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See detailTHz-Empowered UAVs in 6G: Opportunities, Challenges, and Trade-Offs
Azari, Mohammad Mahdi UL; Solanki, Sourabh UL; Chatzinotas, Symeon UL et al

in IEEE Communications Magazine (in press)

Envisioned use cases of unmanned aerial vehicles (UAVs) impose new service requirements in terms of data rate, latency, and sensing accuracy, to name a few. If such requirements are satisfactorily met, it ... [more ▼]

Envisioned use cases of unmanned aerial vehicles (UAVs) impose new service requirements in terms of data rate, latency, and sensing accuracy, to name a few. If such requirements are satisfactorily met, it can create novel applications and enable highly reliable and harmonized integration of UAVs in the 6G network ecosystem. Towards this, terahertz (THz) bands are perceived as a prospective technological enabler for various improved functionalities such as ultra-high throughput and enhanced sensing capabilities. This paper focuses on THz-empowered UAVs with the following capabilities: communication, sensing, localization, imaging, and control. We review the potential opportunities and use cases of THz-empowered UAVs, corresponding novel design challenges, and resulting trade-offs. Furthermore, we overview recent advances in UAV deployments regulations, THz standardization, and health aspects related to THz bands. Finally, we take UAV to UAV (U2U) communication as a case-study to provide numerical insights into the impact of various system design parameters and environment factors. [less ▲]

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See detailZur Wechselseitigkeit von Sozialer Anerkennung und Selbstbildung: Jugendliche und junge Erwachsene im Alter zwischen 12 und 30 Jahren in Einrichtungen der Jugendarbeit
Biewers, Sandra UL; Weis, Daniel UL; Latz, Anita UL

in Baltes-Löhr, Christel; Schumacher, Anette; Biewers, Sandra (Eds.) Zufriedenheit - Wohlbefinden - Anerkennung. Ein Blick hinter die Kulissen non-formaler Bildungseinrichtungen in Luxemburg (in press)

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See detailSelf-education – Recognition – Well-being. Insights into a mixed-methods-research on the value of non-formal education in the adolescence. Abstract.
Biewers, Sandra UL; Weis, Daniel UL; Latz, Anita UL

in Carmo, Mafalda (Ed.) Education and New Developments - Book of Abstracts (in press)

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See detailFedFog: Network-Aware Optimization of Federated Learning over Wireless Fog-Cloud System
Nguyen, van Dinh UL; Chatzinotas, Symeon UL; Ottersten, Björn UL et al

in IEEE Transactions on Wireless Communications (in press)

Federated learning (FL) is capable of performing large distributed machine learning tasks across multiple edge users by periodically aggregating trained local parameters. To address key challenges of ... [more ▼]

Federated learning (FL) is capable of performing large distributed machine learning tasks across multiple edge users by periodically aggregating trained local parameters. To address key challenges of enabling FL over a wireless fogcloud system (e.g., non-i.i.d. data, users’ heterogeneity), we first propose an efficient FL algorithm based on Federated Averaging (called FedFog) to perform the local aggregation of gradient parameters at fog servers and global training update at the cloud. Next, we employ FedFog in wireless fog-cloud systems by investigating a novel network-aware FL optimization problem that strikes the balance between the global loss and completion time. An iterative algorithm is then developed to obtain a precise measurement of the system performance, which helps design an efficient stopping criteria to output an appropriate number of global rounds. To mitigate the straggler effect, we propose a flexible user aggregation strategy that trains fast users first to obtain a certain level of accuracy before allowing slow users to join the global training updates. Extensive numerical results using several real-world FL tasks are provided to verify the theoretical convergence of FedFog. We also show that the proposed co-design of FL and communication is essential to substantially improve resource utilization while achieving comparable accuracy of the learning model. [less ▲]

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See detailOptimal Priority Assignment for Real-Time Systems: A Coevolution-Based Approach
Lee, Jaekwon UL; Shin, Seung Yeob UL; Nejati, Shiva et al

in Emperical Software Engineering (in press)

In real-time systems, priorities assigned to real-time tasks determine the order of task executions, by relying on an underlying task scheduling policy. Assigning optimal priority values to tasks is ... [more ▼]

In real-time systems, priorities assigned to real-time tasks determine the order of task executions, by relying on an underlying task scheduling policy. Assigning optimal priority values to tasks is critical to allow the tasks to complete their executions while maximizing safety margins from their specified deadlines. This enables real-time systems to tolerate unexpected overheads in task executions and still meet their deadlines. In practice, priority assignments result from an interactive process between the development and testing teams. In this article, we propose an automated method that aims to identify the best possible priority assignments in real-time systems, accounting for multiple objectives regarding safety margins and engineering constraints. Our approach is based on a multi-objective, competitive coevolutionary algorithm mimicking the interactive priority assignment process between the development and testing teams. We evaluate our approach by applying it to six industrial systems from different domains and several synthetic systems. The results indicate that our approach significantly outperforms both our baselines, i.e., random search and sequential search, and solutions defined by practitioners. Our approach scales to complex industrial systems as an offline analysis method that attempts to find near-optimal solutions within acceptable time, i.e., less than 16 hours. [less ▲]

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See detailEnergy performance comparison of ventilation-based heating versus water-based heating systems in an efficient residential building
Shirani, Arsalan UL; Merzkirch, Alexander; Leyer, Stephan UL et al

in Fluid Dynamics & Material Processing (in press)

The application of air-based heating systems as a possible approach to reduce the construction costs in highly efficient residential buildings is becoming popular. Air-based heating systems have been well ... [more ▼]

The application of air-based heating systems as a possible approach to reduce the construction costs in highly efficient residential buildings is becoming popular. Air-based heating systems have been well-known for their usage in passive houses during the past three decades. Available studies on such systems tend mostly to focus only on comparing exhaust air heat pump technology with conventional systems in efficient buildings. Moreover, most of the existing studies ignore the usual presence of the electrical heaters as backup. Besides, a comprehensive study and comparison between different air-based heating system concepts is still missing. In this study, four different air-based heating system concepts separated by the type of heat source of heat pump for heating and domestic hot water are defined. These systems are compared to four conventional heating system, including floor heating and direct electrical system employing dynamic annual simulations. According to simulation results, the systems with floor heating have shown the best system efficiencies and the lowest energy demand in comparison to the other systems. The main reason for this was the lower supply temperatures of the floor heating systems. Between the air heating systems, the system equipped with an outdoor air heat pump showed a better energy performance than an exhaust air system. The main reason for this could be attributed to the power limitation of exhaust air heat pump systems. [less ▲]

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See detailProtéger, libérer, assujettir. L’extension territoriale de la commune de Florence au XIVe siècle
Abeles, Solal UL

Book published by École française de Rome (in press)

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See detailSprachliche Mittel in Fake News: Eine textlinguistische Perspektive
Huemer, Birgit UL

in Bendheim, Amelie; Pavlik, Jennifer (Eds.) Fake News. Von Fakten und Fiktionen in Literatur und Medien (in press)

Linguistische Studien zum Thema Fake News nähern sich diesem Phänomen hauptsächlich aus zwei verschiedenen Richtungen. Mit Methoden der kritischen Diskursanalyse wird untersucht wie der Begriff Fake News ... [more ▼]

Linguistische Studien zum Thema Fake News nähern sich diesem Phänomen hauptsächlich aus zwei verschiedenen Richtungen. Mit Methoden der kritischen Diskursanalyse wird untersucht wie der Begriff Fake News im öffentlichen Diskurs verwendet wird, welche Vorstellungen geschaffen, welche Identitäten konstruiert werden und welche Machtverhältnisse erzeugt, verteidigt oder herausgefordert werden. Computerlinguistische Ansätze beschäftigen sich mit der Charakterisierung und automatisierten Erkennung von Fake News, um diese von sogenanntem „rechtmäßigen“ Nachrichten (legitimate news ) zu unterscheiden. Textlinguistische Untersuchungen zum Thema Fake News gibt es bisher kaum. In diesem Beitrag wird zuerst den wenig vorhandenen linguistischen Definitionsansätzen von Fake News auf den Grund gegangen, mit dem Ziel diese durch die textlinguistische Analyse zu ergänzen. Danach werden die beiden sprachwissenschaftlichen Zugänge zum Phänomen Fake News vorgestellt und einige Untersuchungen zum Corona-Diskurs skizziert, die für die Beispielanalyse relevant sind. Exemplarisch werden in der vorliegenden Untersuchung redaktionelle Beiträge und Fake News zum Corona-Diskurs qualitative analysiert und miteinander verglichen. Damit wird der Versuch unternommen Fake News als Textsorte einzuordnen und die sprachlichen Strategien herauszuarbeiten, die für dieses Phänomen typisch sind. Die zuvor erwähnten linguistischen Zugänge liefern dabei wertvolle Ergebnisse, die als Ausgangsbasis für diese Untersuchung dienen. Die Analyse zeigt, dass sich Fake News zwar an journalistischen Nachrichtenformaten orientieren, jedoch sprachliche Muster aufweisen, die sie von diesen unterscheiden. Unter anderem benutzen sie sprachliche Strategien wie Polarisierung, starke Wertungen und direkte Leseradressierung, die für redaktionelle Berichterstattung unüblich ist. Diese Strategien sind nicht nur für Fake News typisch, sondern weisen eine gewisse Parallele zu sprachlichen Mustern in Verschwörungstheorien und Propaganda auf. [less ▲]

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See detailA Machine Learning Approach for Automated Filling of Categorical Fields in Data Entry Forms
Belgacem, Hichem UL; Li, Xiaochen; Bianculli, Domenico UL et al

in ACM Transactions on Software Engineering and Methodology (in press)

Users frequently interact with software systems through data entry forms. However, form filling is time-consuming and error-prone. Although several techniques have been proposed to auto-complete or pre ... [more ▼]

Users frequently interact with software systems through data entry forms. However, form filling is time-consuming and error-prone. Although several techniques have been proposed to auto-complete or pre-fill fields in the forms, they provide limited support to help users fill categorical fields, i.e., fields that require users to choose the right value among a large set of options. In this paper, we propose LAFF, a learning-based automated approach for filling categorical fields in data entry forms. LAFF first builds Bayesian Network models by learning field dependencies from a set of historical input instances, representing the values of the fields that have been filled in the past. To improve its learning ability, LAFF uses local modeling to effectively mine the local dependencies of fields in a cluster of input instances. During the form filling phase, LAFF uses such models to predict possible values of a target field, based on the values in the already-filled fields of the form and their dependencies; the predicted values (endorsed based on field dependencies and prediction confidence) are then provided to the end-user as a list of suggestions. We evaluated LAFF by assessing its effectiveness and efficiency in form filling on two datasets, one of them proprietary from the banking domain. Experimental results show that LAFF is able to provide accurate suggestions with a Mean Reciprocal Rank value above 0.73. Furthermore, LAFF is efficient, requiring at most 317 ms per suggestion. [less ▲]

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See detailEmpirical risk assessment of maintenance costs under full-service contracts
Deprez, Laurens UL; Antonio, Katrien; Boute, Robert

in European Journal of Operational Research (in press)

We provide a data-driven framework to conduct a risk assessment, including data pre-processing, exploration, and statistical modeling, on a portfolio of full-service maintenance contracts. These contracts ... [more ▼]

We provide a data-driven framework to conduct a risk assessment, including data pre-processing, exploration, and statistical modeling, on a portfolio of full-service maintenance contracts. These contracts cover all maintenance-related costs for a fixed, upfront fee during a predetermined horizon. Charging each contract a price proportional to its risk prevents adverse selection by incentivizing low risk (i.e., maintenance-light) profiles to not renege on their agreements. We borrow techniques from non-life insurance pricing and tailor them to the setting of maintenance contracts to assess the risk and estimate the expected maintenance costs under a full-service contract. We apply the framework on a portfolio of about 5 000 full-service contracts of industrial equipment and show how a data-driven analysis based on contract and machine characteristics, or risk factors, supports a differentiated, risk-based break-even tariff plan. We employ generalized additive models (GAMs) to predict the risk factors’ impact on the frequency (number of) and severity (cost) of maintenance interventions. GAMs are interpretable yet flexible statistical models that capture the effect of both continuous and categorical risk factors. Our predictive models quantify the impact of the contract and machine type, service history, and machine running hours on the contract cost. We additionally utilize the predictive cost distributions of our models to augment the break-even price with the appropriate risk margins to further protect against the inherently stochastic nature of the maintenance costs. The framework shows how maintenance intervention data can set up a differentiated tariff plan. [less ▲]

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See detailIntercorrelated random fields with bounds and the Bayesian identification of their parameters: Application to linear elastic struts and fibers
Rappel, Hussein; Girolami, Mark; Beex, Lars UL

in International Journal for Numerical Methods in Engineering (in press)

Many materials and structures consist of numerous slender struts or fibers. Due to the manufacturing processes of different types of struts and the growth processes of natural fibers, their mechanical ... [more ▼]

Many materials and structures consist of numerous slender struts or fibers. Due to the manufacturing processes of different types of struts and the growth processes of natural fibers, their mechanical response frequently fluctuates from strut to strut, as well as locally within each strut. In associated mechanical models each strut is often represented by a string of beam elements, since the use of conventional three-dimensional finite elements renders the simulations computationally inefficient. The parameter input fields of each string of beam elements are ideally such that the local fluctuations and fluctuations between individual strings of beam elements are accurately captured. The goal of this study is to capture these fluctuations in several intercorrelated bounded random fields. Two formulations to describe the intercorrelations between each random field, as well as the case without any intercorrelation, are investigated. As only a few sets of input fields are available (due to time constraints of the supposed experimental techniques), the identification of the random fields’ parameters involves substantial uncertainties. A probabilistic identification approach based on Bayes’ theorem is employed to treat the involved uncertainties. [less ▲]

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See detailCOVID-19 and the global venture capital landscape
Bellavitis, Cristiano; Fisch, Christian UL; McNaughton, Rod

in Small Business Economics (in press)

We assess the effect of the COVID-19 pandemic on venture capital (VC) investments, documenting a significant decline in investments using a dataset of 39,527 funding rounds occurring before and during the ... [more ▼]

We assess the effect of the COVID-19 pandemic on venture capital (VC) investments, documenting a significant decline in investments using a dataset of 39,527 funding rounds occurring before and during the pandemic in 130 countries. In line with our theoretical considerations, we show that this decline is more pronounced for investments characterized by higher uncertainty, namely investments in seed-stage ventures, industries affected more heavily by the COVID-19 crisis, international investments, and non-syndicated investments. Investor prominence partially moderates these effects. [less ▲]

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See detailCorporate Managers, Price Noise and the Investment Factor
Lehnert, Thorsten UL

in Financial Innovation (2022)

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See detailBetting Against Noisy Beta
Lehnert, Thorsten UL

in Journal of Finance and Data Science (2022), 8(-), 55-68

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See detailAustralian Indigenous Life Writing: Analysing Discourses with Word Embedding Modelling
Kamlovskaya, Ekaterina UL

Doctoral thesis (2022)

The genre of Australian Aboriginal autobiography is a literature of significant socio-political importance, with authors sharing a history different to the one previously asserted by the European settlers ... [more ▼]

The genre of Australian Aboriginal autobiography is a literature of significant socio-political importance, with authors sharing a history different to the one previously asserted by the European settlers which ignored or misrepresented Australia's First People. While there has been a number of studies looking at the works belonging to this genre from various perspectives, Australian Indigenous life writing has never been approached from the digital humanities point of view which, given the constant development of computer technologies and growing availability of digital sources, offers humanities researchers many opportunities for exploring textual collections from various angles. With this research work I contribute to closing the above-mentioned research gap and discuss the results of the interdisciplinary research project within the scope of which I created a bibliography of published Australian Indigenous life writing works, designed and assembled a corpus and created word embedding models of this corpus which I then used to explore the discourses of identity, land, sport, and foodways, as well as gender biases present in the texts in the context of postcolonial literary studies and Australian history. Studying these discourses is crucial for gaining a better understanding of the contemporary Australian society as well as the nation's history. Word embeddings modelling has recently been used in digital humanities as an exploratory technique to complement and guide traditional close reading approaches, which is justified by their potential to identify word use patterns in a collection of texts. In this dissertation, I provide a case study of how word embedding modelling can be used to investigate humanities research questions and reflect on the issues which researchers may face while working with such models, approaching various aspects of the research project from the perspectives of digital source and tool criticism. I demonstrate how word embedding model of the analysed corpus represents discourses through relationships between word vectors that reflect the historical, political, and cultural environment of the authors and some unique experiences and perspectives related to their racial and gender identities. I show how the narrators reconstruct the analysed discourses to achieve the main goals of Australian Indigenous life writing as a genre - reclaiming identity and rewriting history. [less ▲]

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See detailThe Aesthetics of Smoke in Interwar Luxembourgish Literature
Millim, Anne-Marie UL

Presentation (2022, October 19)

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See detailParallel Multi-Physics Simulation of Biomass Furnace and Cloud-based Workflow for SMEs
Besseron, Xavier UL; Rusche, Henrik; Peters, Bernhard UL

in Practice and Experience in Advanced Research Computing (PEARC '22) (2022, July)

Biomass combustion is a well-established process to produce energy that offers a credible alternative to reduce the consumption of fossil fuel. To optimize the process of biomass combustion, numerical ... [more ▼]

Biomass combustion is a well-established process to produce energy that offers a credible alternative to reduce the consumption of fossil fuel. To optimize the process of biomass combustion, numerical simulation is a less expensive and time-effective approach than the experimental method. However, biomass combustion involves intricate physical phenomena that must be modeled (and validated) carefully, in the fuel bed and in the surrounding gas. With this level of complexity, these simulations require the use of High-Performance Computing (HPC) platforms and expertise, which are usually not affordable for manufacturing SMEs. In this work, we developed a parallel simulation tool for the simulation of biomass furnaces that relies on a parallel coupling between Computation Fluid Dynamics (CFD) and Discrete Element Method (DEM). This approach is computation-intensive but provides accurate and detailed results for biomass combustion with a moving fuel bed. Our implementation combines FOAM-extend (for the gas phase) parallelized with MPI, and XDEM (for the solid particles) parallelized with OpenMP, to take advantage of HPC hardware. We also carry out a thorough performance evaluation of our implementation using an industrial biomass furnace setup. Additionally, we present a fully automated workflow that handles all steps from the user input to the analysis of the results. Hundreds of parameters can be modified, including the furnace geometry and fuel settings. The workflow prepares the simulation input, delegates the computing-intensive simulation to an HPC platform, and collects the results. Our solution is integrated into the Digital Marketplace of the CloudiFacturing EU project and is directly available to SMEs via a Cloud portal. As a result, we provide a cutting-edge simulation of a biomass furnace running on HPC. With this tool, we demonstrate how HPC can benefit engineering and manufacturing SMEs, and empower them to compute and solve problems that cannot be tackled without. [less ▲]

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See detailArea-Power Analysis of FFT Based Digital Beamforming for GEO, MEO, and LEO Scenarios
Palisetty, Rakesh UL; Eappen, Geoffrey UL; Gonzalez Rios, Jorge Luis UL et al

Scientific Conference (2022, June 19)

Satellite communication systems can provide seamless wireless coverage directly or through complementary ground terrestrial components and are projected to be incorporated into future wireless networks ... [more ▼]

Satellite communication systems can provide seamless wireless coverage directly or through complementary ground terrestrial components and are projected to be incorporated into future wireless networks, particularly 5G and beyond networks. Increased capacity and flexibility in telecom satellite payloads based on classic radio frequency technology have traditionally translated into increased power consumption and dissipation. Much of the analog hardware in a satellite communications payload can be replaced with highly integrated digital components that are often smaller, lighter, and less expensive, as well as software reprogrammable. Digital beamforming of thousands of beams simultaneously is not practical due to the limited power available onboard satellite processors. Reduced digital beamforming power consumption would enable the deployment of a full digital payload, resulting in comprehensive user applications. Beamforming can be implemented using matrix multiplication, hybrid methodology, or a discrete Fourier transform (DFT). Implementing DFT via fast Fourier transform (FFT) reduces the power consumption, process time, hardware requirements, and chip area. Therefore, in this paper, area-power efficient FFT architectures for digital beamforming are analyzed. The area in terms of look up tables (LUTs) is estimated and compared among conventional FFT, fully unrolled FFT, and a 4-bit quantized twiddle factor (TF) FFT. Further, for the typical satellite scenarios, area, and power estimation are reported. [less ▲]

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