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See detailThe Dark Side of Digital Financial Transformation: The New Risks of FinTech and the Rise of TechRisk
Zetzsche, Dirk Andreas UL; Arner, Douglas; Buckley, Ross

in Singapore Journal of Legal Studies (in press)

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See detailSustainability, FinTech and Financial Inclusion
Zetzsche, Dirk Andreas UL; Veidt, Robin UL; Buckley, Ross et al

in European Business Organization Law Review (in press)

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See detailThe EU’s Impact on Data-driven Finance
Zetzsche, Dirk Andreas UL; Buckley, Ross; Arner, Douglas et al

in Common Market Law Review (in press)

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See detailBrownian Loops, Layering Fields and Imaginary Gaussian Multiplicative Chaos
Camia, Federico; Gandolfi, Alberto; Peccati, Giovanni UL et al

in Communications in Mathematical Physics (2021), In press

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See detailA quasicontinuum approach towards mechanical simulations of periodic lattice structures
Chen, Li UL

Doctoral thesis (2021)

Thanks to the advancement of additive manufacturing, periodic metallic lattice structures are gaining more and more attention. A major attraction of them is that their design can be tailored to specific ... [more ▼]

Thanks to the advancement of additive manufacturing, periodic metallic lattice structures are gaining more and more attention. A major attraction of them is that their design can be tailored to specific applications by changing the basic repetitive pattern of the lattice, called the unit cell. This may involve the selection of optimal strut diameters and orientations, as well as the connectivity and strut lengths. Numerical simulation plays a vital role in understanding the mechanical behavior of metallic lattices and it enables the optimization of design parameters. However, conventional numerical modeling strategies in which each strut is represented by one or more beam finite elements yield prohibitively time­consuming simulations for metallic lattices in engineering­scale applications. The reasons are that millions of struts are involved, as well as that geometrical and material nonlinearities at the strut level need to be incorporated. The aim of this thesis is the development of multi­scale quasicontinuum (QC) frameworks to substantially reduce the simulation time of nonlinear mechanical models of metallic lattices. For this purpose, this thesis generalizes the QC method by a multi­field interpolation enabling amongst others the representation of varying diameters in the struts’ axial directions (as a consequence of the manufacturing process). The efficiency is further increased by a new adaptive scheme that automatically adjusts the model reduction whilst controlling the (elastic or elastoplastic) model’s accuracy. The capabilities of the proposed methodology are demonstrated using numerical examples, such as indentation tests and scratch tests, in which the lattice is modeled using geometrically nonlinear elastic and elastoplastic beam finite elements. They show that the multi­scale framework combines a high accuracy with substantial model reduction that are out of reach of direct numerical simulations. [less ▲]

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See detailTesting market regulations in experimental asset markets –The case of margin purchases
Neugebauer, Tibor UL; Füllbrunn, Sascha

in Journal of Economic Behavior and Organization (2021)

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See detailConFuzzius: A Data Dependency-Aware Hybrid Fuzzer for Smart Contracts
Ferreira Torres, Christof UL; Iannillo, Antonio Ken UL; Gervais, Arthur et al

in European Symposium on Security and Privacy, Vienna 7-11 September 2021 (2021, September)

Smart contracts are Turing-complete programs that are executed across a blockchain. Unlike traditional programs, once deployed, they cannot be modified. As smart contracts carry more value, they become ... [more ▼]

Smart contracts are Turing-complete programs that are executed across a blockchain. Unlike traditional programs, once deployed, they cannot be modified. As smart contracts carry more value, they become more of an exciting target for attackers. Over the last years, they suffered from exploits costing millions of dollars due to simple programming mistakes. As a result, a variety of tools for detecting bugs have been proposed. Most of these tools rely on symbolic execution, which may yield false positives due to over-approximation. Recently, many fuzzers have been proposed to detect bugs in smart contracts. However, these tend to be more effective in finding shallow bugs and less effective in finding bugs that lie deep in the execution, therefore achieving low code coverage and many false negatives. An alternative that has proven to achieve good results in traditional programs is hybrid fuzzing, a combination of symbolic execution and fuzzing. In this work, we study hybrid fuzzing on smart contracts and present ConFuzzius, the first hybrid fuzzer for smart contracts. ConFuzzius uses evolutionary fuzzing to exercise shallow parts of a smart contract and constraint solving to generate inputs that satisfy complex conditions that prevent evolutionary fuzzing from exploring deeper parts. Moreover, ConFuzzius leverages dynamic data dependency analysis to efficiently generate sequences of transactions that are more likely to result in contract states in which bugs may be hidden. We evaluate the effectiveness of ConFuzzius by comparing it with state-of-the-art symbolic execution tools and fuzzers for smart contracts. Our evaluation on a curated dataset of 128 contracts and a dataset of 21K real-world contracts shows that our hybrid approach detects more bugs than state-of-the-art tools (up to 23%) and that it outperforms existing tools in terms of code coverage (up to 69%). We also demonstrate that data dependency analysis can boost bug detection up to 18%. [less ▲]

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See detailNumerical study on design rules for minimum degree of shear connection in propped steel-concrete composite beams
Vigneri, Valentino; Odenbreit, Christoph UL; Romero, Alfredo UL

in Engineering Structures (2021), 241

This manuscript presents a numerical study on simply supported propped composite beams with ductile shear connectors subjected to uniformly distributed load. The aim is to assess the performance of the ... [more ▼]

This manuscript presents a numerical study on simply supported propped composite beams with ductile shear connectors subjected to uniformly distributed load. The aim is to assess the performance of the revised rules for the minimum degree of shear connection (CEN/TC250/SC4.T3) with respect to the occurring slip. First, a non-linear 3D finite element model was developed through the software ABAQUS 2017 and validated against analytical values of the elastic stiffness and plastic bending resistance. Then, 91 configurations were analysed for different degrees of shear connection η=0.2,0.4…1.0. The span ranges from 6 to 25 m while the geometrical and mechanical properties varied within their typical field of applicability. According to both current and revised rules, 16 configurations with relatively deep beam and “weak” concrete slab exhibited allowable slip values smax significantly higher than 6 m. Therefore, the authors proposed a reduction of the maximum degree of utilization to these special cases. If the proposed reduction is included in the revised rules, none of the considered cases exhibit a slip smax higher than 8 mm while few cases have smax between 6 and 8 mm. For the ease of use, a design proposal is reformulated as a conditional reduction of the plastic bending resistance of the composite section. [less ▲]

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See detailSimulation of gas-dynamic, pressure surges and adiabatic compression phenomena in geometrically complex respirator oxygen valves
Obeidat, Anas UL; Andreas, Thomas; Bordas, Stéphane UL et al

in Thermal Science and Engineering Progress (2021), 24

Gas-dynamic pressure surges and adiabatic compression phenomena are generally hard to predict numerically. In this contribution, we study the effect of the pressure reserve capacity on the compressible ... [more ▼]

Gas-dynamic pressure surges and adiabatic compression phenomena are generally hard to predict numerically. In this contribution, we study the effect of the pressure reserve capacity on the compressible gas-dynamics pressure surge and adiabatic compression in a fitted respirator oxygen valve geometry. A three-dimensional remeshed smoothed particle hydrodynamics method for the simulation of isotropic turbulence is used, the method is coupled with Brinkman penalisation technique for flow simulation inside the complex valve geometry. Simulations are carried out for three different pressure reserve quantities, to replicate the opening of the valve, two time-based pressure inlet boundary condition functions were simulated along with an impulsively started scenario. A geometrical sensitivity analysis is provided, where the simulation is performed on a modified valve design which exhibits a damping effect on the gas dynamics and flow characteristics, which has a favourable effect on the valve functionality and safety. It is found that the capacity of the pressure reserve has a considerable effect on the simulated flow fields (velocity, temperature), as the temperature could rise 6.0X the reference temperature, and up to 2.7X the reference velocity. The numerical results are compared with a previous study carried out by Rotarex S.A., demonstrating that the remeshed particle-mesh method coupled with Brinkman penalisation provides a good quality simulation and the results are in agreement with the reference solution. [less ▲]

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See detailNo more Piecemeal Tactics
Kafteranis, Dimitrios UL; Robert, Brochhaus

E-print/Working paper (2021)

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See detailA hyper-reduction method using adaptivity to cut the assembly costs of reduced order models
Hale, Jack UL; Schenone, Elisa; Baroli, Davide UL et al

in Computer Methods in Applied Mechanics and Engineering (2021), 380

At every iteration or timestep of the online phase of some reduced-order modelling schemes, large linear systems must be assembled and then projected onto a reduced order basis of small dimension. The ... [more ▼]

At every iteration or timestep of the online phase of some reduced-order modelling schemes, large linear systems must be assembled and then projected onto a reduced order basis of small dimension. The projected small linear systems are cheap to solve, but assembly and projection are now the dominant computational cost. In this paper we introduce a new hyper-reduction strategy called reduced assembly (RA) that drastically cuts these costs. RA consists of a triangulation adaptation algorithm that uses a local error indicator to con- struct a reduced assembly triangulation specially suited to the reduced order basis. Crucially, this reduced assembly triangulation has fewer cells than the original one, resulting in lower assembly and projection costs. We demonstrate the efficacy of RA on a Galerkin-POD type reduced order model (RAPOD). We show performance increases of up to five times over the baseline Galerkin-POD method on a non-linear reaction-diffusion problem solved with a semi-implicit time-stepping scheme and up to seven times for a 3D hyperelasticity problem solved with a continuation Newton-Raphson algorithm. The examples are implemented in the DOLFIN finite element solver using PETSc and SLEPc for linear algebra. Full code and data files to produce the results in this paper are provided as supplementary material. [less ▲]

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See detailFeasibility of ERA5 integrated water vapor trends for climate change analysis in continental Europe: An evaluation with GPS (1994–2019) by considering statistical significance
Yuan, Peng; Hunegnaw, Addisu UL; Alshawaf, Fadwa et al

in Remote Sensing of Environment (2021), 260(112416),

Although the statistical significances for the trends of integrated water vapor (IWV) are essential for a correct interpretation of climate change signals, obtaining accurate IWV trend estimates with ... [more ▼]

Although the statistical significances for the trends of integrated water vapor (IWV) are essential for a correct interpretation of climate change signals, obtaining accurate IWV trend estimates with realistic uncertainties remains a challenge. This study evaluates the feasibility of the IWV trends derived from the newly released fifth generation European Centre for Medium-Range Weather Forecasts (ECMWF) atmospheric reanalysis (ERA5) for climate change analysis in continental Europe. This is achieved by comparing the trends derived from in-situ ground-based Global Positioning System (GPS)’s daily IWV series from 1994 to 2019 at 109 stations. The realistic uncertainties and statistical significances of the IWV trends are evaluated with the time series analysis on their noise characteristics and proper noise models. Results show that autoregressive moving average ARMA(1,1) noise model is preferred rather than the commonly assumed white noise (WN) or first-order autoregressive AR(1) noise for about 68% of the ERA5 and GPS IWV series. An improper noise model would misevaluate the trend uncertainty of an IWV time series, compared with its specific preferred noise model. For example, ARMA(1,1) may misevaluate the standard deviations of their trend estimates (0.1–0.3 kg m−2 decade−1) by 10%. Nevertheless, ARMA(1,1) is recommended as the default noise model for the ERA5 and GPS IWV series. However, the preferred noise model for each ERA5 minus GPS (E-G) IWV series should be specifically determined, because the AR(1)-related models can result in an underestimation on its trend uncertainty by 90%. In contrast, power-law (PL) model can lead to an overestimation by up to nine times. The E-G IWV trends are within −0.2–0.4 kg m−2 decade−1, indicating that the ERA5 is a potential data source of IWV trends for climate change analysis in continental Europe. The ERA5 and GPS IWV trends are consistent in their magnitudes and geographical patterns, lower in Northwest Europe (0–0.4 kg m−2 decade−1) but higher around the Mediterranean Sea (0.6–1.4 kg m−2 decade−1). [less ▲]

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See detailKnowledge assessment with concept maps: Opportunities and challenges
Rohles, Björn UL; Koenig, Vincent UL; Fischbach, Antoine UL et al

Scientific Conference (2021, July)

21st-century digital society poses tremendous challenges for education and assessment. Learners have to understand the complex relations between diverse topics and learn how to learn their entire lives ... [more ▼]

21st-century digital society poses tremendous challenges for education and assessment. Learners have to understand the complex relations between diverse topics and learn how to learn their entire lives. Concept mapping is a promising approach to address these issues. It is a method that uses concepts connected by labeled links to visualize a semantic network of knowledge. Concept mapping is predestined for a digital approach because it allows for easy interactive editing, innovative test items, and incorporation of multimodal information. Concept mapping is available for summative and formative assessment and, thus, provides the opportunity to become a vital part of modern education. The biggest advantage of concept mapping (i.e., a comprehensive and yet comprehensible visualization of complex relations) also represents the biggest challenge when it comes to assessment with - and scoring of - concept maps. The first challenge is the enormous amount of indicators used for scoring concept maps in assessment. A second challenge comes from the fact that educators using concept mapping in their assessment have to understand and interpret the indicators that are used in scoring concept maps. This presentation reports on a Ph.D. project that investigates digital concept mapping in the context of knowledge assessment from a user experience perspective. The results are based on, first, a comprehensive international systematic literature review on concept map scoring, and second, three empirical studies covering the needs and experiences of learners and educators in concept mapping. It presents key findings from the iterative user experience design of a concept mapping tool as part of the online assessment platform OASYS, an overview of indicators used in concept map scoring, and research opportunities in knowledge assessment with concept maps. Finally, it stresses the value that user experience design brings to knowledge assessment with concept maps. [less ▲]

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See detailMeasuring multicultural ideology: Scale development and validation in different languages and contexts
Stogianni, Maria UL; Schmidt, Lea Marie; Murdock, Elke UL et al

Scientific Conference (2021, July)

Increased migration has led to the formation of culturally diverse societies in many places around the world. The concept of Multicultural Ideology incorporates two values as a way to promote positive ... [more ▼]

Increased migration has led to the formation of culturally diverse societies in many places around the world. The concept of Multicultural Ideology incorporates two values as a way to promote positive intercultural relations: a) Diversity: the presence of ethnocultural diversity in the population and b) Equity: the right for equal participation of all cultural groups in the society. Both diversity and equity are necessary conditions for the success of multicultural policies. Culturally heterogeneous communities that do not support inclusion and equitable participation of all groups face the negative consequences of segregation and marginalization. In line with this notion, an international research consortium is developing a revised version of the Multicultural Ideology Scale to assess the endorsement of multicultural ideology in different national contexts. The scale aims to distinguish various attitudinal dimensions of multiculturalism, relevant to the acceptance of diversity and social inclusion of different ethnocultural groups: Cultural Maintenance, Social Interaction, Equity/Inclusion, Extent of Differences, Conflictual Relations, Essentialistic Boundaries. We present the first assessment of the new scale in the German language. The survey was administered online to a sample of native German citizens (N = 382) with different demographic characteristics. Our aim was to understand the attitude of native citizens towards cultural diversity and their willingness to have members of ethnic minority groups be included in the larger society. We investigated the factor structure of the scale, its psychometric properties, and the relationship between multicultural ideology and some individual difference variables, such as ethnic group attachment and social dominance orientation. [less ▲]

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See detailRESIF 3.0: Toward a Flexible & Automated Management of User Software Environment on HPC facility
Varrette, Sébastien UL; Kieffer, Emmanuel UL; Pinel, Frederic UL et al

in ACM Practice and Experience in Advanced Research Computing (PEARC'21) (2021, July)

HPC is increasingly identified as a strategic asset and enabler to accelerate the research and the business performed in all areas requiring intensive computing and large-scale Big Data analytic ... [more ▼]

HPC is increasingly identified as a strategic asset and enabler to accelerate the research and the business performed in all areas requiring intensive computing and large-scale Big Data analytic capabilities. The efficient exploitation of heterogeneous computing resources featuring different processor architectures and generations, coupled with the eventual presence of GPU accelerators, remains a challenge. The University of Luxembourg operates since 2007 a large academic HPC facility which remains one of the reference implementation within the country and offers a cutting-edge research infrastructure to Luxembourg public research. The HPC support team invests a significant amount of time in providing a software environment optimised for hundreds of users, but the complexity of HPC software was quickly outpacing the capabilities of classical software management tools. Since 2014, our scientific software stack is generated and deployed in an automated and consistent way through the RESIF framework, a wrapper on top of Easybuild and Lmod meant to efficiently handle user software generation. A large code refactoring was performed in 2017 to better handle different software sets and roles across multiple clusters, all piloted through a dedicated control repository. With the advent in 2020 of a new supercomputer featuring a different CPU architecture, and to mitigate the identified limitations of the existing framework, we report in this state-of-practice article RESIF 3.0, the latest iteration of our scientific software management suit now relying on streamline Easybuild. It permitted to reduce by around 90% the number of custom configurations previously enforced by specific Slurm and MPI settings, while sustaining optimised builds coexisting for different dimensions of CPU and GPU architectures. The workflow for contributing back to the Easybuild community was also automated and a current work in progress aims at drastically decrease the building time of a complete software set generation. Overall, most design choices for our wrapper have been motivated by several years of experience in addressing in a flexible and convenient way the heterogeneous needs inherent to an academic environment aiming for research excellence. As the code base is available publicly, and as we wish to transparently report also the pitfalls and difficulties met, this tool may thus help other HPC centres to consolidate their own software management stack. [less ▲]

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See detailSmall in size, great in significance: conspicilla and perspicilla in the visual arts of the Low Countries around 1600
Koeleman, Floor UL

Scientific Conference (2021, July)

A largely forgotten constcamer painting from the early seventeenth century shows eyeglasses and a telescope in close proximity. The inclusion of these extensions of sight in The Five Senses of the Musée ... [more ▼]

A largely forgotten constcamer painting from the early seventeenth century shows eyeglasses and a telescope in close proximity. The inclusion of these extensions of sight in The Five Senses of the Musée Magnin (Dijon) seems to allude to the implicit link between the two. As tools to observe with and through, these instruments visualize the limits of human perception and the ability to alter the scale of the visible world. The Five Senses was created in Antwerp around the same time the telescope first appeared in textual sources, namely 1608. However, the optical instrument is likely to have existed for years by then. This paper investigates if any references to the telescope in the visual arts predate the first written evidence of its invention. For artists the early telescope was probably not that challenging an object to represent. The exterior, a simple tube characterized by a diaphragm, housed two lenses made by the same glass industry that manufactured eyeglasses. This paper takes a closer look at the imagery of eyeglasses and telescopes, depicted in the visual arts of the late sixteenth and early seventeenth centuries. The meaning assigned to these instruments can be inferred from the context in which they are presented and their relative scale. Together eyeglasses and telescopes feature prominently in constcamer paintings dedicated to visual perception, understood both physically and metaphysically. While the exact date of creation remains subject to debate, The Five Senses probably contains the earliest known depiction of a telescope – true to scale. [less ▲]

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See detailLuxembourg
Leist, Anja UL

in Immergut, E.; Anderson, K.; Devitt, C. (Eds.) et al Health politics in Europe: A handbook (2021)

Detailed reference viewed: 86 (11 UL)