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See detailEvaluating Pretrained Transformer-based Models on the Task of Fine-Grained Named Entity Recognition
Lothritz, Cedric UL; Allix, Kevin UL; Veiber, Lisa UL et al

in Proceedings of the 28th International Conference on Computational Linguistics (2020, December)

Named Entity Recognition (NER) is a fundamental Natural Language Processing (NLP) task and has remained an active research field. In recent years, transformer models and more specifically the BERT model ... [more ▼]

Named Entity Recognition (NER) is a fundamental Natural Language Processing (NLP) task and has remained an active research field. In recent years, transformer models and more specifically the BERT model developed at Google revolutionised the field of NLP. While the performance of transformer-based approaches such as BERT has been studied for NER, there has not yet been a study for the fine-grained Named Entity Recognition (FG-NER) task. In this paper, we compare three transformer-based models (BERT, RoBERTa, and XLNet) to two non-transformer-based models (CRF and BiLSTM-CNN-CRF). Furthermore, we apply each model to a multitude of distinct domains. We find that transformer-based models incrementally outperform the studied non-transformer-based models in most domains with respect to the F1 score. Furthermore, we find that the choice of domains significantly influenced the performance regardless of the respective data size or the model chosen. [less ▲]

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See detailQuantum friction in the Hydrodynamic Model
Wu, Kunmin UL; Schmidt, Thomas UL; Farias, Maria Belen UL

E-print/Working paper (2020)

We study the phenomenon of quantum friction in a system consisting of a polarizable atom moving at a constant speed parallel to a metallic plate. The metal is described using a charged hydrodynamic model ... [more ▼]

We study the phenomenon of quantum friction in a system consisting of a polarizable atom moving at a constant speed parallel to a metallic plate. The metal is described using a charged hydrodynamic model for the electrons. This model featuring long-range interactions is appropriate for a clean metal in a temperature range where scattering due to Coulomb interactions dominates over the scattering of electron by impurities. We find that a quantum friction force between the atom and the metal surface exists even in the absence of intrinsic damping in the metal, but that it only starts once the velocity of the atom exceeds the effective speed of sound in the metal. We argue that this condition can be fulfilled most easily in metals with nearly empty or nearly filled bands. We make quantitative predictions for the friction force to the second and fourth order in the atomic polarizability, and show that the threshold behavior persists to all orders of the perturbation theory. [less ▲]

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See detailAR4OER: A Semantic Platform for Open Educational Augmented Reality Resources
Grevisse, Christian UL; Martins Gomes, Carina; Rothkugel, Steffen UL

in Proceedings of the 2020 IEEE International Symposium on Multimedia (2020, December)

Tablet computers are gaining in presence in modern-day classrooms, enabling the use of a variety of apps for purposes such as note-taking or assessment. Augmented Reality (AR) experiences in the classroom ... [more ▼]

Tablet computers are gaining in presence in modern-day classrooms, enabling the use of a variety of apps for purposes such as note-taking or assessment. Augmented Reality (AR) experiences in the classroom, made possible by current hardware, permit new ways of interaction and visualization, as well as increase student motivation and engagement. They also overcome the need for potentially expensive hardware required for experiments in certain scientific domains. The movement of Open Educational Resources (OER) has enabled the sharing of heterogeneous learning resources. Their retrieval can be improved by enriching their metadata using Semantic Web technologies. In this paper, we present AR4OER, a semantic platform for heterogeneous AR experiences provided as OER. We showcase four AR scenarios from different school subjects. These scenarios can be integrated through a lose coupling in third-party apps. Apart from describing how this integration works, we demonstrate how a note-taking app can benefit from these scenarios. [less ▲]

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See detailÉcologie culturelle et cultures écologiques dans la Grande Région / Kulturökologie und ökologische Kulturen in der Großregion
Thiltges, Sébastian UL; Solte-Gresser, Christiane

Book published by Peter Lang (2020)

Menschengemachter Klimawandel, urbane und rurale Lebenswelten, lokale und globale Umweltbewegungen: Bei all diesen Themen und Debatten geht es um die Beziehungen zwischen Natur und Kultur. Angesichts der ... [more ▼]

Menschengemachter Klimawandel, urbane und rurale Lebenswelten, lokale und globale Umweltbewegungen: Bei all diesen Themen und Debatten geht es um die Beziehungen zwischen Natur und Kultur. Angesichts der Dominanz ökologischer Fragen in Wissenschaft, Wirtschaft und Politik stellt dieses Buch dezidiert kulturelle Umwelt-Diskurse in den Mittelpunkt: Wie lassen sich die rasanten, bislang kaum vorstellbaren ökologischen Veränderungen erfassen, erzählen und imaginieren? Am Beispiel des grenzüberschreitenden Raumes der europäischen Großregion (Lothringen, Luxemburg, Rheinland-Pfalz, Saarland, Wallonien) regen die Environmental Humanities mit ihrer transdisziplinären Perspektive dazu an, die vielfältigen Interaktionen zwischen Menschen und Nicht-Menschen in einem gemeinsamen ökokulturellen Raum neu zu denken. [less ▲]

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See detailOpinion Statement ECJ-TF 2/2020 on the ECJ Decision of 3 March 2020 in Vodafone Magyarország Mobil Távközlési Zrt. (Case C-75/18) on Progressive Turnover Taxes
García Prats, Alfredo; Haslehner, Werner UL; Heydt, Volker et al

in European Taxation (2020), 60(12), 555-564

This CFE Opinion Statement discusses the decision of the Grand Chamber of the ECJ in Vodafone. The Court held that the imposition of the Hungarian progressive turnover-based tax on the telecommunications ... [more ▼]

This CFE Opinion Statement discusses the decision of the Grand Chamber of the ECJ in Vodafone. The Court held that the imposition of the Hungarian progressive turnover-based tax on the telecommunications sector did not infringe the EU fundamental freedoms or article 401 of the VAT Directive (2006/112), and that the question regarding the prohibition of State aid was inadmissible. Vodafone is especially important in respect of the current debate regarding turnover-based digital services taxes. [less ▲]

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See detailTHIS TIME IS REALLY DIFFERENT: FLIGHT-TO-SAFETY AND THE COVID-19 CRISIS
Löwen, Celina; Kchouri, Bilal UL; Lehnert, Thorsten UL

E-print/Working paper (2020)

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See detailHybrid Attitude Control for Nano-Spacecraft: Reaction Wheel Failure and Singularity Handling
Mahfouz, Ahmed UL; Pritykin, Dmitry; Biggs, James

in Journal of Guidance Control and Dynamics (2020), 44(3), 548-558

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See detailPour une nouvelle pratique de l’appel immédiat !
Menetrey, Séverine UL

in Pasicrisie Luxembourgeoise: Recueil Trimestriel de la Jurisprudence Luxembourgeoise (2020), t. 39, 4/2020

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See detailWireless Edge Caching: Modeling, Analysis, and Optimization
Vu, Thang Xuan UL; Bastug, Ejder; Chatzinotas, Symeon UL et al

Book published by Cambridge University Press (2020)

Understand both uncoded and coded caching techniques in future wireless network design. Expert authors present new techniques that will help you to improve backhaul, load minimization, deployment cost ... [more ▼]

Understand both uncoded and coded caching techniques in future wireless network design. Expert authors present new techniques that will help you to improve backhaul, load minimization, deployment cost reduction, security, energy efficiency and the quality of the user experience. Covering topics from high-level architectures to specific requirement-oriented caching design and analysis, including big-data enabled caching, caching in cloud-assisted 5G networks, and security, this is an essential resource for academic researchers, postgraduate students and engineers working in wireless communications. [less ▲]

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See detailConstant Envelope MIMO-OFDM Precoding for Low Complexity Large-Scale Antenna Array Systems
Domouchtsidis, Stavros UL; Tsinos, Christos UL; Chatzinotas, Symeon UL et al

in IEEE Transactions on Wireless Communications (2020)

Herein, we consider constant envelope precoding in a multiple-input multiple-output orthogonal frequency division multiplexing system (CE MIMO-OFDM) for frequency selective channels. In CE precoding the ... [more ▼]

Herein, we consider constant envelope precoding in a multiple-input multiple-output orthogonal frequency division multiplexing system (CE MIMO-OFDM) for frequency selective channels. In CE precoding the signals for each transmit 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 (PS) and nonlinear power amplifiers, which are key for the feasibility of large-scale antenna array systems because of their low cost and power consumption. The CE precoding problem is firstly formulated as a least-squares problem with a unit modulus constraint and solved using an algorithm based on coordinate descent. The large number of optimization variables in the case of the MIMO-OFDM system motivates the search for a more computationally efficient solution. To tackle this, we reformulate the CE precoding design into an unconstrained nonlinear least-squares problem, which is solved efficiently using the Gauss-Newton algorithm. Simulation results underline the efficiency of the proposed solutions and show that they outperform state of the art techniques. [less ▲]

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See detailLes anciens légionnaires et la protection sociale au Luxembourg. Une approche transnationale
Venken, Machteld UL

in Camarda, Sandra; Reinert, Francoise; Sauer, Arnaud (Eds.) et al Légionnaires. Parcours de guerre et de migrations entre le Luxembourg et la France. (2020)

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See detailA comparison of constitutive models for describing the flow of uncured styrene-butadiene rubber
Rehor, Martin UL; Gansen, Alex UL; Sill, Clemens et al

in Journal of Non-Newtonian Fluid Mechanics (2020), 286

Uncured styrene-butadiene rubber (SBR) can be modelled as a viscoelastic material with at least two different relaxation mechanisms. In this paper we compare multi-mode constitutive models combining two ... [more ▼]

Uncured styrene-butadiene rubber (SBR) can be modelled as a viscoelastic material with at least two different relaxation mechanisms. In this paper we compare multi-mode constitutive models combining two viscoelastic modes (linear and/or nonlinear) in three possible ways. Our particular choice of the two modes was inspired by models originally developed to describe the response of asphalt binders. We select the model that best fits the experimental data obtained from a modified stress relaxation experiment in the torsional configuration of the plate-plate rheometer. The optimisation of the five model parameters for each model is achieved by minimising the weighted least-squares distance between experimental observations and the computer model output using a tree-structured Parzen estimator algorithm to find an initial guess, followed by further optimisation using the Nelder-Mead simplex algorithm. The results show that the model combining the linear mode and the nonlinear mode is the most suitable variant to describe the observed behavior of SBR in the given regime. The predictive capabilities of the three models are further examined in changed experimental and numerical configurations. Full data and code to produce the figures in this article are included as supplementary material. [less ▲]

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See detailImmersions of surfaces into SL(2,C) and into the space of geodesics of Hyperbolic space
El Emam, Christian UL

Doctoral thesis (2020)

This thesis mainly treats two developments of the classical theory of hypersurfaces inside pseudo-Riemannian space forms. The former - a joint work with Francesco Bonsante - consists in the study of ... [more ▼]

This thesis mainly treats two developments of the classical theory of hypersurfaces inside pseudo-Riemannian space forms. The former - a joint work with Francesco Bonsante - consists in the study of immersions of smooth manifolds into holomorphic Riemannian space forms of constant curvature -1 (including SL(2,C) with a multiple of its Killing form): this leads to a Gauss-Codazzi theorem, it suggests an approach to holomorphic transitioning of immersions into pseudo-Riemannian space forms, a trick to construct holomorphic maps into the PSL(2,C)-character variety, and leads to a restatement of Bers theorem. The latter - a joint work with Andrea Seppi - consists in the study of immersions of n-manifolds inside the space of geodesics of the hyperbolic (n+1)-space. We give a characterization, in terms of the para-Kahler structure of this space of geodesics, of the Riemannian immersions which turn out to be Gauss maps of equivariant immersions into the hyperbolic space. [less ▲]

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See detailJoint User Grouping, Scheduling, and Precoding for Multicast Energy Efficiency in Multigroup Multicast Systems
Bandi, Ashok UL; Mysore Rama Rao, Bhavani Shankar UL; Chatzinotas, Symeon UL et al

in IEEE Transactions on Wireless Communications (2020)

This paper studies the joint design of user grouping, scheduling (or admission control) and precoding to optimize energy efficiency (EE) for multigroup multicast scenarios in single-cell multiuser MISO ... [more ▼]

This paper studies the joint design of user grouping, scheduling (or admission control) and precoding to optimize energy efficiency (EE) for multigroup multicast scenarios in single-cell multiuser MISO downlink channels. Noticing that the existing definition of EE fails to account for group sizes, a new metric called multicast energy efficiency (MEE) is proposed. In this context, the joint design is considered for the maximization of MEE, EE, and scheduled users. Firstly, with the help of binary variables (associated with grouping and scheduling) the joint design problem is formulated as a mixed-Boolean fractional programming problem such that it facilitates the joint update of grouping, scheduling and precoding variables. Further, several novel optimization formulations are proposed to reveal the hidden difference of convex/ concave structure in the objective and associated constraints. Thereafter, we propose a convex-concave procedure framework based iterative algorithm for each optimization criteria where grouping, scheduling, and precoding variables are updated jointly in each iteration. Finally, we compare the performance of the three design criteria concerning three performance metrics namely MEE, EE, and scheduled users through Monte-Carlo simulations. These simulations establish the need for MEE and the improvement from the system optimization. [less ▲]

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See detailRoad to effective data curation for translational research
Gu, Wei UL; Hasan, Samiul; Rocca-Serra, Philippe et al

in Drug Discovery Today (2020)

Translational research today is data-intensive and requires multi-stakeholder collaborations to generate and pool data together for integrated analysis. This leads to the challenge of harmonization of ... [more ▼]

Translational research today is data-intensive and requires multi-stakeholder collaborations to generate and pool data together for integrated analysis. This leads to the challenge of harmonization of data from different sources with different formats and standards, which is often overlooked during project planning and thus becomes a bottleneck of the research progress. We report on our experience and lessons learnt about data curation for translational research garnered over the course of the eTRIKS program (https://www.etriks.org), a unique, 5-year, cross-organizational, cross-cultural collaboration project funded by the Innovative Medicines Initiative of the EU. Here, we discuss the obstacles and suggest what steps are needed for effective data curation in translational research, especially for projects involving multiple organizations from academia and industry. [less ▲]

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See detailSimultaneous Diagonalization of Incomplete Matrices and Applications
Coron, Jean-Sébastien UL; Notarnicola, Luca UL; Wiese, Gabor UL

in Proceedings of the Fourteenth Algorithmic Number Theory Symposium (ANTS-XIV), edited by Steven Galbraith, Open Book Series 4, Mathematical Sciences Publishers, Berkeley, 2020 (2020, December)

We consider the problem of recovering the entries of diagonal matrices {U_a}_a for a = 1, . . . , t from multiple “incomplete” samples {W_a}_a of the form W_a = P U_a Q, where P and Q are unknown matrices ... [more ▼]

We consider the problem of recovering the entries of diagonal matrices {U_a}_a for a = 1, . . . , t from multiple “incomplete” samples {W_a}_a of the form W_a = P U_a Q, where P and Q are unknown matrices of low rank. We devise practical algorithms for this problem depending on the ranks of P and Q. This problem finds its motivation in cryptanalysis: we show how to significantly improve previous algorithms for solving the approximate common divisor problem and breaking CLT13 cryptographic multilinear maps. [less ▲]

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See detailDouble-Graded Quantum Superplane
Bruce, Andrew UL; Duplij, Steven

in Reports on Mathematical Physics (2020), 86(3), 383-400

A ℤ2 × ℤ2-graded generalisation of the quantum superplane is proposed and studied. We construct a bicovariant calculus on what we shall refer to as the double-graded quantum superplane. The ommutation ... [more ▼]

A ℤ2 × ℤ2-graded generalisation of the quantum superplane is proposed and studied. We construct a bicovariant calculus on what we shall refer to as the double-graded quantum superplane. The ommutation rules between the coordinates, their differentials and partial derivatives are explicitly given. Furthermore, we show that an extended version of the double-graded quantum superplane admits a natural Hopf -algebra structure. [less ▲]

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