da Cunha

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 ▲]

Overcoming language barriers in early mathematics instruction with “MaGrid” - a language-neutral training tool for multilingual school settings

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 ▲]

A Trellis-Based SAT Problem

Poster (2018, April)

Attitudes towards multiculturalism: Majority and minority group perspectives

Poster (2018, March 13)

When versus what: How time and valence of contextual descriptions modulate affective ERP components in response to facial expressions

Poster (2018, March)

Fourth-graders' competence beliefs in mathematics

Poster (2018, February 15)

Critical reflexivity in the professional development of professional devlopers: A co-autoethnographic exploration

Poster (2018, January)

Assessing the Performance of a Two-Step Dynamic Demand Estimation Model on Large-Scale Congested Networks

Poster (2018, January)