References of "2020"
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See detailDie Universität Luxemburg: eine dreisprachige Universität?
Wagner, Mélanie UL

in Darquennes, Jeroen; Du Plessis, Theodorus; Soler, Josep (Eds.) Sociolinguistica 34: Language diversity management in higher education (2020)

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See detailCollaboration in the 21st century: The theory, assessment, and teaching of collaborative problem solving
Graesser, Arthur C.; Greiff, Samuel UL; Stadler, Matthias et al

in Computers in Human Behavior (2020)

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See detailEditorial: Advancements in Technology-Based Assessment: Emerging Item Formats, Test Designs, and Data Sources
Goldhammer, Frank; Scherer, Ronny; Greiff, Samuel UL

in Frontiers in Psychology (2020)

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See detailNeural correlates of perceptual color inferences as revealed by #thedress
Retter, Talia UL; Gwinn, O.S.; O'Neil, S.F. et al

in Journal of Vision (2020), 20(3(7)),

Color constancy involves disambiguating the spectral characteristics of lights and surfaces, for example to distinguish red in white light from white in red light. Solving this problem appears especially ... [more ▼]

Color constancy involves disambiguating the spectral characteristics of lights and surfaces, for example to distinguish red in white light from white in red light. Solving this problem appears especially challenging for bluish tints, which may be attributed more often to shading, and this bias may underlie the individual differences in whether people described the widely publicized image of #thedress as blue-black or white-gold. To probe these higher-level color inferences, we examined neural correlates of the blue-bias, using frequency-tagging and high-density electroencephalography to monitor responses to 3-Hz alternations between different color versions of #thedress. Specifically, we compared relative neural responses to the original “blue” dress image alternated with the complementary “yellow” image (formed by inverting the chromatic contrast of each pixel). This image pair produced a large modulation of the electroencephalography amplitude at the alternation frequency, consistent with a perceived contrast difference between the blue and yellow images. Furthermore, decoding topographical differences in the blue-yellow asymmetries over occipitoparietal channels predicted blue-black and white-gold observers with over 80% accuracy. The blue-yellow asymmetry was stronger than for a “red” versus “green” pair matched for the same component differences in L versus M or S versus LM chromatic contrast as the blue-yellow pair and thus cannot be accounted for by asymmetries within either precortical cardinal mechanism. Instead, the results may point to neural correlates of a higher-level perceptual representation of surface colors. [less ▲]

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See detailUnderstanding human individuation of unfamiliar faces with oddball fast periodic visual stimulation and electroencephalography
Rossion, B.; Retter, Talia UL; Liu-Shuang, J.

in European Journal of Neuroscience (2020)

To investigate face individuation (FI), a critical brain function in the human species, an oddball fast periodic visual stimulation (FPVS) approach was recently introduced (Liu‐Shuang et al ... [more ▼]

To investigate face individuation (FI), a critical brain function in the human species, an oddball fast periodic visual stimulation (FPVS) approach was recently introduced (Liu‐Shuang et al., Neuropsychologia, 2014, 52, 57). In this paradigm, an image of an unfamiliar “base” facial identity is repeated at a rapid rate F (e.g., 6 Hz) and different unfamiliar “oddball” facial identities are inserted every nth item, at a F/n rate (e.g., every 5th item, 1.2 Hz). This stimulation elicits FI responses at F/n and its harmonics (2F/n, 3F/n, etc.), reflecting neural discrimination between oddball versus base facial identities, which is quantified in the frequency domain of the electroencephalogram (EEG). This paradigm, used in 20 published studies, demonstrates substantial advantages for measuring FI in terms of validity, objectivity, reliability, and sensitivity. Human intracerebral recordings suggest that this FI response originates from neural populations in the lateral inferior occipital and fusiform gyri, with a right hemispheric dominance consistent with the localization of brain lesions specifically affecting facial identity recognition (prosopagnosia). Here, we summarize the contributions of the oddball FPVS framework toward understanding FI, including its (a)typical development, with early studies supporting the application of this technique to clinical testing (e.g., autism spectrum disorder). This review also includes an in‐depth analysis of the paradigm's methodology, with guidelines for designing future studies. A large‐scale group analysis compiling data across 130 observers provides insights into the oddball FPVS FI response properties. Overall, we recommend the oddball FPVS paradigm as an alternative approach to behavioral or traditional event‐related potential EEG measures of face individuation. [less ▲]

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See detailA Welfare Evaluation of Green Urban Areas
Picard, Pierre M UL; Tran, Huyen

E-print/Working paper (2020)

Urban green areas cover more than 6% of urban land in Europe. This paper quan-tifies the impact of urban green areas on city structures for more than 300 Europeancities. It discusses the economic effects ... [more ▼]

Urban green areas cover more than 6% of urban land in Europe. This paper quan-tifies the impact of urban green areas on city structures for more than 300 Europeancities. It discusses the economic effects of the local amenity produced by green urbanareas using an urban economics model with various set of preferences. It estimatesthose models using data on detailed residential land uses, green urban areas and popu-lation density. It finally assesses the economic effects of reducing urban green areas incounterfactual exercises where cities are closed and open to migration and green urbanland is converted to residential plots or not. By this strategy, the economic assess-ment accounts for the general equilibrium effects through endogenous land prices andresidential space and location choices. It shows that the gross benefits of urban greenareas are substantial. A uniform removal of half of the urban green areas is equivalentto 6-9% reduction of household annual income. However, the conversion of those areasto residential plots brings a net gain of approximately 4% [less ▲]

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See detailAfter the Move to a New Campus—Effects on Students’ Satisfaction with the Physical and Learning Environment
Pinto Coelho da Costa, Andreia UL; Steffgen, Georges UL

in Education Sciences (2020)

Few empirical studies in higher education consider the importance of the physical environment on students’ satisfaction with the learning environment. The present study first examined the effects of a ... [more ▼]

Few empirical studies in higher education consider the importance of the physical environment on students’ satisfaction with the learning environment. The present study first examined the effects of a move to a new campus on students’ satisfaction with the physical and learning environments. Then, it examined how students’ satisfaction with a physical environment affects students’ satisfaction with the learning environment. It was hypothesised that the move to a new and modern university campus with better study facilities would increase students’ satisfaction both with the physical and learning environment, and that these two would be linked. Results contained 771 students’ assessments of the Bachelor Evaluation Questionnaire, which included students’ satisfaction with five aspects of their learning environment as well as five items assessing satisfaction with the physical environment. Findings showed that students were overall more satisfied with the physical environment in the new campus than in the old campus. These differences were even greater when comparing only students in their last study year than students of all study years. Furthermore, results showed that students’ satisfaction with lecturers and teaching was predicted by increased satisfaction with classrooms. The implications of these findings for the need to design physical learning environments are discussed. [less ▲]

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See detailHow big is big? How fast is fast? A Hands-On Tutorial on Mathematics of Computation
Leprevost, Franck UL

Book published by Amazon (2020)

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See detail“I Feel More Luxembourgish, but Portuguese Too” Cultural Identities in a Multicultural Society
Barros Coimbra, Stephanie UL; Albert, Isabelle UL

in Integrative Psychological and Behavioral Science (2020), 54

The present investigation focused on cultural identity and the dealing with the belonging to different cultural frames as a migrant in a highly culturally diverse context by comparing two generations of ... [more ▼]

The present investigation focused on cultural identity and the dealing with the belonging to different cultural frames as a migrant in a highly culturally diverse context by comparing two generations of Portuguese families living in Luxembourg. Quantitative standardized questionnaires complemented by in-depth qualitative interviews with parent-child dyads were used in order to assess possible (dis)similarities between first generation Portuguese immigrant parents and their adult children (i.e. second generation) concerning their cultural identities. Generational differences were found regarding the dealing with several cultural frames, language competences and attachment to both discussed cultures. Adult children were more prone to find themselves in a “compatible” identity orientation, compared to the parental generation. Yet, when focussing specifically on the second generation, qualitative data highlighted some issues regarding the perceived views of others on one’s own cultural belonging and the perception of a certain sense of cultural identity denial from others. Our findings contribute to the existing theoretical literature on cultural identity by elucidating some major differences between immigrant parents and their adult children on how they enact the sense of belonging and the dealing with multiple cultural frames on a daily-life basis. [less ▲]

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See detailThe assessment of collaborative problem solving in PISA 2015: An investigation of the validity of the PISA 2015 CPS tasks
Stadler, Matthias; Herborn, Katharina; Mustafic, Maida et al

in Computers and Education (2020)

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See detailMobile friendly design in web survey: Increasing user convenience or additional error sources?
Décieux, Jean Philippe; Sischka, Philipp UL

Scientific Conference (2020)

Relevance: At the beginning of the era of online surveys, these were programmed to be answered using desktop PCs or notebooks. However, due to technical development such as the increasing role of mobile ... [more ▼]

Relevance: At the beginning of the era of online surveys, these were programmed to be answered using desktop PCs or notebooks. However, due to technical development such as the increasing role of mobile devices, studies on online survey research detect an increase of questionnaires that are answered on mobile devices (md). However, survey navigation on md is different compared to PC: it takes place on a smaller screen and usually involves a touch pad rather than a mouse and a keyboard. Due to these differences in questionnaire navigation, some of the traditional used web question formats are no longer convenient to be answered on a md. The most common formats are matrix questions. To deal with this development, so called mobile-friendly or responsive-designs were developed, which change the layout of specific questions that are not convenient on a md into an alternative mobile-friendly-design. In case of matrixes, these were separated into item-by-item questions which are suggested to be more comfortable to answer on a mobile device. Research question: However, from a psychometric perspective the question whether these changes in question format produce comparable results is too often ignored. Therefore, this paper elucidates the following research question: Do different versions of responsive-designs actually produce equivalent response? Data & Methods: Using the data of the first two waves of the Germ and Emigration and Remigration Panelstudy we can base our analysis on more than 19.000 cases (appox. 7.000 using different md). As GERPS makes use of a responsive design, we are able to investigate measurement invariance between different md and desktop device groups. Results: As the data management is still in progress and will be finished in the end of October, we will be able to present first-hand information based on fresh data. However, first initial analyses reveal differences between md and desktop device versions. Added Value: Our study is one of the first that elucidates the equivalence of responsive design options. Thus, it enhances the perspective on the existence of possible new biases and error sources due to the increased use of md within web surveys. [less ▲]

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See detailFlipping Geometric Triangulations on Hyperbolic Surfaces
Despré, vincent; Schlenker, Jean-Marc UL; Teillaud, Monique

in symposium on computational geometry (SoCG) (2020)

We consider geometric triangulations of surfaces, i.e., triangulations whose edges can be realized by disjoint locally geodesic segments. We prove that the flip graph of geometric triangulations with ... [more ▼]

We consider geometric triangulations of surfaces, i.e., triangulations whose edges can be realized by disjoint locally geodesic segments. We prove that the flip graph of geometric triangulations with fixed vertices of a flat torus or a closed hyperbolic surface is connected. We give upper bounds on the number of edge flips that are necessary to transform any geometric triangulation on such a surface into a Delaunay triangulation. [less ▲]

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See detailConstant Gauss curvature foliations of AdS spacetimes with particles
chen, qiyu; Schlenker, Jean-Marc UL

in Transactions of the American Mathematical Society (2020), 373(6), 4013--4049

We prove that for any convex globally hyperbolic maximal (GHM) anti-de Sitter (AdS) 3-dimensional space-time N with particles (cone singularities of angles less than π along time-like curves), the ... [more ▼]

We prove that for any convex globally hyperbolic maximal (GHM) anti-de Sitter (AdS) 3-dimensional space-time N with particles (cone singularities of angles less than π along time-like curves), the complement of the convex core in N admits a unique foliation by constant Gauss curvature surfaces. This extends, and provides a new proof of, a result of \cite{BBZ2}. We also describe a parametrization of the space of convex GHM AdS metrics on a given manifold, with particles of given angles, by the product of two copies of the Teichm\"uller space of hyperbolic metrics with cone singularities of fixed angles. Finally, we use the results on K-surfaces to extend to hyperbolic surfaces with cone singularities of angles less than π a number of results concerning landslides, which are smoother analogs of earthquakes sharing some of their key properties. [less ▲]

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See detailAll-or-none face categorization in the human brain
Retter, Talia UL; Jiang, F.; Webster, M.A. et al

in NeuroImage (2020)

Visual categorization is integral for our interaction with the natural environment. In this process, similar selective responses are produced to a class of variable visual inputs. Whether categorization ... [more ▼]

Visual categorization is integral for our interaction with the natural environment. In this process, similar selective responses are produced to a class of variable visual inputs. Whether categorization is supported by partial (graded) or absolute (all-or-none) neural responses in high-level human brain regions is largely unknown. We address this issue with a novel frequency-sweep paradigm probing the evolution of face categorization responses between the minimal and optimal stimulus presentation times. In a first experiment, natural images of variable non-face objects were progressively swept from 120 to 3 ​Hz (8.33–333 ​ms duration) in rapid serial visual presentation sequences. Widely variable face exemplars appeared every 1 ​s, enabling an implicit frequency-tagged face-categorization electroencephalographic (EEG) response at 1 ​Hz. Face-categorization activity emerged with stimulus durations as brief as 17 ​ms (17–83 ​ms across individual participants) but was significant with 33 ​ms durations at the group level. The face categorization response amplitude increased until 83 ​ms stimulus duration (12 ​Hz), implying graded categorization responses. In a second EEG experiment, faces appeared non-periodically throughout such sequences at fixed presentation rates, while participants explicitly categorized faces. A strong correlation between response amplitude and behavioral accuracy across frequency rates suggested that dilution from missed categorizations, rather than a decreased response to each face stimulus, accounted for the graded categorization responses as found in Experiment 1. This was supported by (1) the absence of neural responses to faces that participants failed to categorize explicitly in Experiment 2 and (2) equivalent amplitudes and spatio-temporal signatures of neural responses to behaviorally categorized faces across presentation rates. Overall, these observations provide original evidence that high-level visual categorization of faces, starting at about 100 ​ms following stimulus onset in the human brain, is variable across observers tested under tight temporal constraints, but occurs in an all-or-none fashion. [less ▲]

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See detailMolecular force fields with gradient-domain machine learning (GDML): Comparison and synergies with classical force fields
Sauceda, Huziel E; Gastegger, Michael; Chmiela, Stefan et al

in Journal of Chemical Physics (2020)

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See detailReducing overfitting and improving generalization in training convolutional neural network under limited sample sizes in image recognition
Thanapol, Panissara UL; Lavangnananda, Kittichai; Bouvry, Pascal UL et al

in 5th International Conference on Information Technology, Bangsaen 21-22 October 2020 (2020)

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See detailFrom quantum to continuum mechanics in the delamination of atomically-thin layers from substrates
Hauseux, Paul; Nguyen, Thanh-Tung; Ambrosetti, Alberto et al

in Nature Communications (2020)

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See detailMember, Management Board, European Banking Center Network
Wolff, Christian UL

Diverse speeches and writings (2020)

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See detailMolecular basis for SARS-CoV-2 spike affinity for human ACE2 receptor
Delgado, Julian M; Duro, Nalvi; Rogers, David M et al

in bioRxiv (2020)

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See detailSYMBOL LEVEL PRECODING TECHNIQUES FOR HARDWARE AND POWER EFFICIENT WIRELESS TRANSCEIVERS
Domouchtsidis, Stavros UL

Doctoral thesis (2020)

Large-scale antennas are crucial for next generation wireless communication systems as they improve spectral efficiency, reliability and coverage compared to the traditional ones that are employing ... [more ▼]

Large-scale antennas are crucial for next generation wireless communication systems as they improve spectral efficiency, reliability and coverage compared to the traditional ones that are employing antenna arrays of few elements. However, the large number of antenna elements leads to a big increase in power consumption of conventional fully digital transceivers due to the one Radio Frequency (RF) chain / per antenna element requirement. The RF chains include a number of different components among which are the Digital-to-Analog Converters (DACs)/Analog-to-Digital Converters (ADCs) that their power consumption increases exponential with the resolution they support. Motivated by this, in this thesis, a number of different architectures are proposed with the view to reduce the power consumption and the hardware complexity of the transceiver. In order to optimize the transmission of data through them, corresponding symbol level precoding (SLP) techniques were developed for the proposed architectures. SLP is a technique that mitigates multi-user interference (MUI) by designing the transmitted signals using the Channel State Information and the information-bearing symbols. The cases of both frequency flat and frequency selective channels were considered. First, three different power efficient transmitter designs for transmission over frequency flat channels and their respective SLP schemes are considered. The considered systems tackle the high hardware complexity and power consumption of existing SLP techniques by reducing or completely eliminating fully digital RF chains. The precoding design is formulated as a constrained least squares problem and efficient algorithmic solutions are developed via the Coordinate Descent method. Next, the case of frequency selective channels is considered. To this end, Constant Envelope precoding in a Multiple Input Multiple Output Orthogonal Frequency Division Multiplexing system (CE MIMO-OFDM) is considered. In CE MIMO-OFDM the transmitted signals for each antenna are designed to have constant amplitude regardless of the channel realization and the information symbols that must be conveyed to the users. This facilitates the use of power-efficient components, such as phase shifters and non-linear power amplifiers. The precoding problem is firstly formulated as a least-squares problem with a unit-modulus constraint and solved using an algorithm based on the coordinate descent (CCD) optimization framework and then, after reformulating the problem into an unconstrained non-linear least squares problem, a more computationally efficient solution using the Gauss-Newton algorithm is presented. Then, CE MIMO-OFDM is considered for a system with low resolution DACs. The precoding design problem is formulated as a mixed discrete- continuous least-squares optimization one which is NP-hard. An efficient low complexity solution is developed based also on the CCD optimization framework. Finally, a precoding scheme is presented for OFDM transmission in MIMO systems based on one-bit DACs and ADCs at the transmitter’s and the receiver’s end, respectively, as a way to reduce the total power consumption. The objective of the precoding design is to mitigate the effects of one-bit quantization and the problem is formulated and then is split into two NP hard least squares optimization problems. Algorithmic solutions are developed for the solution of the latter problems, based on the CCD framework. [less ▲]

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