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See detailMobility policy through the lens of policy mobility: The post-political case of introducing free transit in Luxembourg
Carr, Constance UL; Hesse, Markus UL

in Journal of Transport Geography (2020), 83

This viewpoint paper addresses the issue of fare-free public transport (FFPT) in the context of policy mobility, the strand of urban studies literature that examines how policy formulations developed in ... [more ▼]

This viewpoint paper addresses the issue of fare-free public transport (FFPT) in the context of policy mobility, the strand of urban studies literature that examines how policy formulations developed in one place tend to ‘travel’ and inform and inspire plans elsewhere as good or best practices. We argue that the promotion of policies may not reflect a serious attempt to solve a sustainability or socio-economic issue. Rather, the institutions in charge have different targets in mind. FFPT in Luxembourg is thus more a reflection of a post-political process where politics are severed from the political. [less ▲]

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See detailPerceptions of Society’s Necessary Standard of Living: Are Perceptions Determined by What People Have, or Do They Reflect a Social Consensus?
Gutfleisch, Tamara Rebecca UL; Andreß, Hans-Jürgen

in Social Indicators Research (2020)

Analyses of material deprivation usually use lists of goods and activities to assess an individual’s possessions and to compare it with the society’s standard of living. If the number of possessions falls ... [more ▼]

Analyses of material deprivation usually use lists of goods and activities to assess an individual’s possessions and to compare it with the society’s standard of living. If the number of possessions falls below a certain threshold, the individual is assumed to be materially deprived. Also state-guaranteed minimum income payments are often based on a basket of goods, which are assumed to represent a minimal living standard in the respective society. However, this approach rests on the assumption that a social consensus exists about what constitutes society’s necessary standard of living, which has never been tested in a theoretically and methodologically sound way. Our paper provides a model of the main determinants of standard of living perceptions in the public, develops a measurement model for a survey of necessary items, and tests whether these perceptions are expressions of a consensual normative standard or reflections of the respondent’s idiosyncratic individual living situation. We have used two waves of the GESIS Panel in 2016 to survey the current opinions about the necessary standard of living in the German population. Estimating cross-lagged auto-correlated structural equation models, we find that necessity evaluations are quite homogeneous across social groups but are influenced by individuals’ possessions, which vary within society and hence, challenge the social consensus assumption. Moreover, instead of using only the most necessary items, survey instruments should include both necessary and less necessary items to reflect the whole distribution of possible standard of living perceptions. Our results further suggest that analyses using single items should be avoided due to possible measurement errors. [less ▲]

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See detailDeep dive into Interledger: Understanding the Ripple ecosystem - Part 4
Trestioreanu, Lucian Andrei UL; Cassagnes, Cyril UL; State, Radu UL

Learning material (2020)

At the technical level, the goal of Interledger is to provide an architecture and a minimal set of protocols to enable interoperability for any value transfer system. The Interledger protocol is literally ... [more ▼]

At the technical level, the goal of Interledger is to provide an architecture and a minimal set of protocols to enable interoperability for any value transfer system. The Interledger protocol is literally a protocol for interledger payments. To understand how is it possible to achieve this goal, several aspects of the technology require a deeper analysis. For this reason, in our journey to become knowledgeable and active contributor we decided to create our own test-bed on our premises. By doing so, we noticed that some aspects are well documented but we found that others might need more attention and clarification. Despite a large community effort, the task to keep information on a fast evolving software ecosystem is tedious and not always the priority for such a project. Therefore, the purpose of this document is to guide, through several hands-on activities, community members who want to engage at different levels. The document consolidates all the relevant information from generating a simple payment to ultimately create a test-bed with the Interledger protocol suite between Ripple and other distributed ledger technology. [less ▲]

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See detailThe ALMA-Yactul Ecosystem: A Holistic Approach for Student-centered Integration of Learning Material
Grevisse, Christian UL

Doctoral thesis (2020)

Digital learning resources play a key role in technology enhanced learning, yet their organization poses a challenge to both learners and teachers. Students are confronted with an ever-growing amount of ... [more ▼]

Digital learning resources play a key role in technology enhanced learning, yet their organization poses a challenge to both learners and teachers. Students are confronted with an ever-growing amount of available resources in an open, heterogeneous corpus. Finding relevant learning material for a given context or task, such as an exercise, is non-trivial, especially for novices in a complex domain, who often lack specific search skills. In addition, there is often no direct link between the learning material and the task at hand, and the constant interruption of the task in order to search for resources may have an impact on the cognitive load. Moreover, from the perspective of teachers and instructional designers, authoring high-quality learning material is a time-intensive task. Hence, reusing the authored material in multiple contexts would be beneficial. This dissertation addresses these issues by proposing the ALMA-Yactul ecosystem, a holistic approach for student-centered integration of learning material. Learners can benefit from scaffolding support to retrieve learning material relevant to their current context at a fine-grained level and across the boundaries of individual courses. This integration is showcased in multiple applications and domains, such as a plugin for an Integrated Development Environment or an enhanced sketchnoting app. While the former provides novices in computer programming the necessary tools to scaffold the search for heterogeneous documents on fine-grained syntactical elements, the latter allows for suggesting further information while taking notes in class. In both cases, it is not necessary for learners to leave their current study environment. To implicitly link learning resources and tasks, Semantic Web technologies such as ontologies are used to annotate documents. For this purpose, an extensible and lightweight modular domain ontology for programming languages has been created. While the main study domain in this work is computer science with a special focus on programming, the transferability of the proposed approach to other domains is demonstrated through multiple examples. Furthermore, to foster the active engagement of students in the learning process, Yactul, a game-based platform for continuous active learning has been developed. Apart from its use in the classroom, the platform also provides formative assessment to the individual learner by keeping track of her performance on a per-concept basis. Yactul activities are a key element in the ecosystem, both benefitting from and contributing to the integration of learning material. Finally, teachers are assisted in semantically enhancing their resources through semi-automatic annotation support within popular authoring tools. A Knowledge Graph-based approach is employed for core concept identification. Apart from analysing the usage of this ecosystem and evaluating the user satisfaction in university courses, an experiment with high school pupils lacking prior knowledge in programming yielded positive results with respect to the proposed scaffolding support. [less ▲]

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See detailDie Landwirtschaft in der Provinz Gallia Narbonensis und die Frage nach dem Sozialstatus der Arbeitskräfte
Groff, Thierry UL

in Frankfurter elektronische Rundschau zur Altertumskunde (2020), 39(2019), 1-12

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See detailMagnetic Guinier law
Michels, Andreas UL; Malyeyev, Artem UL; Titov, Ivan UL et al

in IUCrJ (2020), 7

Small-angle scattering of x-rays and neutrons is a routine method for the determination of nanoparticle sizes. The so-called Guinier law represents the low-q approximation for the small-angle scattering ... [more ▼]

Small-angle scattering of x-rays and neutrons is a routine method for the determination of nanoparticle sizes. The so-called Guinier law represents the low-q approximation for the small-angle scattering curve from an assembly of particles. The Guinier law has originally been derived for nonmagnetic particle-matrix-type systems, and it is successfully employed for the estimation of particle sizes in various scientific domains (e.g., soft matter physics, biology, colloidal chemistry, materials science). An important prerequisite for it to apply is the presence of a discontinuous interface separating particles and matrix. Here, we introduce the Guinier law for the case of magnetic small-angle neutron scattering (SANS) and experimentally demonstrate its applicability for the example of nanocrystalline cobalt. It is well- known that the magnetic microstructure of nanocrystalline ferromagnets is highly nonuniform on the nanometer length scale and characterized by a spectrum of continuously varying long-wavelength magnetization fluctuations, i.e., these systems do not manifest sharp interfaces in their magnetization profile. The magnetic Guinier radius depends on the applied magnetic field, on the magnetic interactions (exchange, magnetostatics), and on the magnetic anisotropy-field radius, which characterizes the size over which the magnetic anisotropy field is coherently aligned into the same direction. In contrast to the nonmagnetic conventional Guinier law, the magnetic version can be applied to fully dense random-anisotropy-type ferromagnets. [less ▲]

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See detailThe Potential Short- and Long-Term Disruptions and Transformative Impacts of 5G and Beyond Wireless Networks: Lessons Learnt from the Development of a 5G Testbed Environment
PATWARY, MOHMAMMAD; NAWAZ, SYED JUNAID; RAHMAN, MD. ABDUR et al

in IEEE Access (2020)

The capacity and coverage requirements for 5th generation (5G) and beyond wireless connectivity will be significantly different from the predecessor networks. To meet these requirements, the anticipated ... [more ▼]

The capacity and coverage requirements for 5th generation (5G) and beyond wireless connectivity will be significantly different from the predecessor networks. To meet these requirements, the anticipated deployment cost in the United Kingdom (UK) is predicted to be between £30bn and £50bn, whereas the current annual capital expenditure (CapEX) of the mobile network operators (MNOs) is £2.5bn. This prospect has vastly impacted and has become one of the major delaying factors for building the 5G physical infrastructure, whereas other areas of 5G are progressing at their speed. Due to the expensive and complicated nature of the network infrastructure and spectrum, the second-tier operators, widely known as mobile virtual network operators (MVNO), are entirely dependent on the MNOs. In this paper, an extensive study is conducted to explore the possibilities of reducing the 5G deployment cost and developing viable business models. In this regard, the potential of infrastructure, data, and spectrum sharing is thoroughly investigated. It is established that the use of existing public infrastructure (e.g., streetlights, telephone poles, etc.) has a potential to reduce the anticipated cost by about 40% to 60%. This paper also reviews the recent Ofcom initiatives to release location-based licenses of the 5G-compatible radio spectrum. Our study suggests that simplification of infrastructure and spectrum will encourage the exponential growth of scenario-specific cellular networks (e.g., private networks, community networks, micro-operators) and will potentially disrupt the current business models of telecommunication business stakeholders – specifically MNOs and TowerCos. Furthermore, the anticipated dense device connectivity in 5G will increase the resolution of traditional and non-traditional data availability significantly. This will encourage extensive data harvesting as a business opportunity and function within small and medium-sized enterprises (SMEs) as well as large social networks. Consequently, the rise of new infrastructures and spectrum stakeholders is anticipated. This will fuel the development of a 5G data exchange ecosystem where data transactions are deemed to be high-value business commodities. The privacy and security of such data, as well as definitions of the associated revenue models and ownership, are challenging areas – and these have yet to emerge and mature fully. In this direction, this paper proposes the development of a unified data hub with layered structured privacy and security along with blockchain and encrypted off-chain based ownership/royalty tracking. Also, a data economy-oriented business model is proposed. The study found that with the potential commodification of data and data transactions along with the low-cost physical infrastructure and spectrum, the 5G network will introduce significant disruption in the Telco business ecosystem. [less ▲]

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See detailSoft law, effectiveness of fundamental rights and migration: how effective are migrants’ fundamental rights in an era of European governance
Mavrouli, Roila UL

in Current Challenges in Migration Policy and Law, Edited by Emília Lana de Freitas Castro and Sergio Maia Tavares, Published in London, England, ISBN: 978-1-910781-77-7 (2020)

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See detailKatrin Becker, Was tun Sie?
Becker, Katrin UL

in forum für Politik, Gesellschaft und Kultur (2020), 402

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

Diverse speeches and writings (2020)

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See detailClarifying the Role of Negative Emotions in the Origin and Control of Impulsive Actions.
Eben, Charlotte; Billieux, Joël UL; Verbruggen, Frederick

in Psychologica Belgica (2020), 60(1), 1-17

This critical review elaborates on the origin of impulsive actions and how these can be controlled. We focus in particular on the role of negative events. First, we outline how impulsive actions often ... [more ▼]

This critical review elaborates on the origin of impulsive actions and how these can be controlled. We focus in particular on the role of negative events. First, we outline how impulsive actions often originate from negative events that are (emotionally) appraised. A discrepancy between this current state and a desired goal state leads to action tendencies. The urgency of the resulting action depends on the importance of the goal and the size of the discrepancy. Second, we discuss how such impulsive actions can be regulated or controlled e.g. by biasing competition between different options, or by completely suppressing all motor output. Importantly, such control mechanisms might also depend on emotional factors. To reconcile these findings, we present a coherent theoretical framework, taking into account various cognitive, affective, and motivational mechanisms as well as contextual factors that play a crucial role in the origin and control of impulsive actions. [less ▲]

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See detailModeling and Implementation of 5G Edge Caching over Satellite
Vu, Thang Xuan UL; Poirier, Yannick; Chatzinotas, Symeon UL et al

in International Journal of Satellite Communications and Networking (2020)

The fifth generation (5G) wireless networks have to deal with the high data rate and stringent latency requirements due to the massive invasion of connected devices and data-hungry applications. Edge ... [more ▼]

The fifth generation (5G) wireless networks have to deal with the high data rate and stringent latency requirements due to the massive invasion of connected devices and data-hungry applications. Edge caching is a promising technique to overcome these challenges by prefetching the content closer to the end users at the edge node’s local storage. In this paper, we analyze the performance of edge caching 5G networks with the aid of satellite communication systems. Firstly, we investigate the satellite-aided edge caching systems in two promising use cases: a) in dense urban areas, and b) in sparsely populated regions, e.g., rural areas. Secondly, we study the effectiveness of satellite systems via the proposed satellite-aided caching algorithm, which can be used in three configurations: i) mono-beam satellite, ii) multi-beam satellite, and iii) hybrid mode. Thirdly, the proposed caching algorithm is evaluated by using both empirical Zipf-distribution data and the more realistic Movielens dataset. Last but not least, the proposed caching scheme is implemented and tested by our developed demonstrators which allow real-time analysis of the cache hit ratio and cost analysis. [less ▲]

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See detailUnderstanding the Evolution of Android App Vulnerabilities
Gao, Jun UL; li, li; Bissyande, Tegawendé François D Assise UL et al

in IEEE Transactions on Reliability (2020)

The Android ecosystem today is a growing universe of a few billion devices, hundreds of millions of users and millions of applications targeting a wide range of activities where sensitive information is ... [more ▼]

The Android ecosystem today is a growing universe of a few billion devices, hundreds of millions of users and millions of applications targeting a wide range of activities where sensitive information is collected and processed. Security of communication and privacy of data are thus of utmost importance in application development. Yet, regularly, there are reports of successful attacks targeting Android users. While some of those attacks exploit vulnerabilities in the Android OS, others directly concern application-level code written by a large pool of developers with varying experience. Recently, a number of studies have investigated this phenomenon, focusing however only on a specific vulnerability type appearing in apps, and based on only a snapshot of the situation at a given time. Thus, the community is still lacking comprehensive studies exploring how vulnerabilities have evolved over time, and how they evolve in a single app across developer updates. Our work fills this gap by leveraging a data stream of 5 million app packages to re-construct versioned lineages of Android apps and finally obtained 28;564 app lineages (i.e., successive releases of the same Android apps) with more than 10 app versions each, corresponding to a total of 465;037 apks. Based on these app lineages, we apply state-of- the-art vulnerability-finding tools and investigate systematically the reports produced by each tool. In particular, we study which types of vulnerabilities are found, how they are introduced in the app code, where they are located, and whether they foreshadow malware. We provide insights based on the quantitative data as reported by the tools, but we further discuss the potential false positives. Our findings and study artifacts constitute a tangible knowledge to the community. It could be leveraged by developers to focus verification tasks, and by researchers to drive vulnerability discovery and repair research efforts. [less ▲]

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See detailApproximation-Refinement Testing of Compute-Intensive Cyber-Physical Models: An Approach Based on System Identification
Menghi, Claudio UL; Nejati, Shiva UL; Briand, Lionel UL et al

in Proceedings of the 42st International Conference on Software Engineering (2020)

Black-box testing has been extensively applied to test models of Cyber-Physical systems (CPS) since these models are not often amenable to static and symbolic testing and verification. Black-box testing ... [more ▼]

Black-box testing has been extensively applied to test models of Cyber-Physical systems (CPS) since these models are not often amenable to static and symbolic testing and verification. Black-box testing, however, requires to execute the model under test for a large number of candidate test inputs. This poses a challenge for a large and practically-important category of CPS models, known as compute-intensive CPS (CI-CPS) models, where a single simulation may take hours to complete. We propose a novel approach, namely ARIsTEO, to enable effective and efficient testing of CI-CPS models. Our approach embeds black-box testing into an iterative approximation-refinement loop. At the start, some sampled inputs and outputs of the CI-CPS model under test are used to generate a surrogate model that is faster to execute and can be subjected to black-box testing. Any failure-revealing test identified for the surrogate model is checked on the original model. If spurious, the test results are used to refine the surrogate model to be tested again. Otherwise, the test reveals a valid failure. We evaluated ARIsTEO by comparing it with S-Taliro, an open-source and industry-strength tool for testing CPS models. Our results, obtained based on five publicly-available CPS models, show that, on average, ARIsTEO is able to find 24% more requirements violations than S-Taliro and is 31% faster than S-Taliro in finding those violations. We further assessed the effectiveness and efficiency of ARIsTEO on a large industrial case study from the satellite domain. In contrast to S-Taliro, ARIsTEO successfully tested two different versions of this model and could identify three requirements violations, requiring four hours, on average, for each violation. [less ▲]

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See detailAttribute evaluation on attack trees with incomplete information
Buldas, Ahto; Gadyatskaya, Olga UL; Lenin, Aleksandr et al

in Computers and Security (2020), 88(101630),

Attack trees are considered a useful tool for security modelling because they support qualitative as well as quantitative analysis. The quantitative approach is based on values associated to each node in ... [more ▼]

Attack trees are considered a useful tool for security modelling because they support qualitative as well as quantitative analysis. The quantitative approach is based on values associated to each node in the tree, expressing, for instance, the minimal cost or probability of an attack. Current quantitative methods for attack trees allow the analyst to, based on an initial assignment of values to the leaf nodes, derive the values of the higher nodes in the tree. In practice, however, it shows to be very difficult to obtain reliable values for all leaf nodes. The main reasons are that data is only available for some of the nodes, that data is available for intermediate nodes rather than for the leaf nodes, or even that the available data is inconsistent. We address these problems by developing a generalisation of the standard bottom-up calculation method in three ways. First, we allow initial attributions of non-leaf nodes. Second, we admit additional relations between attack steps beyond those provided by the underlying attack tree semantics. Third, we support the calculation of an approximative solution in case of inconsistencies. We illustrate our method, which is based on constraint programming, by a comprehensive case study. [less ▲]

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See detailNouvelles perspectives sur les maternités. Regards croisés des Sciences et de la littérature
Barthelmebs, Hélène UL; Raguin, Marjolaine

Book published by Peter Lang (2020)

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See detailNormal approximation for functions of hidden Markov models
Kerchev, George UL

E-print/Working paper (2020)

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See detailIntegrating Topological Proofs with Model Checking to Instrument Iterative Design
Menghi, Claudio UL; Rizzi, Alessandro Maria; Bernasconi, Anna

in Proceedings of the 23rd International Conference on Fundamental Approaches to Software Engineering, FASE 2020 (2020)

System development is not a linear, one-shot process. It proceeds through refinements and revisions. To support assurance that the system satisfies its requirements, it is desirable that continuous ... [more ▼]

System development is not a linear, one-shot process. It proceeds through refinements and revisions. To support assurance that the system satisfies its requirements, it is desirable that continuous verification can be performed after each refinement or revision step. To achieve practical adoption, formal verification must accommodate continuous verification efficiently and effectively. Model checking provides developers with information useful to improve their models only when a property is not satisfied, i.e., when a counterexample is returned. However, it is desirable to have some useful information also when a property is instead satisfied. To address this problem we propose TOrPEDO, an approach that supports verification in two complementary forms: model checking and proofs. While model checking is typically used to pinpoint model behaviors that violate requirements, proofs can instead explain why requirements are satisfied. In our work, we introduce a specific notion of proof, called Topological Proof. A topological proof produces a slice of the original model that justifies the property satisfaction. Because models can be incomplete, TOrPEDO supports reasoning on requirements satisfaction, violation, and possible satisfaction (in the case where satisfaction depends on unknown parts of the model). Evaluation is performed by checking how topological proofs support software development on 12 modeling scenarios and 15 different properties obtained from 3 examples from literature. Results show that: (i) topological proofs are ≈60% smaller than the original models; (ii) after a revision, in ≈78% of cases, the property can be re-verified by relying on a simple syntactic check. [less ▲]

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See detailCortisol rapidly increases baroreflex sensitivity of heart rate control, but does not affect cardiac modulation of startle
Schulz, André UL; Richter, Steffen; Ferreira de Sá, Diana S. et al

in Physiology and Behavior (2020), 215(1), 112792

Cortisol, the final product of human HPA axis activation, rapidly modulates the cortical processing of afferent signals originating from the cardiovascular system. While peripheral effects have been ... [more ▼]

Cortisol, the final product of human HPA axis activation, rapidly modulates the cortical processing of afferent signals originating from the cardiovascular system. While peripheral effects have been excluded, it remains unclear whether this effect is mediated by cortical or subcortical (e.g. brainstem) CNS mechanisms. Cardiac modulation of startle (CMS) has been proposed as a method to reflect cardio-afferent signals at subcortical (potentially brainstem-) level. Using a single blind, randomized controlled design, the cortisol group (n = 16 volunteers) received 1 mg cortisol intravenously, while the control group (n = 16) received a placebo substance. The CMS procedure involved the assessment of eye blink responses to acoustic startle stimuli elicited at six different latencies to ECG-recorded R-waves (R + 0, 100, 200, 300, 400 and 500 ms). CMS was assessed at four measurement points: baseline, -16 min, +0 min, and +16 min relative to substance application. Baroreflex sensitivity (BRS) of heart rate (HR) control was measured non-invasively based on spontaneous beat-to-beat HR and systolic blood pressure changes. In the cortisol group, salivary cortisol concentration increased after IV cortisol administration, indicating effective distribution of the substance throughout the body. Furthermore, BRS increased in the cortisol group after cortisol infusion. There was no effect of cortisol on the CMS effect, however. These results suggest that low doses of cortisol do not affect baro-afferent signals, but central or efferent components of the arterial baroreflex circuit presumably via rapid, non-genomic mechanisms. [less ▲]

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