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See detailA Cybersecurity Incident: Who You Gonna Call?
Schmitz, Sandra UL

Scientific Conference (2022, May 25)

Detailed reference viewed: 27 (1 UL)
See detailThe NIS 2.0 Directive - Lessons learnt or lagging behind? A legal perspective
Schmitz, Sandra UL

Scientific Conference (2022, May 10)

Detailed reference viewed: 75 (0 UL)
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See detailThe need of standardised metadata to encode causal relationships: Towards safer data-driven machine learning biological solutions
Garcia Santa Cruz, Beatriz UL; Vega Moreno, Carlos Gonzalo UL; Hertel, Frank UL

Scientific Conference (2021, November 16)

In this paper, we discuss the importance of considering causal relations in the development of machine learning solutions to prevent factors hampering the robustness and generalisation capacity of the ... [more ▼]

In this paper, we discuss the importance of considering causal relations in the development of machine learning solutions to prevent factors hampering the robustness and generalisation capacity of the models, such as induced biases. This issue often arises when the algorithm decision is affected by confounding factors. In this work, we argue that the integration of causal relationships can identify potential confounders. We call for standardised meta-information practices as a crucial step for proper machine learning solutions development, validation, and data sharing. Such practices include detailing the dataset generation process, aiming for automatic integration of causal relationships. [less ▲]

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See detailAWJC Nozzle simulation by 6-way coupling of DEM+CFD+FEM using preCICE coupling library
Adhav, Prasad UL; Besseron, Xavier UL; ROUSSET, Alban et al

Scientific Conference (2021, June 16)

The objective of this work is to study the particle-laden fluid-structure interaction within an Abrasive Water Jet Cutting Nozzle. Such coupling is needed to study the erosion phenomena caused by the ... [more ▼]

The objective of this work is to study the particle-laden fluid-structure interaction within an Abrasive Water Jet Cutting Nozzle. Such coupling is needed to study the erosion phenomena caused by the abrasive particles inside the nozzle. So far, the erosion in the nozzle was predicted only through the number of collisions, using only a simple DEM+CFD[1] coupling. To improve these predictions, we extend our model to a 6-way Eulerian-Lagrangian momentum coupling with DEM+CFD+FEM to account for deformations and vibrations in the nozzle. Our prototype uses the preCICE coupling library[2] to couple 3 numerical solvers: XDEM[3] (for the particle motion), OpenFOAM[4] (for the water jet), and CalculiX[5] (for the nozzle deformation). XDEM handles all the particle motions based on the fluid properties and flow conditions, and it calculates drag terms. In the fluid solver, particles are modeled as drag and are injected in the momentum equation as a source term. CalculiX uses the forces coming from the fluid solver and XDEM as boundary conditions to solve for the displacements. It is also used for computing the vibrations induced by particle impacts. . The preliminary 6-way DEM+CFD+FEM coupled simulation is able to capture the complex particle-laden multiphase fluid-structure interaction inside AWJC Nozzle. The erosion concentration zones are identified and are compared to DEM+CFD coupling[1]. The results obtained are planned to be used for predicting erosion intensity in addition to the concentration zones. In the future, we aim to compare the erosions predictions to experimental data in order to evaluate the suitability of our approach. The FEM module of the coupled simulation captures the vibration frequency induced by particles and compares it with the natural frequency of the nozzle. Thus opening up opportunities for further investigation and improvement of the Nozzle design. [less ▲]

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See detailReliability of network-wide traffic management
Rinaldi, Marco; Viti, Francesco UL

Scientific Conference (2021, June)

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See detailApplying synchronization in branch and trunk bus networks: an experimental analysis
Laskaris, Georgios; Rinaldi, Marco; Viti, Francesco UL

Scientific Conference (2021, June)

Detailed reference viewed: 23 (1 UL)
Peer Reviewed
See detailAn equilibrium model for Mobility-as-a-Service
Bandiera, Claudia UL; Connors, Richard UL; Viti, Francesco UL

Scientific Conference (2021, May)

Detailed reference viewed: 40 (6 UL)
Peer Reviewed
See detailConsiderations on Dynamic Pricing in Carsharing Operations
Giorgione, Giulio UL; Viti, Francesco UL

Scientific Conference (2021, May)

Detailed reference viewed: 35 (4 UL)
Peer Reviewed
See detailOffice Agents: Personal Office Vitality Sensors with Intent
Stamhuis, Sjoerd; Brombacher, Hans; Vos, Steven et al

Scientific Conference (2021, May)

In smart office buildings, almost every aspect of the environment can be assessed and adjusted by sensors. Yet employees rarely have access to the data collected to act upon it. It is also unclear what ... [more ▼]

In smart office buildings, almost every aspect of the environment can be assessed and adjusted by sensors. Yet employees rarely have access to the data collected to act upon it. It is also unclear what they would find meaningful to follow the recommendations on healthy work conditions and behavior, while productivity is the priority. The Office Agents are a set of artefacts placed on the employee’s desk, which capture data about the office environment. Air quality, sound level, light exposure, productivity, and physical activity level are measured to provide office workers with feedback on the ‘best’ working conditions. Using speculative design and Objects with Intent, the employee engages in a negotiation with the Office Agents based on the office ecosystem. Through this project and interactivity session, we open a debate on the use of sensors in office environments and the stakes around office vitality from the viewpoint of the employees. [less ▲]

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See detaildolfiny: Convenience wrappers for DOLFINx
Zilian, Andreas UL; Habera, Michal UL

Scientific Conference (2021, March 23)

With the increased flexibility of DOLFINx and its reduction to core functionality, the responsibility for even some basic components of computational analysis is shifted to the user. This presentation ... [more ▼]

With the increased flexibility of DOLFINx and its reduction to core functionality, the responsibility for even some basic components of computational analysis is shifted to the user. This presentation provides an overview of the open-source package dolfiny, which provides end-user API interfaces to mesh/meshtags generation and processing, expression list handling, function interpolation and projection as well as the restriction of function spaces to parts of the computational domain. This functionality is consistently considered in interfaces to PETSc/SNES as nonlinear solver and SLEPc as eigensolver backend, both allowing the operation on block and nested operators. In addition, the package provides a convenient approach to incorporate time integration into the UFL formulation of the problem, which is exemplified for the generalised alpha method. The capability of dolfiny is demonstrated in a number of examples, ranging between finite strain structural analysis, plasticity and fluid-structure interaction. [less ▲]

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See detailA Markov Chain Monte Carlo Approach for Estimating Daily Activity Patterns
Scheffer, Ariane Hélène Marie UL; Bandiera, Claudia UL; Cipriani, Ernesto et al

Scientific Conference (2021, February)

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See detailSensitivity Analysis on Regularity Based Driver Advisory Systems
Laskaris, Georgios; Seredynski, Marcin; Viti, Francesco UL

Scientific Conference (2021, February)

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See detailInvestigating heuristic algorithms for minimal controller location set problem in transportation networks
Mazur, Xavier UL; Rinaldi, Marco; Viti, Francesco UL

Scientific Conference (2021, February)

Detailed reference viewed: 18 (4 UL)
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See detailHPC Multi-physics Biomass Furnace simulations as a Service
Besseron, Xavier UL; Rusche, Henrik; Peters, Bernhard UL et al

Scientific Conference (2020, November)

Detailed reference viewed: 98 (7 UL)
See detailSTREAMS: A supporting tool for shared mobility services
Giorgione, Giulio UL; Viti, Francesco UL

Scientific Conference (2020, November)

Detailed reference viewed: 95 (5 UL)
See detaileCoBus: Smart and sustainable public transport in Luxembourg
Viti, Francesco UL

Scientific Conference (2020, November)

Detailed reference viewed: 82 (4 UL)
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See detailActive Popularity Learning with Cache Hit Ratio Guarantees using a Matrix Completion Committee
Bommaraveni, Srikanth UL; Vu, Thang Xuan UL; Chatzinotas, Symeon UL et al

Scientific Conference (2020, October 08)

Edge caching is a promising technology to facethe stringent latency requirements and back-haul trafficoverloading in 5G wireless networks. However, acquiringthe contents and modeling the optimal cache ... [more ▼]

Edge caching is a promising technology to facethe stringent latency requirements and back-haul trafficoverloading in 5G wireless networks. However, acquiringthe contents and modeling the optimal cache strategy is achallenging task. In this work, we use an active learningapproach to learn the content popularities since it allowsthe system to leverage the trade-off between explorationand exploitation. Exploration refers to caching new fileswhereas exploitation use known files to cache, to achievea good cache hit ratio. In this paper, we mainly focus tolearn popularities as fast as possible while guaranteeing anoperational cache hit ratio constraint. The effectiveness ofproposed learning and caching policies are demonstratedvia simulation results as a function of variance, cache hitratio and used storage. [less ▲]

Detailed reference viewed: 70 (4 UL)
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See detailDigitizing of Research and Teaching
Plapper, Peter UL

Scientific Conference (2020, September 05)

The current Covid-19 crisis impacts all manufacturing areas and new processes are sought. This presentation provides the audience with three examples related to assembly work instructions, logistics data ... [more ▼]

The current Covid-19 crisis impacts all manufacturing areas and new processes are sought. This presentation provides the audience with three examples related to assembly work instructions, logistics data handling and manufacturing education, for which innovative ways to obtain access to context sensitive data based on digital tools are investigated. Augmented Reality (AR) and Virtual Reality (VR) facilitate access to relevant manufacturing information. In order to provide logistic warehouse workers with immediate access to shipping documents, to avoid paper print-outs, and to eliminate error-prone typing of information, critical information should be handled digitally and hands-free. To support logistic workers to efficiently document, register and trace receipt, storage or delivery of goods, the presented solution is built on hands-free digital tools with AR technology in commercially available smart glasses. Similarly, workers who execute complex assembly operations frequently require either assistance or support for the next assembly step. Depending on the context, relevant assembly process information is automatically displayed together with the environment in the AR smart glass. Thus, the operator is supported by the presented hands-free-tool to complete the next challenging tasks. Currently, teaching is being transferred from physical class-room teaching to remote or hybrid education. For this purpose, Virtual Reality (VR) provides a very welcome opportunity to complement in-presence teaching with exposure to examples of real manufacturing operations captured in videos of industrial case studies. Students apply learnings from theoretical classes to manufacturing case studies by identifying best practices and also recognizing waste. The presentation shares experience in teaching of lean methods based on AR technology to graduate engineering students. [less ▲]

Detailed reference viewed: 91 (5 UL)
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See detailA short Survey on the Cyber Security in Control Systems
Bezzaoucha, Souad UL; Voos, Holger UL

Scientific Conference (2020, July)

In the present survey paper, we give a short, yet exhaustive state-of-the-art about the cyber-security applied to control systems, especially the event-based strategy. Indeed, in the past few years, due ... [more ▼]

In the present survey paper, we give a short, yet exhaustive state-of-the-art about the cyber-security applied to control systems, especially the event-based strategy. Indeed, in the past few years, due to a highest degree of connectivity in modern systems, new related control-specific cyber-physical systems security challengesarise and novel approaches integrating the cyber aspect are developed.Our goal in this paper is then to provide an overview of attack-modeling and security analysis approaches in recent works thatexplore networked control systems subject to cyber-attacks attacks. To this end, we look at the control, estimation, and modeling problems. [less ▲]

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See detailDATA DRIVEN SURGICAL SIMULATIONS
Deshpande, Saurabh UL; Bordas, Stéphane UL; Beex, Lars UL et al

Scientific Conference (2020, July)

Detailed reference viewed: 117 (15 UL)
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See detailConventional EO Satellites vs. CubeSats; FDL - AI flood detection onboard a Nano Satellite
Backes, Dietmar UL; Schumann, Guy; Teferle, Felix Norman UL

Scientific Conference (2019, December 11)

Detailed reference viewed: 67 (2 UL)
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See detailParameter identification problem in bimaterial human skin and sensitivity analysis : Uncertainties in biomechanics of skin
Sutula, Danas; Elouneg, Aflah; Sensale, Marco UL et al

Scientific Conference (2019, December 09)

The proposed paper concerns the prediction of the numerical response of a biomechanical structure submitted to an unknown external loading state. The methodology is based on homogeneous and then ... [more ▼]

The proposed paper concerns the prediction of the numerical response of a biomechanical structure submitted to an unknown external loading state. The methodology is based on homogeneous and then heterogeneous structures such as healthy or pathological cutaneous tissues that can be mechanically tested in vivo under a patchy knowledge of boundary conditions. Experimental data corresponding to the extension of a piece of skin located between two pads with displacement enslavement, represent input data to the numerical model. Data are reaction force on one pad and displacement field between the two pads and all around. The numerical model consists of a representation of the bi-material domain geometry with neo-hookean behaviors. The boundary conditions and loadings of the experimental extension test are imposed. The materials parameters have been identified by inverse method starting from a constrained cost function minimizing the difference between the calculated displacements field and experimental displacements field obtained by digital image correlation and taking into account the reaction force as a constraint. An analysis of the model sensitivity to material parameters is presented. [less ▲]

Detailed reference viewed: 37 (0 UL)
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See detailMechanical parameters identification of keloid and surrounding healthy skin using Digital Image Correlation measurements in vivo
Elouneg, Aflah; Sutula, Danas; Sensale, Marco UL et al

Scientific Conference (2019, December 09)

The human skin behaves as an elastic membrane initially prestressed but not uniformly. The presence of anatomical sites favorable to the appearance of some tumors, a keloid in our case, while other sites ... [more ▼]

The human skin behaves as an elastic membrane initially prestressed but not uniformly. The presence of anatomical sites favorable to the appearance of some tumors, a keloid in our case, while other sites never develop them attests to the importance of the mechanical environment of the tissue. Thus, a mechanical characterization of the tumored skin is necessary to understand the keloid expansion from a mechanical point of view. Our case study consists in modeling a bi-material structure composed of a keloid skin surrounded by healthy skin located on upper left arm of a young female. From the experimental measurements in vivo, by combining force sensor, displacement sensor and Digital Image Correlation techniques, we perform a mechanical analysis to characterize the mechanical stress fields over the entire area and on the interface ‘healthy skin/keloid skin’. Since the mechanical behavior of the tumorous skin is unknown, many physical models can be implemented and assessed very easily inside the specific digital software to fit with the real data. Once a set of mechanical parameters for both the healthy skin and the keloid skin are identified, the stress fields around the keloid are calculated. Next steps consist in determining matching preferential directions in order to define as precisely as possible the specifications of a device for preventing the growth of keloids. [less ▲]

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See detailActive Content Popularity Learning via Query-by-Committee for Edge Caching
Bommaraveni, Srikanth UL; Vu, Thang; Vuppala, Satyanarayana et al

Scientific Conference (2019, November 03)

Edge caching has received much attention as an effective solution to face the stringent latency requirements in 5G networks due to the proliferation of handset devices as well as data-hungry applications ... [more ▼]

Edge caching has received much attention as an effective solution to face the stringent latency requirements in 5G networks due to the proliferation of handset devices as well as data-hungry applications. One of the challenges in edge caching systems is to optimally cache strategic contents to maximize the percentage of total requests served by the edge caches. To enable the optimal caching strategy, we propose an Active Learning approach (AL) to learn and design an accurate content request prediction algorithm. Specifically, we use an AL based Query-by-committee (QBC) matrix completion algorithm with a strategy of querying the most informative missing entries of the content popularity matrix. The proposed AL framework leverage's the trade-off between exploration and exploitation of the network, and learn the user's preferences by posing queries or recommendations. Later, it exploits the known information to maximize the system performance. The effectiveness of proposed AL based QBC content learning algorithm is demonstrated via numerical results. [less ▲]

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See detailTowards Dynamic Zero Emission Zone Management for Plug-in Hybrid Buses
Seredynski, Marcin UL; Viti, Francesco UL

Scientific Conference (2019, November)

Detailed reference viewed: 52 (8 UL)
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See detailFlood Detection On Low Cost Orbital Hardware
Mateo-Garcia, Gonzalo; Oprea, Silviu; Smith, Lewis et al

Scientific Conference (2019, October)

Satellite imaging is a critical technology for monitoring and responding to natural disasters such as flooding. Despite the capabilities of modern satellites, there is still much to be desired from the ... [more ▼]

Satellite imaging is a critical technology for monitoring and responding to natural disasters such as flooding. Despite the capabilities of modern satellites, there is still much to be desired from the perspective of first response organisations like UNICEF. Two main challenges are rapid access to data, and the ability to automatically identify flooded regions in images. We describe a prototypical flood segmentation system, identifying cloud, water and land, that could be deployed on a constellation of small satellites, performing processing on board to reduce downlink bandwidth by 2 orders of magnitude. We target PhiSat-1, part of the FSSCAT mission, which is planned to be launched by the European Space Agency (ESA) near the start of 2020 as a proof of concept for this new technology. [less ▲]

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See detailA comparison between conventional Earth Observation Satellites and CubeSats; Requirements, Capabilities and Data Quality
Backes, Dietmar UL; Hassani, Saif Alislam UL; Teferle, Felix Norman UL et al

Scientific Conference (2019, September 11)

From its early beginning as an educational tool in 1999, cubesats have evolved into a popular platform for technology demonstrations and scientific instruments. Ideas and innovations sparked from an ... [more ▼]

From its early beginning as an educational tool in 1999, cubesats have evolved into a popular platform for technology demonstrations and scientific instruments. Ideas and innovations sparked from an enthusiastic community led to the development of new Earth Observation (EO) technology concepts based on large constellations of satellites with high-resolution optical imagers previously considered as infeasible. Probably the most significant constellation today is deployed by Planet who are currently operating a fleet larger than 120 3U Dove satellites, which provide an imaging service with up to 3m Ground Sample Distance (GSD). The number of low-cost EO Cubesat systems is constantly increasing. However, for a number of reasons there still seems to be a reluctance to use such data for many EO applications. A better understanding of the capabilities of the current generation of small Cubesats compared to the traditional well-established bigger operational missions of high and medium resolution EO satellites is required. What are the critical capabilities and quality indicators? Due to the limited size and weight of Cubesats, critical system components, e.g. for navigation and communication, always compete with operational payloads such as optical camera/sensor systems. A functional EO system requires balanced payload, which provides adequate navigational capabilities, that match the requirements of the optical imagers (camera) deployed with the system. This study reviews the current performance and capabilities of Cubesats for optical EO and compares them to the capabilities of conventional, dedicated high and medium resolution EO systems. We summarise key performance parameters and quality indicators to evaluate the difference between the systems. An empirical study compares recent very high-resolution (VHR) imagery from big EO satellite missions with available images from Cubesats for the use case in disaster monitoring. Small and agile Nanosatellites or Cubesats already show remarkable performance. Although it is not expected that their performance and capability will match those of current bigger EO satellite missions, they are expected to provide a valuable tool for EO and remote sensing, in particular for downstream industry applications. [less ▲]

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See detailPrinciples for setting single line and multiline control based on network characteristics
Laskaris, Georgios UL; Cats, Oded; Jenelius, Erik et al

Scientific Conference (2019, September)

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See detailA real time hybrid controller for regulating bus operations and reducing stops at signals
Laskaris, Georgios UL; Seredynski, Marcin; Viti, Francesco UL

Scientific Conference (2019, June)

We propose a hybrid controller which consists of holding and a Driver Advisory System (DAS). It combines the objectives of seeking the regularization of operation and the reduction of stop and go actions ... [more ▼]

We propose a hybrid controller which consists of holding and a Driver Advisory System (DAS). It combines the objectives of seeking the regularization of operation and the reduction of stop and go actions at signalized intersections. A simple headway based holding criterion is applied at stops to define the time needed to maintain even spaced headways between buses and additionally a speed recommendation is given to traverse during green indication at the downstream signalized intersection. The controller is tested using simulation for a bus line of the city of Luxembourg, Luxembourg and compared to a benchmark scenario, the single application of bus holding, two advisory systems and different levels of transit signal priority. Results show that there are additional benefits compared to traditional holding in terms of regularity while similar performance to strong transit signal priority is achieved in terms of time spent at traffic lights. [less ▲]

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See detailSupply characteristics and membership choice in round-trip and free-floating carsharing systems
Cisterna, Carolina UL; Giorgione, Giulio UL; Cipriani, Ernesto et al

Scientific Conference (2019, June)

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See detailLeveraging GIS Data and Topological Information to Infer Trip Chaining Behaviour at Macroscopic Level
Carrese, Filippo; Fusco, Gaetano; Cantelmo, Guido et al

Scientific Conference (2019, June)

One of the open challenges in transport modelling is to estimate within-day demand flows that reflect the complexity of individual activity-travel behaviour. While disaggregate (Activity-Based) demand ... [more ▼]

One of the open challenges in transport modelling is to estimate within-day demand flows that reflect the complexity of individual activity-travel behaviour. While disaggregate (Activity-Based) demand models can recreate realistic daily mobility patterns at an individual level, they usually require an accurate knowledge of individual user behaviour (i.e. via travel surveys), which is not always available. As a result, practitioners often turn to aggregate demand models, that have the advantage of being less demanding in terms of data but typically under represent the demand for secondary activities. In this work, we take research on within-day demand modelling one step forward by proposing a framework that combines traditional methodologies with heterogeneous data sources in order to explicitly represent trip chaining at an aggregated level. We show that the combination of web-based crowd sensed data, network data and behavioural constraints allows to capture complex spatial and temporal correlations between demand patterns. The methodology is applied on the classical Gravity model to show how to incorporate within-day dynamics. Yet, any alternative demand model can be adopted. In our case, Generation and Attraction are used to estimate the systematic demand, that is enriched of information about individual activity patterns, and then a novel definition of impedance function based on Hagestraand ellipse theory plays a central role in spatially distributing locations of trips using geographic relationships and constraints deriving from space-time behaviour. A case study for Luxembourg City has been presented to show the potential of the methodology: the choice of using data from a different spatial context to account for the temporal dimension has been validated through comparisons with official statistics. The results of simulating a workplace relocation show the advantages of this new approach in representing demand related to secondary activities. [less ▲]

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See detailMixed hybrid and electric bus dynamic fleet management in urban networks: a model predictive control approach
Rinaldi, Marco UL; Picarelli, Erika UL; D'Ariano, Andrea et al

Scientific Conference (2019, June)

Abstract—Reducing pollutant emissions and promoting sustainable mobility solutions, including Public Transport, are increasingly becoming key objectives for policymakers worldwide. In order to jointly ... [more ▼]

Abstract—Reducing pollutant emissions and promoting sustainable mobility solutions, including Public Transport, are increasingly becoming key objectives for policymakers worldwide. In order to jointly achieve these goals, careful consideration should be put on the operational cost and management of PT services, in order to promote the adoption of green mobility solutions and advanced management techniques by operators. In this work we develop a dynamic fleet management approach for next generation Public Transportation systems, considering the instance of mixed electric / hybrid fleet. Our objective is that of investigating to what extent electrification, coupled with optimal fleet management, can yield operational cost savings for PT operators, explicitly considering real-time disturbances, including delays, service disruptions etc. We propose a Mixed Integer Linear Program to address the problem of optimal scheduling of a mixed fleet of electric and hybrid / non-electric buses, and employ it as predictor in a Model Predictive Control approach. Test results based upon a real-life scenario showcase how the proposed approach is indeed capable of yielding a sizable reduction in operational costs, even when considerable disturbances arise from the underlying system. [less ▲]

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See detailADVANCES IN GEOMETRY INDEPENDENT APPROXIMATIONS
Anitescu, Cosmin; Atroshchenko, Elena; Bordas, Stéphane UL et al

Scientific Conference (2019, April 11)

We present recent advances in geometry independent field approximations. The GIFT approach is a generalisation of isogeometric analysis where the approximation used to describe the field variables no ... [more ▼]

We present recent advances in geometry independent field approximations. The GIFT approach is a generalisation of isogeometric analysis where the approximation used to describe the field variables no-longer has to be identical to the approximation used to describe the geometry of the domain. As such, the geometry can be described using usual CAD representations, e.g. NURBS, which are the most common in the CAD area, whilst local refinement and meshes approximations can be used to describe the field variables, enabling local adaptivity. We show in which cases the approach passes the patch test and present applications to various mechanics, fracture and multi-physics problems. [less ▲]

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See detailMixed hybrid and electric bus dynamic fleet management in urban networks: a model predictive control approach
Rinaldi, Marco UL; Picarelli, Erika; Laskaris, Georgios UL et al

Scientific Conference (2019, January)

Reducing pollutant emissions and promoting sustainable mobility solutions, including Public Transport, are increasingly becoming key objectives for policymakers worldwide. In order to jointly achieve ... [more ▼]

Reducing pollutant emissions and promoting sustainable mobility solutions, including Public Transport, are increasingly becoming key objectives for policymakers worldwide. In order to jointly achieve these goals, careful consideration should be put on the operational cost and management of PT services, in order to promote the adoption of green mobility solutions and advanced management techniques by operators. In this work we develop a dynamic fleet management approach for next generation Public Transportation systems, considering the instance of mixed electric / hybrid fleet. Our objective is that of investigating to what extent electrification, coupled with optimal fleet management, can yield operational cost savings for PT operators, explicitly considering real-time disturbances, including delays, service disruptions etc. We propose a Mixed Integer Linear Program to address the problem of optimal scheduling of a mixed fleet of electric and hybrid / non-electric buses, and employ it as predictor in a Model Predictive Control approach. Test results based upon a real-life scenario showcase how the proposed approach is indeed capable of yielding a sizable reduction in operational costs, even when considerable disturbances arise from the underlying system. [less ▲]

Detailed reference viewed: 231 (10 UL)
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See detailGeometrical and material uncertainties for the mechanics of composites
Barbosa, Joaquim; Bordas, Stéphane UL; Carvalho, Andre et al

Scientific Conference (2019)

Detailed reference viewed: 133 (15 UL)
See detailMerging DEMs from VHR Optical Imagery with Drone Data - A High-resolution DEM for Tristan da Cunha
Backes, Dietmar UL; Teferle, Felix Norman UL

Scientific Conference (2018, December 12)

The extraction of high-resolution, Digital Elevation Models (DEM) from very high-resolution (VHR) optical satellite imagery, as well as low altitude drone images by Photogrammetric methods or modern ... [more ▼]

The extraction of high-resolution, Digital Elevation Models (DEM) from very high-resolution (VHR) optical satellite imagery, as well as low altitude drone images by Photogrammetric methods or modern Structure from Motion (SFM) engines, has rapidly matured. Today both data sources are representing cost-effective alternatives to dedicated airborne sensors, especially for remote and difficult to access regions. Ever-growing archives of high-resolution Satellite imagery, are providing a rich data source which covers even the most remote locations with high-resolution imagery up to 0.30m ground sample distance multiple times enabling the generation of high-resolution DEMS. Furthermore, low-cost, low weight and easy to use drones can easily be deployed in remote regions and capture limited areas with very high resolution. Dense point clouds derived from this method provide an invaluable data source to fill the gap between globally available low-resolution DEMs and highly accurate terrestrial surveys. The presented case study investigates the use of VHR archive imagery as well as low-cost drone imagery to generate high-quality DEMs using photogrammetric tools over a remote region which is difficult to access by manned airborne platforms. We highlight the potential and limitations of both data sources to provide high resolution, accurate elevation data. [less ▲]

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See detailAn Interdisciplinary Methodology to Validate Formal Representations of Legal Text Applied to the GDPR
Bartolini, Cesare UL; Lenzini, Gabriele UL; Santos, Cristiana

Scientific Conference (2018, November 12)

The modelling of a legal text into a machine-processable form, such as a list of logic formulæ, enables a semi-automatic reasoning about legal compliance but might entail some anticipation of legal ... [more ▼]

The modelling of a legal text into a machine-processable form, such as a list of logic formulæ, enables a semi-automatic reasoning about legal compliance but might entail some anticipation of legal interpretation in the modelling. The formulæ need therefore to be validated by legal experts, but it is unlikely that they are familiar with the formalism used. This calls for an interdisciplinary validation methodology to ensure that the model is legally coherent with the text it aims to represent but that could also close the communication gap between formal modellers and legal evaluators. This paper discusses such a methodology, providing an human-readable representation that preserves the formulæ's meaning but that presents them in a way that is usable by non-experts. We exemplify the methodology on a use case where Articles of the GDPR are translated in the Reified I/O logic encoded in LegalRuleML. [less ▲]

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See detailOptimal dispatching of electric and hybrid buses subject to scheduling and charging constraints
Rinaldi, Marco UL; Parisi, Federico; Laskaris, Georgios UL et al

Scientific Conference (2018, November)

We consider the problem of optimally determining the sequence of electric and hybrid buses departing from a multi-line bus terminal, considering both service constraints (schedule adherence) and energy ... [more ▼]

We consider the problem of optimally determining the sequence of electric and hybrid buses departing from a multi-line bus terminal, considering both service constraints (schedule adherence) and energy constraints (electric bus charging status, bus recharging scheduling in capacitated facilities). The problem is formulated as a Mixed Integer Linear Program, with the objective of minimizing the total operational cost for the bus lines in question. System dynamics are captured by practical sets of constraints, ranging from scheduling adherence to discharge- recharge dynamics. Individual operational costs at the bus level and at the trip level are fully parametrized, allowing for extensive sensitivity analysis. We investigate a real-life case study based on the city of Luxembourg, where two charging stations have been installed in the central station’s bus terminal. Experimental results show that, while full electrification is indeed possible, the required fleet size depends strongly on the given line(s) timetable. [less ▲]

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See detailReal time multiline holding control for networks with shared transit corridor
Laskaris, Georgios UL; Cats, Oded; Jenelius, Erik et al

Scientific Conference (2018, September 05)

Detailed reference viewed: 87 (4 UL)
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See detailDecompositions of the optimal dispatching problem of electric and electric-hybrid buses with energy constraints for Luxembourg City
Picarelli, Erika; Rinaldi, Marco UL; Viti, Francesco UL et al

Scientific Conference (2018, September)

We are a team of engineers working on a concrete project of Mobility in Luxembourg. We want to solve the problem of optimally determining the sequence of electric and hybrid electric buses, considering ... [more ▼]

We are a team of engineers working on a concrete project of Mobility in Luxembourg. We want to solve the problem of optimally determining the sequence of electric and hybrid electric buses, considering both service constraints (schedule adherence) and energy constraints (electric bus charging status, bus recharging scheduling in capacitated facilities) and at the same time ensure a high level of quality of service for the user satisfaction. The problem is formulated as a Mixed Integer Linear Program, with the objective of minimizing the total operational cost for the bus lines in question. System dynamics are captured by twenty sets of constraints, ranging from scheduling adherence to discharge-recharge dynamics. Individual operational costs at the bus level (cost of running an electric / non-electric bus per km, cost of recharging) and at the trip level (penalty due to failed schedule adherence) are fully parametrised, allowing for extensive sensitivity analysis. We investigate a real-life case study based in the city of Luxembourg, where the objective is to reach the all-electric mode for principal urban buses network. Through the model we investigate: the minimum amount of electric buses necessary to perform a day’s schedule for two currently partially electrified lines, without resorting to conventional internal combustion alternatives; the impact of electrifying two additional lines, specifically considering the trade-offs related to either adding new buses or new charging stations at the bus terminal. Finally, we studied how to best decompose the overall problem in several smaller problems, to be able to solve also realistic scenarios and using large real data sets from the Mobility Data owner of Luxembourg. We analysed and compared two kinds of decomposition: a bus line-based decomposition, and a time-based decomposition. [less ▲]

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See detailAn equation-free, nested, concurrent multiscale approach without scale-separation
Beex, Lars UL; Kerfriden, Pierre

Scientific Conference (2018, September)

Detailed reference viewed: 64 (0 UL)
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See detailControllability of transportation networks
Rinaldi, Marco UL; Viti, Francesco UL

Scientific Conference (2018, September)

Detailed reference viewed: 96 (0 UL)
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See detailA holding control strategy for diverging bus lines
Laskaris, Georgios UL; Cats, Oded; Jenelius, Erik et al

Scientific Conference (2018, July 24)

We introduce a holding criterion for network configurations with lines that operate jointly along a common corridor and then individually diverge. The proposed holding decision rule accounts for all ... [more ▼]

We introduce a holding criterion for network configurations with lines that operate jointly along a common corridor and then individually diverge. The proposed holding decision rule accounts for all different passengers groups in the overlapping segment and takes care of the transition to individual line operation. The holding rule is evaluated using simulation for different demand levels and segmentations and compared with other control schemes for a real-world network. Results show that gains in overall network performance as well as for specific passenger groups can be achieved under specific demand distributions. [less ▲]

Detailed reference viewed: 86 (6 UL)
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See detailOptimal multi-line bus dispatching at terminals with electric charging scheduling constraints
Rinaldi, Marco UL; Parisi, Federico; D'Ariano, Andrea et al

Scientific Conference (2018, July)

We consider the problem of optimally determining the sequence of electric and conventional internal combustion buses departing from a multi-line bus terminal, considering both service constraints ... [more ▼]

We consider the problem of optimally determining the sequence of electric and conventional internal combustion buses departing from a multi-line bus terminal, considering both service constraints (schedule adherence) and energy constraints (electric bus charging status, bus recharging scheduling in capacitated facilities). The problem is formulated as a Mixed Integer Linear Program, with the objective of minimizing the total operational cost for the bus lines in question. System dynamics are captured by twenty sets of constraints, ranging from scheduling adherence to discharge-recharge dynamics. Individual operational costs at the bus level (cost of running an electric / non electric bus per km, cost of recharging) and at the trip level (penalty due to failed schedule adherence) are fully parametrised, allowing for extensive sensitivity analysis. We investigate a real-life case study based in the city of Luxembourg, where two charging stations have been installed in the central station’s bus terminal. Through the model we investigate: i) the minimum amount of electric buses necessary to perform a day’s schedule for two currently partially electrified lines, without resorting to conventional internal combustion alternatives; ii) the impact of electrifying two additional lines, specifically considering the trade-offs related to either adding new buses or new charging stations at the bus terminal. [less ▲]

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See detailTowards Optimised Deployment of Electric Bus Systems with On-Route Charging using Cooperative ITS
Laskaris, Georgios UL; Seredynski, Marcin; Viti, Francesco UL

Scientific Conference (2018, July)

Detailed reference viewed: 73 (10 UL)
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See detailUsing mobile phone data for urban network state estimation
Derrmann, Thierry; Frank, Raphaël UL; Engel, Thomas UL et al

Scientific Conference (2018, June)

Detailed reference viewed: 107 (4 UL)
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See detailModelling and analysis of flow-driven energy harvesting devices and associated reduced order models
Zilian, Andreas UL; Baroli, Davide UL

Scientific Conference (2018, June)

A specific class of energy harvester devices for renewable energy resources allows conversion of ambient fluid flow energy to electrical energy via flow-induced vibrations of a piezo-ceramic composite ... [more ▼]

A specific class of energy harvester devices for renewable energy resources allows conversion of ambient fluid flow energy to electrical energy via flow-induced vibrations of a piezo-ceramic composite structure positioned in the flow field. This energy converter technology simultaneously involves the interaction of a composite structure and a surrounding fluid, the electric charge accumulated in the piezo-ceramic material and a controlling electrical circuit. In order to predict the efficiency and operational properties of such future devices and to increase their robustness and performance, a mathematical and numerical model of the complex physical system is required to allow systematic computational investigation of the involved phenomena and coupling characteristics. The presentation will discuss a monolithic modelling approach that allows simultaneous analysis of the harvester, which involves surface-coupled fluid-structure interaction, volume-coupled electro-mechanics and a controlling energy harvesting circuit. Based on a finite element discretisation of the weighted residual form of the governing equations, time- and frequency-domain analysis enables investigation of different types of structures (plate, shells) subject to exterior/interior flow with varying parameters, and attached electrical circuits with respect to the electrical power output generated. Consequently, options for parametric reduced-order modelling of flow-driven energy harvesters will be discussed. [less ▲]

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See detailLEXU II „Low Exergy Wall & Air Tempering for Building Refurbishment“
Schmidt, Christoph Wilhelm; Scholzen, Frank UL

Scientific Conference (2018, April 20)

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See detailVulnerability analysis of network observability in link flow inference problems
Rinaldi, Marco UL; Viti, Francesco UL

Scientific Conference (2018, January)

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See detailNASA-FDL Artificial Intelligence in Planetary Science; Lunar Resource Mission
Backes, Dietmar UL

Scientific Conference (2017, December 15)

Detailed reference viewed: 111 (19 UL)
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See detailCoordinating merging public transport operations using holding control strategies
Laskaris, Georgios UL; Cats, Oded; Jenelius, Erik et al

Scientific Conference (2017, September 12)

Detailed reference viewed: 46 (1 UL)
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See detailMultiscale Modelling of Damage and Fracture in Discrete Materials Using a Variational Quasicontinuum Method
Rokos, Ondrej; Peerlings, Ron; Beex, Lars UL et al

Scientific Conference (2017, September 05)

Detailed reference viewed: 55 (1 UL)
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See detailExperimental and numerical assessment of the mechanics of keloid-skin composites undergoing large deformations
Sensale, Marco UL; Chambert, Jerome; Chouly, Franz et al

Scientific Conference (2017, August)

Detailed reference viewed: 117 (14 UL)
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See detaileXtended Variational Quasicontinuum Methodology for Modelling of Crack Propagation in Discrete Lattice Systems
Rokos, Ondrej; Peerlings, Ron; Zeman, Jan et al

Scientific Conference (2017, July 17)

Detailed reference viewed: 51 (0 UL)
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See detailAn equation-free multiscale method: a result of extending the quasicontinuum method to irregular structures
Beex, Lars UL; Kerfriden, Pierre

Scientific Conference (2017, July 16)

Detailed reference viewed: 65 (2 UL)
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See detailError-controlled computational fracture mechanics
Bordas, Stéphane UL

Scientific Conference (2017, July 12)

Detailed reference viewed: 372 (33 UL)
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See detailThe effect of workplace relocation on individuals’ activity travel behaviour
Sprumont, François UL; Viti, Francesco UL

Scientific Conference (2017, July 04)

During working days, home and workplace are anchor locations shaping the daily mobility as well as the employee’s activity pattern. While past research has shown that workplace decentralization is often ... [more ▼]

During working days, home and workplace are anchor locations shaping the daily mobility as well as the employee’s activity pattern. While past research has shown that workplace decentralization is often associated with higher car use for the commuting trip, little is known concerning the effect on activity-travel patterns as whole. The objective of this paper is to assess how workplace decentralization is affecting individuals’ daily activity space. A two-weeks travel diary has been filled by 43 employees of the University of Luxembourg, both before and after the relocation of their workplace. Using descriptive statistics, as well as Standard Deviational Ellipses (SDE) combined with a cluster analysis, results of this paper show that workers’ activity spaces, represented by the Standard Deviational Ellipses, have been importantly modified due to a relocation of a single anchor activity location, i.e. their workplace [less ▲]

Detailed reference viewed: 116 (14 UL)
See detailEmbracing diversity in the digital transformation of primary healthcare
Lygidakis, Charilaos UL

Scientific Conference (2017, June 30)

The use of information and communication technologies for health constitutes a strategic ally to the sustainable development goals and attaining universal health coverage through enabling equitable access ... [more ▼]

The use of information and communication technologies for health constitutes a strategic ally to the sustainable development goals and attaining universal health coverage through enabling equitable access to high quality and affordable health care services. The omnipresence of mobile devices and sensors, the increasing availability of data and computational power, and the breakthroughs in imaging and genomics, are creating a perfect storm that is bound to transform health care profoundly. At the population level, the coordination of disease control and prevention programmes is facilitated, cost-effective interventions are implemented, and ultimately the quality of life of our communities is enhanced. EHealth also plays a significant role in the delivery of people-centred and integrated health services, empowers individuals to make informed decisions and self-manage their health needs. For the first time in history, the individual is placed at the centre, has timely and affordable access to data, knowledge and tools, and health care is tailored for his/her diverse background, context and needs. A second perspective to the digital revolution is how our own discipline is transformed. As technology is a catalyst for sustainable, large scale social change, health care has the opportunity to invest in inter-professional collaboration, and leverage a diverse range of expertise, stakeholders and resources to expand its horizons and tackle old and future challenges. [less ▲]

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See detailAn Enriched Quasi-Continuum Approach to Crack Propagation in Discrete Lattices
Rokos, Ondrej; Peerlings, Ron; Zeman, Jan et al

Scientific Conference (2017, June 14)

Detailed reference viewed: 86 (0 UL)
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See detailAn equation-free multiscale method applied to discrete networks
Beex, Lars UL; Kerfriden, Pierre

Scientific Conference (2017, June 06)

Detailed reference viewed: 63 (5 UL)
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See detailReduced basis Nitsche-based domain decomposition: a biomedical application
Baroli, Davide UL; Beex, Lars UL; Hale, Jack UL et al

Scientific Conference (2017, March 10)

Nowadays, the personalized biomedical simulations demand real-time efficient and reliable method to alleviate the computational complexity of high-fidelity simulation. In such applications, the necessity ... [more ▼]

Nowadays, the personalized biomedical simulations demand real-time efficient and reliable method to alleviate the computational complexity of high-fidelity simulation. In such applications, the necessity of solving different substructure, e.g. tissues or organs, with different numbers of the degrees of freedom and of coupling the reduced order spaces for each substructure poses a challenge in the on-fly simulation. In this talk, this challenge is taken into account employing the Nitsche-based domain decomposition technique inside the reduced order model [1]. This technique with respect to other domain decomposition approach allows obtaining a solution with the same accuracy of underlying finite element formulation and to flexibly treat interface with non-matching mesh. The robustness of the coupling is determined by the penalty coefficients that is chosen using ghost penalty technique [2]. Furthermore, to reduce the computational complexity of the on-fly assembling it is employed the empirical interpolation approach proposed in [3]. The numerical tests, performed using FEniCS[4], petsc4py and slepc4py [5], shows the good performance of the method and the reduction of computation cost. [1] Baroli, D., Beex L. and Bordas, S. Reduced basis Nitsche-based domain decomposition. In preparation. [2] Burman, E., Claus, S., Hansbo, P., Larson, M. G., & Massing, A. (2015). CutFEM: Discretizing geometry and partial differential equations. International Journal for Numerical Methods in Engineering, 104(7), 472-501. [3] E. Schenone, E., Beex,L., Hale, J.S., Bordas S. Proper Orthogonal Decomposition with reduced integration method. Application to nonlinear problems. In preparation. [4] A. Logg, K.-A. Mardal, G. N. Wells et al. Automated Solution of Differential Equations by the Finite Element Method, Springer 2012. [5] L. Dalcin, P. Kler, R. Paz, and A. Cosimo, Parallel Distributed Computing using Python, Advances in Water Resources, 34(9):1124-1139, 2011. http://dx.doi.org/10.1016/j.advwatres.2011.04.013 [less ▲]

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See detailSocially assistive robots for teaching emotional abilities to children with autism spectrum disorder
Pinto Costa, Andreia UL; Steffgen, Georges UL; Rodriguez Lera, Francisco Javier UL et al

Scientific Conference (2017, March)

Socially assistive robots, when used in a way that takes into consideration children’s needs and developmental characteristics, can be useful tools to enable children’s development. More specifically, due ... [more ▼]

Socially assistive robots, when used in a way that takes into consideration children’s needs and developmental characteristics, can be useful tools to enable children’s development. More specifically, due to their characteristics (predictability, simplicity, and repetition) robots can be especially helpful to teach emotional abilities to children with autism spectrum disorder (ASD). Previous research has provided preliminary evidence that robots can help children improve in some domains such as joint attention and imitation. However, no studies have examined how robots can be integrated in intervention protocols targeting the acquisition of emotional abilities in children with ASD. This paper presents a work in progress on an emotional ability training developed for children with ASD using the QT socially assistive robot. This training aims to test whether children with ASD can benefit from a robot-mediated training to improve emotional ability. [less ▲]

Detailed reference viewed: 511 (16 UL)
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See detailMultiphysics applications and computational challenges
Zilian, Andreas UL

Scientific Conference (2017, January 24)

Detailed reference viewed: 105 (5 UL)
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See detailXDEM: from HPC to the Cloud
Besseron, Xavier UL

Scientific Conference (2017, January)

Detailed reference viewed: 52 (3 UL)
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See detailReconstruction of Gene Regulatory Networks using an Error Filtering Learning Scheme
Tzortzis, Ioannis; Hadjicostis, Christoforos; Mombaerts, Laurent UL

Scientific Conference (2017)

One of the fundamental and most challenging problems in system biology is the reconstruction of gene regulatory networks from input-output data based on non-linear differential equations. This paper ... [more ▼]

One of the fundamental and most challenging problems in system biology is the reconstruction of gene regulatory networks from input-output data based on non-linear differential equations. This paper presents an approach to estimate the unknown nonlinearities and to identify the true network that generated the data, based on an error filtering learning scheme and a Lyapunov synthesis method. Unknown nonlinearities are modelled by networks using radial basis functions and model validation is performed by taking advantage of the so-called persistency of excitation of input signals, a condition that is shown to play a significant role in the problem of uncovering the true network structure. The proposed methodology and the theoretical results are validated through an illustrative example. [less ▲]

Detailed reference viewed: 89 (3 UL)
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See detailDigital History Projects As Boundary Objects
Kemman, Max UL

Scientific Conference (2017)

Detailed reference viewed: 77 (7 UL)
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See detailInterdisciplinary Ignorance
Kemman, Max UL

Scientific Conference (2017)

Detailed reference viewed: 75 (9 UL)
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Peer Reviewed
See detailUnpacking Collaboration in Digital History Projects
Kemman, Max UL

Scientific Conference (2017)

Detailed reference viewed: 73 (8 UL)
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See detailAn approach to information retrieval and question answering in the legal domain
Adebayo, Kolawole John UL; Di Caro, Luigi; Boella, Guido et al

Scientific Conference (2016, November 15)

We describe in this paper, a report of our participation at COLIEE 2016 Information Retrieval (IR) and Legal Question Answering (LQA) tasks. Our solution for the IR part employs the use of a simple but ... [more ▼]

We describe in this paper, a report of our participation at COLIEE 2016 Information Retrieval (IR) and Legal Question Answering (LQA) tasks. Our solution for the IR part employs the use of a simple but effective Machine Learning (ML) procedure. Our Question Answering solution answers "YES or 'NO' to a question, i.e., 'YES' if the question is entailed by a text and 'NO' otherwise. With recent exploit of Multi-layered Neural Network systems at language modeling tasks, we presented a Deep Learning approach which uses an adaptive variant of the Long-Short Term Memory (LSTM), i.e. the Child Sum Tree LSTM (CST-LSTM) algorithm that we modified to suit our purpose. Additionally, we benchmarked this approach by handcrafting features for two popular ML algorithms, i.e., the Support Vector Machine (SVM) and the Random Forest (RF) algorithms. Even though we used some features that have performed well from similar works, we also introduced some semantic features for performance improvement. We used the results from these two algorithms as the baseline for our CST-LSTM algorithm. All evaluation was done on the COLIEE 2015 training and test sets. The overall result conforms the competitiveness of our approach. [less ▲]

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See detailTowards Optimised Large Scale Deployments of Electric Bus Systems with On-Route Charging
Seredynski, Marcin; Khadraoui, Djamel; Viti, Francesco UL

Scientific Conference (2016, October)

Detailed reference viewed: 114 (10 UL)
Peer Reviewed
See detailA PAS-state constrained optimization formulation for the anticipatory network traffic control problem
Rinaldi, Marco UL; Tampère, Chris

Scientific Conference (2016, September)

Detailed reference viewed: 121 (2 UL)
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See detailSimultaneous Analysis of Strongly-Coupled Composite Energy Harvester-Circuit Systems Driven by Fluid-Structure Interaction
Zilian, Andreas UL; Ravi, Srivathsan UL

Scientific Conference (2016, July 27)

A specific class of energy harvester devices is investigated, that allow conversion of ambient fluid flow energy to electrical energy via flow-induced vibrations [1] of a piezo-ceramic composite structure ... [more ▼]

A specific class of energy harvester devices is investigated, that allow conversion of ambient fluid flow energy to electrical energy via flow-induced vibrations [1] of a piezo-ceramic composite structure positioned in the flow field. Potentially harmful flow fluctuations are harnessed to provide independent power supply to small electrical devices [2]. Such concept simultaneously involves the interaction of a composite structure and a surrounding fluid, the electric charge accumulated in the piezo-ceramic material and a controlling electrical circuit. In order to predict the efficiency and operational properties of these devices and to increase their robustness and performance, a predictive model of the complex physical system allows systematic computational investigation of the involved phenomena and coupling characteristics. A monolithic approach is proposed that provides simultaneous modelling and analysis of the harvester, which involves surface-coupled fluid-structure interaction, volume-coupled electro mechanics and a controlling energy harvesting circuit for applications in energy harvesting. A three dimensional space-time finite element approximation [3] is used for numerical solution of the weighted residual form of the governing equations of the flow-driven piezoelectric energy-harvesting device. This method enables time-domain investigation of different types of structures (plate, shells) subject to exterior/interior flow with varying cross sections, material compositions, and attached electrical circuits with respect to the electrical power output generated [4]. The space-time finite element model presented incorporates a novel method to enforce equipotentiality on the electrodes covering the piezoelectric patches, making the charge unknowns naturally appear in the formulation [5]. This enables to adapt any type of electrical circuit added to the electromechanical problem. [less ▲]

Detailed reference viewed: 130 (21 UL)
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See detailAnalyzing the correlation between commuting satisfaction and travelling utility
Sprumont, François UL; Astegiano, Paola; Viti, Francesco UL

Scientific Conference (2016, July 13)

The interest for travel satisfaction has rapidly grown during the past two decades. Since the development of Discrete Choice Theory, doing a trip was mostly described as a pure derived activity without ... [more ▼]

The interest for travel satisfaction has rapidly grown during the past two decades. Since the development of Discrete Choice Theory, doing a trip was mostly described as a pure derived activity without utility per se but nowadays many scholars have demonstrated that individuals might be satisfied in performing the trip itself. However, little is still known on the relation between the travelling utility and the stated satisfaction for a specific trip. The objective of this paper is to analyse the relation between the stated commuting satisfaction and the utility of the associated trip thanks to the Logsum function, which is often used to represent the aggregated utility of a set of travel alternatives. The results of a travel survey implemented at the University of Luxembourg in 2012, show that the utility function, expressed through its Logsum, is positively correlated with the stated commuting satisfaction. While the Logsum function of the travelling utility might, to some extent, approximate the travelling satisfaction, some variations in the correlation magnitude, due to context particularities and socio-demographic attributes, are observed and discussed in this study. [less ▲]

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See detailA dynamic route swapping and control algorithm that maximises network capacity accounting for node constraints and blocking back
Viti, Francesco UL; Huang, Wei; Smith, Mike

Scientific Conference (2016, July)

Detailed reference viewed: 64 (1 UL)
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See detailPOD-based reduction methods, the Quasicontinuum Method and their Resemblance
Beex, Lars UL; Schenone, Elisa; Hale, Jack UL

Scientific Conference (2016, June 27)

Detailed reference viewed: 118 (11 UL)
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See detailNumerical Modeling of Flow-Driven Piezoelectric Energy Harvesters
Ravi, Srivathsan UL; Zilian, Andreas UL

Scientific Conference (2016, June 09)

A specific class of energy harvester devices for renewable energy resources is investigated, that allow conversion of ambient fluid flow energy to electrical energy via flow-induced vibrations of a piezo ... [more ▼]

A specific class of energy harvester devices for renewable energy resources is investigated, that allow conversion of ambient fluid flow energy to electrical energy via flow-induced vibrations of a piezo-ceramic composite structure positioned in the flow field [3,4]. In this way, potentially harmful flow fluctuations are harnessed to provide independent power supply to small electrical devices. In order to harvest energy from fluid flows by means of piezoelectric materials the kinetic energy of the fluid first has to be transformed to cyclic straining energy of the piezoelectric material which is then transformed to electrical energy under the presence of an attached electrical circuit representing the powered electrical device or charged battery. This energy converter technology simultaneously involves the interaction of a composite structure and a surrounding fluid, the electric charge accumulated in the piezo-ceramic material and a controlling electrical circuit. In order to predict the efficiency and operational properties of such future devices and to increase their robustness and performance, a mathematical and numerical model of the complex physical system is required to allow systematic computational investigation of the involved phenomena and coupling characteristics. The research is devoted to introducing a monolithic approach that provides simultaneous modeling and analysis of the coupled energy harvester, which involves surface-coupled fluid-structure interaction, volume-coupled piezoelectric mechanics and a controlling energy harvesting circuit for applications in energy harvesting. The weak form of the governing equations is discretized by the space-time finite element method based on a mixed velocity-stress/rate form of the potential-dielectric displacement framework. The space-time finite element [2,3] model incorporates a novel method to enforce equipotentiality on the electrodes covering the piezoelectric patches, making the charge unknowns naturally appear in the formulation. This enables to adapt any type of electrical circuit added to the electromechanical problem. To validate the formulation, the case of piezoelectric triple layer EHD driven by base excitations, as described in [1] is chosen. The closed-form solution from [1] is compared to numerical solution proposed in this work. The variation of the electric potential through the thickness of the piezoelectric patch, assumed to be linear in many closed-form solutions, is shown to be quadratic in nature. The research contributes to the mathematical modeling and numerical discretization of complex multi- physics system in an efficient way which facilitates an ideal basis for precise and transient coupling. This may lead to improved convergence and numerical efficiency in comparison with portioned approaches. This methodology also provides new insights and in-depth understanding on design requirements on such energy harvesting devices in terms of their robustness and efficiency. [less ▲]

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See detailWeakening the tight coupling between geometry and simulation in isogeometric analysis
Bordas, Stéphane UL; Tomar, Satyendra UL; Atroshchenko, Elena et al

Scientific Conference (2016, June 05)

In the standard paradigm of isogeometric analysis, the geometry and the simulation spaces are tightly integrated, i.e. the same non-uniform rational B-splines (NURBS) space, which is used for the geometry ... [more ▼]

In the standard paradigm of isogeometric analysis, the geometry and the simulation spaces are tightly integrated, i.e. the same non-uniform rational B-splines (NURBS) space, which is used for the geometry representation of the domain, is employed for the numerical solution of the problem over the domain. However, there are situations where this tight integration is a bane rather than a boon. Such situations arise where, e.g., (1) the geometry of the domain is simple enough to be represented by low order NURBS, whereas the unknown (exact) solution of the problem is sufficiently regular, and thus, the numerical solution can be obtained with improved accuracy by using NURBS of order higher than that required for the geometry, (2) the constraint of using the same space for the geometry and the numerical solution is particularly undesirable, such as in the shape and topology optimization, and (3) the solution of the problem has low regularity but for the curved boundary of the domain one can employ higher order NURBS. Therefore, we propose to weaken this constraint. An extensive study of patch tests on various combinations of polynomial degree, geometry type, and various cases of varying degrees and control variables between the geometry and the numerical solution will be discussed. It will be shown, with concrete reasoning, that why patch test fails in certain cases, and that those cases should be avoided in practice. Thereafter, selective numerical examples will be presented to address some of the above-mentioned situations, and it will be shown that weakening the tight coupling between geometry and simulation offers more flexibility in choosing the numerical solution spaces, and thus, improved accuracy of the numerical solution. Powered by [less ▲]

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See detailLinear smoothing over arbitrary polytopes for compressible and nearly incompressible linear elasticity
Natarajan, Sundararajan; Tomar, Satyendra UL; Bordas, Stéphane UL et al

Scientific Conference (2016, June)

We present a displacement based approach over arbitrary polytopes for compressible and nearly incompressible linear elastic solids. In this approach, a volume-averaged nodal projection operator is ... [more ▼]

We present a displacement based approach over arbitrary polytopes for compressible and nearly incompressible linear elastic solids. In this approach, a volume-averaged nodal projection operator is constructed to project the dilatational strain into an approximation space of equal or lower-order than the approximation space for the displacement field, resulting in a locking-free method. The formulation uses the usual Wachspress interpolants over arbitrary polytopes and the stability of the method is ensured by the addition of bubble like functions. The smoothed strains are evaluated based on the linear smoothing procedure. This further softens the bilinear form allowing the procedure to search for a solution satisfying the divergence- free condition. The divergence-free condition of the proposed approach is verified through systematic numerical study. The formulation delivers optimal convergence rates in the energy and L2-norms. Inf-sup tests are presented to demonstrated the stability of the formulation. [less ▲]

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See detailVirtual-power-based quasicontinuum methods for discrete dissipative materials
Beex, Lars UL; Bordas, Stéphane UL

Scientific Conference (2016, June)

Detailed reference viewed: 87 (2 UL)
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See detailNetwork observability information maximization through ad-hoc route enumeration approaches
Rinaldi, Marco UL; Corman, Francesco; Viti, Francesco UL

Scientific Conference (2016, June)

Detailed reference viewed: 65 (2 UL)
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See detailVirtual-power-based quasicontinuum methods for discrete dissipative materials
Beex, Lars UL

Scientific Conference (2016, June)

In this presentation, the formulation of the virtual-power-based QC framework will be outlined for an elastoplastic truss lattice. Subsequently, the framework is applied to an actual discrete material.

Detailed reference viewed: 69 (3 UL)
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See detailPOD-based Reduction Methods, the Quasicontinuum Method and their Resemblance
Schenone, Elisa; Hale, Jack UL; Beex, Lars UL

Scientific Conference (2016, June)

POD-based reduction methods and the quasicontinuum method share two similar reduction steps to increase the computational speed of large mechanical models. Here, they are compared with each other.

Detailed reference viewed: 91 (8 UL)