Robust Real-time Sense-and-Avoid Solutions for Remotely Piloted Quadrotor UAVs in Complex Environments

Doctoral thesis (2020)

UAV teleoperation is a demanding task: to successfully accomplish the mission without collision requires skills and experience. In real-life environments, current commercial UAVs are to a large extent ... [more ▼]

UAV teleoperation is a demanding task: to successfully accomplish the mission without collision requires skills and experience. In real-life environments, current commercial UAVs are to a large extent remotely piloted by amateur human pilots. Due to lack of teleoperation experience or skills, they often drive UAVs into collision. Therefore, in order to ensure safety of the UAV as well as its surroundings, it is necessary for the UAV to boast the capability of detecting emergency situation and acting on its own when facing imminent threat. However, the majority of UAVs currently available in the market are not equipped with such capability. To fill in the gap, in this work we present 2D LIDAR based Sense-and-Avoid solutions which are able to actively assist unskilled human operator in obstacle avoidance, so that the operator can focus on high-level decisions and global objectives in UAV applications such as search and rescue, farming etc. Specifically, with our novel 2D LIDAR based obstacle detection and tracking algorithm, perception-assistive flight control design, progressive emergency evaluation policies and optimization based and adaptive virtual cushion force field (AVCFF) based avoidance strategies, our proposed UAV teleoperation assistance systems are capable of obstacle detection and tracking, as well as automatic obstacle avoidance in complex environment where both static and dynamic objects are present. Additionally, while the optimization based solution is validated in Matlab, the AVCFF based avoidance system has been fully integrated with sensing system, perception-assistive flight controller on the basis of the Hector Quadrotor open source framework, and the effectiveness of the complete Sense-and-Avoid solution has been demonstrated and validated on a realistic simulated UAV platform in Gazebo simulations, where the UAV is operated at a high speed. [less ▲]

Le Luxembourg, bien plus qu'un espace intermédiaire

Article for general public (2020)

Lehrende und Schüler im Film: Performanzen, Ansprüche, Begehren und Geniessen in Bildungsprozessen.

Scientific Conference (2020, December 05)

Das Kino ist ein pädagogisches Institut, das unsere Fantasien formt. Es sagt uns, wie wir überhaupt begehren können, behauptet der Kulturtheoretiker und Psychoanalytiker Slavoj Zizek. So ist es sinnvoll ... [more ▼]

Das Kino ist ein pädagogisches Institut, das unsere Fantasien formt. Es sagt uns, wie wir überhaupt begehren können, behauptet der Kulturtheoretiker und Psychoanalytiker Slavoj Zizek. So ist es sinnvoll, sich als Lehrerinnen für die filmischen Inszenierungen des Lehrens und Lernens zu interessieren und sich durch sie «an-sprechen» und affizieren zu lassen. Der Workshop gilt als Austausch über markante Ausschnitte in denen Lehrer, Schule oder Unterricht Subjektwerden bzw. in ihrer Subjektivation und Humanisation blockiert sind. Bestimmte Symptome des kollektiven und individuellen Imaginären sollen freigelegt werden. Dabei stellt sich auch die Frage, inwiefern man mit Hilfe dieser (Re)-Inszenierungen des Lehrens auf der Leinwand anthropologische und strukturelle Elemente des Lehrens und von transformatorischen Bildungsprozessen erschließen kann. Besonderes Interesse gilt dabei der Frage, wie Lehrerinnen im Spielfilm Singularität und Kollektivität erfolgreich artikulieren oder dabei scheitern. [less ▲]

L'Europe des droits fondamentaux

Article for general public (2020)

Sept décennies après la signature de la Convention européenne des droits de l’homme (Rome, 4 novembre 1950) et vingt ans après la proclamation la Charte des droits fondamentaux de l’Union européenne (Nice ... [more ▼]

Sept décennies après la signature de la Convention européenne des droits de l’homme (Rome, 4 novembre 1950) et vingt ans après la proclamation la Charte des droits fondamentaux de l’Union européenne (Nice, 7 décembre 2000), la sauvegarde des libertés fondamentales et de l’État de droit mis en cause par certains État membres se trouvent parmi les défis majeurs de l’Europe. À l’heure ou l’Union cherche des réponses pour contrecarrer les atteintes portées à son socle des valeurs communes, un regard rétrospectif sur la problématique européenne des libertés et droits fondamentaux permettra de mieux comprendre la gravité des enjeux actuels. [less ▲]

What is problematic about binary questions on gender in health surveys – a missing answer analysis

in Cogent Medicine (2020, December 04)

Background: In many studies, participants who do not state their gender are excluded from the analysis. This may be appropriate if they do not answer the questionnaire seriously. However, some ... [more ▼]

Background: In many studies, participants who do not state their gender are excluded from the analysis. This may be appropriate if they do not answer the questionnaire seriously. However, some participants may have understandable reasons for not reporting their gender, e.g. questioning their gender identity. Research question: How many students and which students do not answer the question on gender? Methods: We analyzed data of the Health Behaviour in School-aged Children study from Ireland, France, Hungary, Scotland, Belgium (Flemish) and Luxembourg (n = 40,053). To explore the reasons for non-response, we divided the participants into 3 groups: 1. Responders answered both socio- demographic questions (age and gender) 2. age non-responders did not answer the question on age. 3. Gender non-responders answered the question on age, but not the one on gender. Results: 311 out of 40,053 (0.8%) pupils aged 11–18 did not report their gender. About 40% of them did not answer the age question either. However, the other 60% belong to the group of gender non-responders and this group is disadvantaged compared to responders: they report lower self-rated health, more health complaints, less family support and more substance use (alcohol, tobacco, cannabis). 1.9% of pupils did not answer the question about age. These age non-responders answered the questionnaire more selectively overall and skipped more questions. Conclusion: The data suggest that the reasons for age non-response and gender non-response are different. For age non-responders, the fear of de-anonymization seems to be the reason for not indicating their age. Not answering the question on gender is rare. If the participants answered the question on age, but not the question on gender, then the variable gender is missing not at random. The health problems of gender non-responders correspond to the health problems of gender non-conforming adolescents. Thus, the question arises if the group of gender non-responders should be included in the analysis and if the question on gender should be asked differently in the future [less ▲]

Strengthening links between multilingual practices in professional environments and university language programmes

Presentation (2020, December 04)

Lorsque les pratiques multilingues en contexte professionnel international sont encadrées par des politiques linguistiques, elles donnent un point d’ancrage pour mesurer les oscillations entre le « ... [more ▼]

Lorsque les pratiques multilingues en contexte professionnel international sont encadrées par des politiques linguistiques, elles donnent un point d’ancrage pour mesurer les oscillations entre le « prescrit » et l’«existant ». La caractérisation des pratiques multilingues d’une entreprise aéronautique européenne et de l’UNESCO demande de placer notre recherche à la croisée des champs de la linguistique, de la didactique des langues, de la sociologie, et de la psychologie sociale et cognitive. Nous allons présenter les résultats d’analyse des besoins déclarés par les salariés eux-mêmes, des interactions enregistrées en réunions et aussi des bilans d’entretiens. Ces deux terrains de recherche ont des caractéristiques linguistiques similaires : l’utilisation de l’anglais comme langue véhiculaire, la localisation d’un site à Hambourg en Allemagne, leurs sièges sociaux respectifs en France, des communications régulières avec des sites en zone hispanophone, ainsi que l’offre de cours d’anglais, de français, d’allemand et d’espagnol auprès de leurs employés. La polyphonie des discours sur les pratiques multilingues en entreprise montre les tensions existantes entre le choix de l’usage de l’anglais comme lingua franca et celui du français, de l’allemand et de l’espagnol qui ouvre différents « univers du discours » (Charolles 1997). A partir de la question de cadrage, envisagé au plan linguistique comme au plan sociologique, nous essayons d’établir le lien entre posture professionnelle et pratiques langagières. Il semblerait que les faits de pluri-compétences, de pluri-linguisme, de multi-linguisme et de pluri-activités donnent matière à repenser nos méthodologies d’enseignement des langues. Par ailleurs. La relation d’aide (Amério 1991, Lejot 2014) entre les employés favorise le développement des compétences linguistiques dans la langue cible. Notre objectif est ici de faire un lien entre les besoins linguistiques et culturels identifiés en milieu professionnel et le développement des compétences multilingues en milieu universitaire. La personne bilingue n’est pas une somme de deux personnes monolingues (Grosjean 1989), et au même titre, l’enseignement plurilingue n’est pas une somme d’enseignements monolingues au sein d’une même formation en langues appliquées. Des recherches en linguistiques comparatistes (Huemer, Lejot, Deroey 2019) et des méthodes pédagogiques basées sur l’autonomie de l’étudiant ouvrent des perspectives à explorer ou à approfondir. [less ▲]

Effektive Rechtsdurchsetzung - Was der Digital Services Act leisten sollte

in epd medien (2020), 2020(49), 6-10

Die Europäische Kommission will mit dem „Digital Services Act“ die Richtlinie über elektronischen Handel im Binnenmarkt (ECommerce- Richtlinie) novellieren und erweitern. Ziel ist eine moderne ... [more ▼]

Die Europäische Kommission will mit dem „Digital Services Act“ die Richtlinie über elektronischen Handel im Binnenmarkt (ECommerce- Richtlinie) novellieren und erweitern. Ziel ist eine moderne Gesetzgebung für die Online-Welt; für digitale Dienste sollen klare Verantwortlichkeiten festgelegt werden (epd 37, 38, 40, 44/20). Ein Entwurf für das Gesetzespaket soll am 9. Dezember vorgestellt werden. Mark D. Cole, Wissenschaftlicher Direktor des Instituts für Europäisches Medienrecht (EMR) in Saarbrücken, hat mit seinem Team im Auftrag der Landesanstalt für Medien NRW eine Studie erstellt, die sich mit der Reform des Rechtsrahmens bei der grenzüberschreitenden Verbreitung von Online-Inhalten befasst und dabei legislative Optionen der Europäischen Union (EU) in den Blick nimmt. Die Untersuchung knüpft an eine umfassende Studie an, die den aktuellen Regelungsrahmen und insbesondere die E-Commerce-Richtlinie auf Reformbedarf untersucht hat (Zusammenfassungen von beiden Studien: 􀀀http:// u.epd.de/1p2c). In seinem Beitrag für epd medien leitet Cole, der auch Professor für Medienund Telekommunikationsrecht an der Universität Luxemburg ist, aus diesen Überlegungen konkrete Ansätze für den europäischen Gesetzgeber ab. [less ▲]

Tertium non datur: Various aspects of value-added (VA) models used as measures of educational effectiveness

Doctoral thesis (2020)

Value-added (VA) models are used as measures of educational effectiveness which aim to find the “value” that has been added by teachers or schools to students’ achievement, independent of students’ ... [more ▼]

Value-added (VA) models are used as measures of educational effectiveness which aim to find the “value” that has been added by teachers or schools to students’ achievement, independent of students’ backgrounds. Statistically speaking, teacher or school VA scores are calculated as the part of an outcome variable that cannot be explained by the covariates that are in the VA model (i.e., the residual). Teachers or schools are classified as effective (or ineffective) if they have a positive (or negative) effect on students’ achievement compared to a previously specified norm value. Although VA models have gained popularity in recent years, there is a lack of consensus concerning various aspects of VA scores. The present dissertation aims at shedding light on these aspects, including the state of the art of VA research in the international literature, covariate choice, and model selection for the estimation of VA scores. In a first step, a systematic literature review was conducted, in which 370 studies from 26 countries were classified, focusing on methodological issues (Study 1 of the present dissertation). Results indicated no consensus concerning the applied statistical model type (the majority applied a linear regression, followed by multilevel models). Concerning the covariate choice, most studies used prior achievement as a covariate, cognitive and/or motivational student data were hardly considered, and there was no consensus on the in- or exclusion of students’ background variables. Based on these findings, it was suggested that VA models are better suited to improve the quality of teaching than for accountability and decision-making purposes. Secondly, based on one of the open questions resulting from Study 1 (i.e., covariate choice), the aim of Study 2 was to systematically compare different covariate combinations in the estimation of school VA models. Based on longitudinal data from primary school students participating in the Luxembourg School Monitoring Programme in Grades 1 and 3, three covariate sets were found to be essential when calculating school VA scores with math or language achievement as dependent variables: prior language achievement, prior math achievement, and students’ sociodemographic and sociocultural background. However, the evaluation of individual schools’ effectiveness varied widely depending on the covariate set that was chosen, casting further doubt on the use of VA scores for accountability purposes. Thirdly, the aim of Study 3 was to investigate statistical model selection, as Study 1 showed no consensus on which model types are most suitable for the estimation of VA scores, with the majority of studies applying linear regression or multilevel models. These classical linear models, along with nonlinear models and different types of machine learning models were systematically compared to each other. Covariates were kept constant (based on the results from Study 2) across models. Multilevel models led to the most accurate prediction of students’ achievement. However, as school VA scores varied depending on specific model choices and as these results can be only generalized for a Luxembourgish sample, it was suggested for future research that the model selection process should be made transparent and should include different specifications in order to obtain ranges of potential VA scores. In conclusion, all three studies imply that the application of VA models for decision-making and accountability should be critically discussed and that VA scores should not be used as the only measure for accountability or high-stakes decisions. In addition, it can be concluded that VA scores are more suitable for informative purposes. Thus, the findings from the present dissertation prepare the ground for future research, where schools with stable high VA scores can be part of further investigations (both qualitatively and quantitatively) to study their pedagogical strategies and learn from them. [less ▲]

Homogeneous selection promotes microdiversity in the glacier-fed stream microbiome

E-print/Working paper (2020)

Microdiversity, the organization of microorganisms into groups with closely related but ecologically different sub-types, is widespread and represents an important linchpin between microbial ecology and ... [more ▼]

Microdiversity, the organization of microorganisms into groups with closely related but ecologically different sub-types, is widespread and represents an important linchpin between microbial ecology and evolution. However, the drivers of microdiversification remain largely unknown. Here we show that selection promotes microdiversity in the microbiome associated with sediments in glacier-fed streams (GFS). Applying a novel phylogenetic framework, we identify several clades that are under homogeneous selection and that contain genera with higher levels of microdiversity than the rest of the genera. Overall these clades constituted ~44% and ~64% of community α-diversity and abundance, and both percentages increased further in GFS that were largely devoid of primary producers. Our findings show that strong homogeneous selection drives the microdiversification of specialized microbial groups putatively underlying their success in the extreme environment of GFS. This microdiversity could be threatened as glaciers shrink, with unknown consequences for microbial diversity and functionality in these ecosystems. [less ▲]

A newform theory for Katz modular forms

Doctoral thesis (2020)

In this thesis, a strong multiplicity one theorem for Katz modular forms is studied. We show that a cuspidal Katz eigenform which admits an irreducible Galois representation is in the level and weight old ... [more ▼]

In this thesis, a strong multiplicity one theorem for Katz modular forms is studied. We show that a cuspidal Katz eigenform which admits an irreducible Galois representation is in the level and weight old space of a uniquely associated Katz newform. We also set up multiplicity one results for Katz eigenforms which have reducible Galois representation. [less ▲]